The Anatomy of sea turtles


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The Anatomy of sea turtles
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NOAA technical memorandum NMFS-SEFSC ;
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vii, 172 p. : chiefly ill. ; 28 cm. +
Wyneken, Jeanette, 1956-
Southeast Fisheries Science Center (U.S.)
Southeast Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, U.S. Dept. of Commerce
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Miami, Fla
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Sea turtles -- Anatomy -- Handbooks, manuals, etc   ( lcsh )
Sea turtles -- Morphology -- Handbooks, manuals, etc   ( lcsh )
bibliography   ( marcgt )
handbook   ( marcgt )
technical report   ( marcgt )
federal government publication   ( marcgt )
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Includes bibliographical references (p. 166-168) and index.
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System requirement for accompanying CD-ROM: Windows Pentium and Macintosh PowerPC computers with at least 32MB available application RAM; a fast CD-ROM drive (24X or higher); a monitor capable of viewing at least 800 X 600 pixels; QuickTime must be installed to view the videos in the program; Adobe Acrobat Reader must be installed to read the PDF file; Sound card and speakers.
General Note:
"December 2001."
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CD-ROM contains an Adobe Acrobat PDF document and a companion 4-part video.
Statement of Responsibility:
by Jeanette Wyneken.

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University of Florida
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oclc - 49846933
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lcc - QL666.C536 W965 2001
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December 2001U. S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, FL 33149 The Anatomy of Sea Turtles The Anatomy of Sea TurtlesJeanette Wyneken, Ph.D.Illustrated by Dawn Witherington NOAA Technical Memorandum NMFS-SEFSC-470


NOAA T echnical Memorandum NMFS-SEFSC-470 THE ANA T OMY OF SEA TUR TLES by Jeanette W yneken, Ph.D. U. S. DEP AR TMENT OF COMMERCE Donald L. Evans, Secr etary NA TIONAL OCEANIC AND A TMOSPHERIC ADMINISTRA TION Conrad C. Lautenbacher, Jr., Administrator NA TIONAL MARINE FISHERIES SER VICE W illiam T Hogarth, Assistant Administrator for Fisheries December 2001 Unpublished reports are used for documentation and timely communication of preliminary results, interim reports, or special-purpose information, and have not received complete formal review editorial control, or detailed editing.


The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material herein or which has as its purpose any intent to cause directly or indirectly the advertised product to be used or purchased because of NMFS publication. Correct citation of this report is: Wyneken, J. 2001. The Anatomy of Sea Turtles. U.S. Department of Commerce NOAA Technical Memorandum NMFS-SEFSC-470, 1-172 pp. The scientific contents of the The Anatomy of Sea Turtles 2001 Jeanette Wyneken. Copyright claimed on pages iii-172 exclusive of page 4 Copies of this report can be obtained from: National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, FL 33149 or National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 (503) 605-6000 (800) 553-6847 (rush orders) ii NOTICE


The Anatomy of Sea Turtles The Anatomy of Sea TurtlesJeanette Wyneken, Ph.D.Illustrated by Dawn Witherington




The need for an up-to-date guide to the anatomy of sea turtles became clear toward the end of the 1900s. Increasing numbers of individuals developed the interest, talents, and techniques to study the biology of sea turtles, contend with their illnesses and injuries, and address the nature of sea turtle mortalities. This manual was written in response to these needs and was designed to be accessible to a variety of users. It provides a fundamental background, reference photos of normal anatomy, and diagrams to guide novice or professional biologists, stranding personnel, and veterinarians. Species identification, standard dissection techniques, standard measurements, and basic anatomy are covered with a diverse audience in mind. While this manual does not serve as a necropsy guide, it may serve as a reference when conducting necropsies. It is designed particularly with the understanding that many users will be working with it in the field or under less-than-ideal conditions. The Anatomy of Sea Turtles is organized so that it can be used either as a guide to dissection or as an anatomical reference to species identification, standard methods, and dissection (pp. 1-42) or as an anatomical reference to sea turtle structures or systems. Most of the photos in this guide are by the author. However, several individuals contributed pictures that enhanced the quality of the manual. These include Larisa Avens, George Balazs, Peter Bennett, Beth Chittick, Larry Crowder, Bill Dailey, Sheryan Epperly, Craig Harms, Eve Haverfield, Bruce Homer, Chris Johnson, Ursula Keuper-Bennett, Joanne Braun McNeill, Anne Meylan, David Owens, Denise Parker, Donna Shaver, Tom Smoyer, J. Vasconcelos, and Wendy Teas. Access to specimens, dissection assistance, and/or comments on drafts of the manual were provided by George Balazs, Ruth Boettcher, Mike Bresette, Brian Cousin, Lisa Csuzdi, Nancy DiMarco, Sheryan Epperly, Kristin Fick, Allen Foley, Jerris Foote, T.H. Frazzetta, Ellis Greiner, Craig Harms, Kristin Hart, Hector Horta, Elliott Jacobson, Chris Johnson, Ken Kardong, Jennifer Keller, Kate Kelso, Greg Lewbart, Peter Lutz, Charles Manire, Carol Hardy McFadden, Joanne Braun McNeill, Nancy Mette, Jeff Miller, Debra Moore, Steve Morreale, David Owens, Joe Parsons, Robert Prescott, Peter C. H. Pritchard, Tony Redlow, Anders Rhodin, Kurt Rusenko, Cheryl Ryder, Michael Salmon, Karrie Singel, Melissa Snover, Trish Sposato, Fred Steinberg, Kelly Stewart, Wendy Teas, Mike Walsh, James Weege, Pat W ells, Donna Weyrich, Dale Wilke, Blair Witherington, Wayne Witzell, and Larry Wood. The Cayman Turtle Farm, Chelonian Research Institute, Florida Fish and Wildlife Conservation Commission, Gumbo Limbo Environmental Center, Harbor Branch Oceanographic Institution, The Marinelife Center of Juno Beach, Mote Marine Laboratory, Philadelphia Academy of Sciences, National Marine Fisheries Service-Beaufort Laboratory, National Marine Fisheries Service-Miami Laboratory, North Carolina Wildlife Commission, University MRI, Inc., and the U.S. Fish and Wildlife Service provided access to specimens and logistical help. Many individuals provided thoughtful discussions during the preparation of this manual and The Anatomy of Sea Turtles video. The quality and coverage of The Anatomy of Sea Turtles was greatly improved by their attention and suggestions. This manual’s illustrations and layout are by Dawn Witherington. v PREFACE


The following people contributed photos that enhanced the quality of this manual. Where known, turtle tag numbers or their identifications are also provided. Ursula Keuper-Bennett and Peter Bennett: Figs. 11, Tutu; Fig. 20, Ake Beth Chittick: Fig. 145 Larry Crowder: Fig. 141 Bill Dailey: Fig. 21 Craig Harms: Figs. 81, 161, 187 Bruce Homer: Fig. 176 Chris Johnson: Figs. 9, 17 Heather Kalb and David Owens: Fig. 234 Joanne Braun McNeill: Fig. 15 Anne Meylan: Fig. 77 Peter C. H. Pritchard: Fig. 189 Tom Smoyer (Harbor Branch Oceanographic Institution): Figs. 10, 12, 13, 14, 19, 31, 45, 58, 70, 71, 90, 106, 229 J. Vasconcelos: Fig. 24 vi PHOTOGRAPHIC CREDITS


Basic Terminology and Characters for Species Identification...............................................................1 Species Identification......................................................................................................... ....................4 Skull Anatomy ................................................................................................................. ......................8 Species Identification from Skulls............................................................................................. ............13 Rhamphotheca Structure......................................................................................................... ...............26 Standard Measurements.......................................................................................................... ...............28 Methods of Dissection ......................................................................................................... ..................33 Skeletal Anatomy............................................................................................................... ....................43 Muscle Anatomy................................................................................................................. ...................59 Circulatory Anatomy............................................................................................................ ..................74 Lung and Airway Anatomy ....................................................................................................... ............105 Gastrointestinal Anatomy ...................................................................................................... ................108 Glands ........................................................................................................................ ............................115 Nervous System................................................................................................................. .....................125 Sense Organs................................................................................................................... .......................146 Urogenital System.............................................................................................................. ....................153 Selected Bibliography.......................................................................................................... ...................166 Index.......................................................................................................................... ............................169 vii TABLEOFCONTENTS


BASIC TERMINOLOGY AND CHARACTERS 1 The Anatomy of Sea Turtles Anatomical TerminologyThere are several terms used here that describe the spatial relationships of structures. Below, these are defined specifically for sea turtles (Figs. 1-2). Dorsal is toward the top of the shell (the carapace). Ventral is toward the plastron. Anterior is toward the head. Posterior is toward the tail. Medial is toward the midline. Lateral is away from the midline, toward the sides. Proximal is close to the body or the start of a structure. Distal is away from the body or main structure. Deep to is underneath a structureCharacters for Species IdentificationSea turtle identification, from external characters, is based upon the scales on the head, form of the jaws, the number of claws on the feet, and the numbers and arrangement of the plates or scutes on the shell. The scutes of the carapace (the top shell) are numbered from front to back (Fig. 3). The primary scutes (Fig. 4) used as key characteristics are the marginals laterals (costal) vertebrals and nuchal as well as the inframarginal or bridge scutes. The bottom shell is the plastron It also has distinct scute patterns, but these are used more often as landmarks for internal structures than for species identification (Fig. 5). From anterior to posterior, the intergular scute is closest to the neck, then (in order) are the gular humeral pectoral abdominal femoral and the anal scutes. Some individuals have a single unpaired interanal scute that is found between or posterior to the anal scutes. ventral anterior posterior dorsal proximal distal medial lateral 2 3 4 5 1 Fig. 2. Relative anatomical position. Fig. 1. Anatomical terminology. Fig. 3. Numbering the carapace scutes.


Scutes of the carapace and plastron. The lateral scutes are also known as costals or pleurals. The last marginal scutes on each side are termed supracaudals or postcentrals (Fig. 4). The scutes between the plastron and the carapace are the inframarginals (Fig. 5). While the number of inframarginals is somewhat variable, the most common count is often listed as a key characteristic. Cheloniidae (hard-shelled sea turtles) are characterized by the scales on the head, carapace, and inframarginal scute patterns and numbers, as well as the numbers of claws on the flippers (Figs. 6-7). Most species have 2 claws. Claw I is usually larger than claw II and becomes strongly curved in adult males. The number of claws on the front and hind limbs is the same. claw I CHARACTERS FOR SPECIES IDENTIFICATION The Anatomy of Sea Turtles 2 intergular gular humeral inframarginal pectoral abdominal femoral anal supracaudal nuchal 1st marginal vertebral 1st costal Fig. 4. Scutes of the carapace. Fig. 5. Scutes of the plastron and bridge. Fig. 6. Position and numbering of claws. Fig. 7. The single claw occurs on the first digit. No claw forms on the second digit.


CHARACTERS FOR SPECIES IDENTIFICATION The Anatomy of Sea Turtles 3Leatherbacks lack both distinctive head scales as adults and have minimal keratin covering on the jaws. The hard-shelled sea turtles have keratinous scales on the dorsal and lateral head that are used in identification of species (Fig. 8). The prefrontal scales occur in pairs. One or more supernumerary scales may occur along the midline and separate the pairs. Other head scales ( supraocular postocular frontal frontoparietal parietal interparietal temporal and tympanic scales ) may vary slightly in form but not in position relative to one another. In some cases, individual variations in the head scales can be used to identify individual turtles. Several internal bony and jaw (rhamphotheca) characters also may be used for species identification. These are described later (Species Identification from Skulls, pp. 13-25; Rhampotheca Structure, pp. 26-27; Skeletal Anatomy, pp. 50-51). prefrontal scales supernumery scale supraocular scales frontal scale frontoparietal scale parietal scales postocular scales temporal scales tympanic scales interparietal scale Fig. 8. Head scales of cheloniid turtles. The major sets of scales used in species identification are the prefrontals. There are often supernumerary scales (multiple extra scales) between the prefrontals. These lack pattern and are usually small. The other labeled scales serve as landmarks. A key to the species is found on the next page. It summarizes species identification using external characteristics.


SPECIESIDENTIFICATION The Anatomy of Sea Turtles 4 4 inframarginal scutes without pores 4 inframarginal scutes without pores 4 inframarginal scutes with pores 4 inframarginal scutes with pores scutes imbricated (overlapping)head carapace plastron4 lateral scutes 4 lateral scutesGreen turtle Chelonia mydas Hawksbill Eretmochelys imbricata Kemp’s ridley Lepidochelys kempii Olive ridley Lepidochelys olivacea Leatherback Dermochelys coriacea5 lateral scutes 6 or more lateral scutes 5 lateral scutes ridges no scutes6 or more vertebral scutes1 pair of prefrontal scales 2 pairs of prefrontal scales more than 1 pair of prefrontal scales more than 1 pair of prefrontal scales more than 1 pair of prefrontal scales no scales Loggerhead Caretta caretta3 inframarginal scutes without pores


SPECIES IDENTIFICATION The Anatomy of Sea Turtles 5 Species IdentificationSea turtles can be separated into the hard-shelled (cheloniid) and the leathery-shelled (dermochelyid) species. There is just one dermochelyid species, the leatherback, Dermochelys coriacea (Figs. 9-10). It is black with white speckling. Five dorsal ridges run the length of the carapace, two ridges form the margins, and few ridges occur ventrally. A notch occurs in each side of the upper jaw and the limbs lack claws. The cheloniids can be distinguished from one another by the scales on top of the snout, called the prefrontals and by the scutes on the carapace. The green turtle, Chelonia mydas (Figs. 11-13), has one pair of prefrontal scales (Fig. 12). The carapace is smooth with 4 pairs of lateral scutes. Carapace color changes with age. It is black in hatchlings, then turns brown and tan in juveniles, and in adults, it is olive or gray-green, sometimes with speckles of yellow and brown. The plastron is white in hatchlings. It turns creamy yellow, sometimes temporarily pink or gray depending on the population. Adults have a creamy yellow plastron except in the more melanistic green turtles (referred to as black turtles) found in some Pacific waters. The green turtle has one claw on each limb. There are 4 inframarginal scutes on each side and two Rathke’s pores, one each in the axillary and inguinal scales (see Glands, pp. 122-123). Fig. 9. Dermochelys coriacea adult. Fig. 11. Chelonia mydas adult. Fig. 12. Chelonia mydas juvenile. Fig. 10. Dermochelys coriacea hatchling. Fig. 13. Chelonia mydas hatchling.


SPECIES IDENTIFICATION The Anatomy of Sea Turtles 6 The remaining species have 2 pairs of prefrontal scales (Fig. 8) and, as young, they have keels (ridges) on their shells. The loggerhead, Caretta caretta (Figs. 14-17), has a large head and brown carapace with 5, or sometimes 4, lateral scutes. The nuchal scute (the marginal just dorsal to the neck) is in contact with the first lateral scute.In hatchlings, the carapace is brown with various shades of grey (Fig. 14). The plastron of hatchlings is creamy to brown. In juveniles to adults it is creamy and tan. The carapaces of juveniles (Fig. 16) develop streaks of yellow and tan. Sometimes the scutes of juveniles slightly overlap one another at their margins. In adults, there is no overlap of scutes. The carapace is primarily brown with occasional individuals retaining some tans or even black (Fig. 17). The shells of loggerheads often host large epibiont communities. Loggerheads have two claws on each limb. The hawksbill, Eretmochelys imbricata as a hatchling, is dark mahogany brown on both the carapace and the plastron (Fig. 18). As the turtle grows, the head elongates and the carapace develops a distinctive pattern of yellow, black, tan and brown radiating through the scutes (Fig. 19). This color persists though adulthood. The nuchal scute does not touch the first lateral scute in hawksbills. This distinguishes the hawksbill carapace from the loggerhead pattern. The head of the hawksbill is nearly twice as long as it is wide and has a long narrow beak or rhamphotheca (Fig. 20). Hawksbills have two claws on Fig. 16. Car etta car etta immature. Immature loggerheads often have sharp keels on their vertebral scutes and posterior marginal. These recede with largersize and age so that loggerheads found in coastal waters often bear little of or no signs of the keels. Fig. 17. Car etta car etta adult. The jaws have thick, robust rhampotheca (beak-like structures) for crushing food. Fig. 15. Car etta car etta plastron. Loggerheads often have 3 inframarginals however, this characteristic is variable. Fig. 14. Car etta car etta hatchling.


SPECIES IDENTIFICATION The Anatomy of Sea Turtles 7 The last two species that occur in U.S. waters are the ridleys (Figs. 21-24). These turtles are mostly gray in color.The Kemp's ridley, Lepidochelys kempii, occurs in east coast waters. The olive ridley, Lepidochelys olivacea occurs in Pacific and South Atlantic waters (but occasionally strays into tropical North Atlantic regions). The hatchlings of both species are gray-brown. The carapace assumes a nearly round appearance as the turtle grows and the marginal scutes become wide (Fig. 21). There are 4 (sometimes 3) inframarginal scutes. Characteristic pores are found within each inframarginal scute (Fig. 22) in both ridley species. Ridley turtles have two claws on each limb. Fig. 18. Er etmochelys imbricata hatchling (left) and Car etta car etta hatchling (right). Note that the nuchal scute touches the first lateral in loggerheads but not in hawksbills. Fig. 19. Er etmochelys imbricata immature. The narrow head and imbricate (overlapping) scutes of the hawksbill are clear. Fig. 21. Lepidochelys kempii adult Fig. 20. Er etmochelys imbricata adult.


Kemp's ridley turtles are dark grey to grey-green in color. They have 5 lateral scutes (4-6 is common). Olive ridleys turtles are dark grey. They typically have more than 6 normally aligned lateral scutes, 6 or more normally aligned vertebral scutes (Fig. 23) and many supraoccular scales (Fig. 24).Skull AnatomyThe skull is organized into an inner braincase, the neurocranium, which houses the brain and an outer bony superstructure, the splanchnocranium The anterior splanchnocranium along with the mandibles form the jaws. The splanchnocranium also houses the sense organs and provides the muscle attachment sites for jaw, throat and neck muscles. The braincase is found along the midline, internal to the skull roof, snout, and jaw bones of the splanchnocranium. The external bones of the splanchnocranium (Fig. 25) are the same in all species, however their specific form and some articulations differ. Skull shape and the patterns of bones of the palate (roof of mouth; Figs. 26-27) are diagnostic for species identification. Lateral bones (Fig. 28) are important landmarks for locating internal structures. The jaws (Fig. 26) and the neurocranium (Fig. 29), also are composites of several bones. SPECIES IDENTIFICATION/SKULL ANATOMY The Anatomy of Sea Turtles 8 Fig. 22. Lepidochelys inframarginals with Rathke’s pores. Fig. 24. Lepidochelys olivacea adult Fig. 23. Lepidochelys hatchlings L. kempii (right) has just 5 lateral and vertebral scutes while L. olivacea (left) has 6 or more lateral and vertebral scutes.


SKULL ANATOMY The Anatomy of Sea Turtles 9 Figs. 26a and 26b. Ventral bones of the skull (with the hyoid skeleton of the throat removed) are shown with the lower jaw and anterior neck vertebrae articulated. Both the upper and lower jaws are composed of multiple bones. The posterior braincase, part of the neurocranium, articulates with the cervical vertebrae. The vertebrae are composed of several parts: a vertebral body or centrum located ventrally and dorsal arch elements. C1 C4: Cervical vertebrae. Figs. 25a and 25b. The dorsal and lateral bones are identified here. With the exception of the supraoccipital, these are bones of the splanchnocranium. postorbital jugal frontal maxilla prefrontal external nares premaxilla parietal squamosal supraoccipital palatine atlas C1 basisphenoid splenial angular maxillary dentary auditory canal axis C2 C3 C4 pterygoid aba b


SKULL ANATOMY The Anatomy of Sea Turtles 10 vomer maxilla paletine internal nares premaxilla NOTE: Maxillae do not touch NOTE: Pterygoid processes. Compare with L. olivacea a b Figs. 27a and 27b. The specific articulations and forms of the bones are characteristic of each species. The bones that make up the palate are frequently used as key characteristics. For example, in this ridley skull, the vomer prevents the maxillae from touching. In the loggerhead, a grossly similar skull, the vomer does not reach the premaxillae, so the maxillaries articulate. The pterygoid process shape and position are also key characteristics.


SKULL ANATOMY The Anatomy of Sea Turtles 11 Figs. 28a and 28b. The lateral bones, identified on this cheloniid skull, vary in form with species. The eye would be housed in the orbit and the auditory canal (ear) would occupy the notch posterior to the quadratojugal. Fig. 29. The lower jaw is a composite of the dentary, angular, surangular, prearticular, splenial (not shown) and articular bones. The cartilaginous portion is Meckel’s cartilage; it is found in the Meckelian groove in life. postorbital orbit parietal squamosal bone auditory canal jugal quadrate quadratojugal bone maxilla premaxilla dentary Meckelian groove prearticular angular surangular articular a b


SKULL ANATOMY The Anatomy of Sea Turtles 12 prootic opisthotic parietal postorbital squamosal stapes pterygoid rostrum basisphenoidale Figs. 30a and 30b. The neurocranium is partially exposed by the removal of the jugal, quadratojugal, and quadrate of a hawksbill skull. The braincase is small and housed internal to the skull roof. Anterior bones (rostrum basisphenoidaleand pterygoid) and lateral bones (prootic and opisthotic) form walls of the braincase. a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 13 Species Identification from SkullsThe following descriptions are based upon bony characteristics alone and do not include other diagnostic features of the scales or the form of the rhampotheca (keratinaceous beak, see Rhamphotheca Structure, pp. 26-27). Chelonia mydas (Figs. 31 33). The skull is rounded with a short snout and shallow parietal notches (Fig. 31).The upper jaw is described by a smooth U-shaped outline; the palate between the margins of the upper jaw and the internal nares (the alveolar surface) has a pair of ridges that run parallel to the outer edge of the jaw (Fig. 32). The lower jaw, has a ridge running parallel to the inner surface (Fig. 33) and a midline cusp. Figs. 31a and 31b. Chelonia mydas lateral view. a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 14 Figs. 32a and 32b. Chelonia mydas dorsal and ventral skull. Note ridges on palate at arrows. b a


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 15 Figs. 33a and 33b. Chelonia mydas ventral skull and lower jaw. Midline cusp of lower jaw at arrow. U-shaped palate a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 16 Caretta caretta (Figs. 34 and 35). The head of the loggerhead is relatively large, wide posteriorly, and the snout tapers anterior to the orbits. The parietal notches (wide U-shape emarginations formed by the posterior borders of the squamosal, parietal and supraoccipital bones) are large (Fig. 34). The jaws are robust and shaped like a wide V. Loggerheads have a relatively long secondary palate. (The secondary palate is the shelf of bone that separates or partially separates food and air passages.) The palate lacks alveolar ridges and the two maxillary bones contact one another posterior to the premaxillary bones (Fig. 35). Figs. 34a and 34b. Car etta car etta dorsal skull and lower jaw. Parietal notches are at arrows. a b parietal notch


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 17 Figs. 35a and 35b. Car etta car etta ventral skull and lower jaw. Note that the two maxillary bones touch at the middle of the palate. a b secondary palate


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 18 Lepidochelys kempii (Fig. 36) The skull is similar in overall shape to that of the loggerhead but can be distinguished from the loggerhead by the features of the palate. The Kemp’s ridley skull is roughly triangular in shape. The parietal notches are well developed (Fig. 36). The snout tapers anterior to the orbits. The jaws are shaped like a wide curved V and there is a relatively long secondary palate. The palate has longitudinal alveolar ridges and the two maxillary bones are separated by the vomer which extends anteriorly to articulate with the premaxillary bones (Figs. 27 and 36). The orbits are relatively small when compared with other species and each has a ridge of bone along its dorsal margin that extends laterally from the anterior portion of the postorbital bone. Figs. 36a and 36b. Lepidochelys kempii dorsal and ventral skull. a b alveolar ridges


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 19 Lepidochelys olivacea (Figs. 37-39) The olive ridley skull is similar in shape to skulls of the loggerhead and Kemp’s ridley. It is roughly triangular in shape, wide posteriorly, and has deep parietal notches. The jaws are shaped like a wide V.The palate lacks alveolar ridges. The two maxillary bones are separated by the vomer which articulates with the premaxillary bones. The orbits are larger than in L. kempii (Figs. 39-40) and the pterygoid bones are broad at their narrowest point when compared with other species. Figs. 37a and 37b. Lepidochelys olivacea dorsal skull Figs. 38a and 38b. Lepidochelys olivacea ventral skull. The pterygoid bone of the olive ridley is proportionately wider and the pterygoid processes are more pronounced than in the Kemp’s ridley. pterygoid bone pterygoid process palatine bone a b a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 20 Figs. 39a and 39b. Lepidochelys olivacea lateral skull. When measured across its longest axis, the orbits of L. olivacea are proportionately larger than those of L. kempii. Figs. 40a and 40b. Lepidochelys kempii lateral skull. Note the proportionally smaller orbit and slightly more hooked snout. a b a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 21 Eretmochelys imbricata (Figs. 41-42) The hawksbill skull is long and narrow in all but the youngest turtles (hatchlings). The length is approximately equal to twice the width (measured at the skull's widest part; Fig. 42). Hawksbill skulls have deep parietal notches and the snout tapers to a point. The jaws are V-shaped and narrow (Fig. 41). The secondary palate is well developed and the internal nares are situated in the anterior third of the mouth. The two maxillary bones are separated by the vomer which extends anteriorly to articulate with the premaxillary bones (Fig. 42). Figs. 41a and 41b. Er etmochelys imbricata dorsal skull and lower jaw with rhampotheca. The jaws are very narrow and V-shaped.parietal notch is deep “V”shapea b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 22 Figs. 42a and 42b. Er etmochelys imbricata ventral skull and lower jaw. The skull is longer and narrower than that of any other species. The secondary palate is long so that the internal nares (arrow) are relatively far back. W L ~ 2X W=La b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 23 Dermochelys coriacea (Figs. 43 44). Leatherback skulls are unlikely to be mistaken for those of any other species. The skull is wide and rounded anteriorly with large orbits; there are no parietal notches (Fig. 43). The bones articulate loosely; there is little or no secondary palate (Fig. 44). The margins of the jaws are sharp and possess notches. There are pointed cusps on the anterior maxillary bones. The lower jaw comes to a dorsally directed point at the mandibular symphysis (where the two halves of the lower jaw join). The lower jaw has a cartilaginous portion medial to the dentary. Figs. 43a and 43b. Dermochelys coriacea dorsal skull and lower jaw. The bones fit together more loosely than in other species. The leatherback skull and skeleton has been described as neotenic (having embryonic characteristics) in form because of the lack of bony fusions. a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 24 Figs. 44a and 44b. Dermochelys coriacea ventral skull and lower jaw. Note the lack of a secondary palate and the loose articulations of the bones. notch a b


SPECIES IDENTIFICATION FROM SKULLS The Anatomy of Sea Turtles 25 Fig. 45. Skulls of all the species found in US waters. Clockwise from top right: Dermochelys coriacea (a), Er etmochelys imbricata (b), Chelonia mydas (c), Lepidochelys olivacea (d), Lepidochelys kempii (e), Car etta car etta (f). The hawksbill, gr een turtle and Kemp's ridley skulls are from immature animals, others are from adults. a b c d f e


The Anatomy of Sea Turtles 26 RHAMPHOTHECA STRUCTURE Chelonia mydasRhamphotheci Upper RhamphothecaLower Rhamphotheca•Snout rounded, outer keratin smooth and delicately built. •Edges are outlined by serrations and spike-like cusps. •Upper rhamphotheca serrated, short, pointed cusps. •Inner surface with vertically aligned ridges. •Lower rhamphotheca is serrated with vertical spike-like processes. •Parallel inner ridge with row of smaller cusps. •Midventral ridge without spikes connects the two. •Alveolar surface has two depressions to either side of the midline ridge. Rhamphotheca (beak)The rhamphotheci are the keratinous beaks of the upper and lower jaws in cheloniids. They cover the maxillary, premaxillary, and vomer bones of the upper jaw, and the dentary of the lower jaw. They differ with diet and can be used to identify species. Several terms are used to describe the positions of parts of the mouth or rhamphotheci. Alveolar refers to the surfaces and edges of the jaws where teeth would be found in nonchelonian reptiles. Palatal refers to the horizontal surface forming the roof of the mouth. Buccal refers to the portion of the lower plate next to the tongue. Below, species-specific characteristics of the rhamphotheci (Fig. 46), useful in species identification, are illustrated and described.RhamphotheciUpper RhamphothecaLower Rhamphotheca Eretmochelys imbricata •Rhamphotheca moderately built. •Snout narrow and pointed with sharp alveolar edges. •Upper rhamphotheca’s palatal portion is mostly smooth. •Slight ridge, parallel to the maxillae; ridge may wear in older turtles. •Lower rhamphotheca is narrow and smooth. •Triangular process extends anteriorly from the buccal (posterior) margin. Fig. 46. Rhamphotheca characteristics by species.


The Anatomy of Sea Turtles 27 RHAMPHOTHECA STRUCTURE Rhamphotheci Upper RhamphothecaLower Rhamphotheca Caretta caretta •Rhamphotheci robustly constructed with sharp alveolar edges. •In young, upper and lower jaw come to a point. •Upper rhamphotheca: palatal portion is wide and forms crushing surface inside mouth. •Two V-shaped palatal ridges are found in young turtles; worn smooth in older animals. •Lower rhamphotheca is trough-like with a thick crushing surface. •U-shaped cutting surface is found along the posterior margin. Rhamphotheci Upper RhamphothecaLower Rhamphotheca Rhamphotheci Upper RhamphothecaLower Rhamphotheca•The rhamphotheci are heavily constructed with thick alveolar surfaces. •Both upper and lower jaws come to anterior hook-like points. •Upper rhamphotheca: forms wide crushing surface with sharp-edged alveolar margins. •The palatal portion has large cusps bilaterally. •Lower rhamphotheca is trough-like with two depressions that receive the palatal cusps. •Sharp U-shaped ridge marks the posterior border. Lepidochelys kempii •Rhamphotheci are heavily constructed with thick alveolar surfaces. •Both the upper and lower rhamphotheci are pointed at the anterior midline. •Upper rhamphotheca forms a wide plate with a sharp-edged alveolar surface. •Palatal portion has a ridge bilaterally extending just anterior to the internal choanae. •Lower rhamphotheca has a sharp, wide, V-shaped ridge running posteriorly along the buccal margin. Lepidochelys olivacea


STANDARDMEASUREMENTS The Anatomy of Sea Turtles 28 Standard MeasurementsSeveral different lengths are measured when describing turtle size (Fig. 47). Each measurement is taken in order to ensure that comparative data are available to share with other programs world-wide. Over-the-curve measurements are taken with a non-stretching tape measure while straightline measurements are taken with calipers. The following are the standard measurements and their landmarks. Standard Length (SCL and CCL) are measured from the mid-point of the nuchal scute to the posterior-most tip of the carapace in cheloniids (Figs. 48-49). Standard carapace length is a straightline measurement from the anterior-most point on the midline of the nuchal scute to the posterior-most tip of the last marginal (supracaudal or postcentral) scute. Curved carapace length uses the same landmarks but is taken over the curve of the carapace with a tape measure. If the tape crosses epibionts, notation should be made describing this aberration in the measurement. In leatherbacks, SCL is measured from the middle of the nuchal notch to the posterior-most tip of the caudal peduncle. To measure the CCL of a leatherback, pull the tape tight between the middle of the nuchal notch and the terminal tip of the caudal peduncle, without forcing the tape along the ridge. Fig. 47. Landmarks for standard measurements. Each is described in detail in the text. Fig. 48. Straightline Standard Length: SCL Fig. 49. Over-the-Curve Standard Length: CCL


STANDARDMEASUREMENTS The Anatomy of Sea Turtles 29 Maximum Carapace Length (SCLmax and CCLmax) also sometimes called greatest length, is from the anterior-most part of the carapace to the posterior-most tip of the carapace on the same side (Figs. 52-53). Fig. 52. Maximum Straightline Carapace Length: SCLmax Fig. 53. Maximum Over-the-Curve Carapace Length: CCLmax Fig. 50. Minimum StraightlineCarapace Length (Notch-to-Notch): SCLmin Fig. 51. Minimum Carapace Length Over-theCurve (Notch-to-Notch): CCLmin Minimum Carapace Length (SCLmin and CCLmin) also known as notch-to-notch length, is measured from the mid-point of the nuchal scute to the notch where the two most posterior marginal scutes meet (Figs. 50-51).


STANDARD MEASUREMENTS The Anatomy of Sea Turtles 30 Carapace Width (SCW and CCW) is measured at the widest part of the carapace (not at specific scutes). In leatherbacks, carapace width is at measured the widest points, typically on the most lateral ridges. Care should be taken to ensure that the calipers and/or tape measure are perpendicular to the animal's long axis. The maximum width taken using a tape measure will not always fall on the same location as that measured with calipers (Figs. 54-55). Fig. 54. Straightline Width: SCW Fig. 55. Over-the-Curve Width: CCW Maximum Head Width (HW) is measured using calipers at the widest part of the head (Fig. 56). Fig. 56. Maximum Head Width (HW) is measured at the widest part with the calipers perpendicular to the long axis of the skull. This position varies with species so that, in some, it is near the jaw joint and in others, it is found more posteriorly. Maximum Head Length (HL) is measured along the midline from the anterior-most part of the upper jaw to the posterior-most bone of the skull the supraoccipital crest (Fig. 57). This bone is identified by feeling for the landmark (palpating). Fig. 57. Maximum Head Length (HL) is measured from the posterior tip of the supraocciptal crest (found by palpating) to the anterior-most part of the head, often the rhamphotheca (beak) of the upper jaw.


STANDARD MEASUREMENTS The Anatomy of Sea Turtles 31 Body Depth (BD) is recorded with the animal propped on its side or by digging a trench for the caliper jaws under an adult animal on land. This measurement is taken with calipers at the point of maximum carapace height when the bottom jaw of the calipers is held parallel to the plastron (Fig. 58). Fig. 58. Body Depth (BD) measurements are taken at the body’s maximum height. On a live turtle, an average of at least 3 measurements should be taken between breaths because the depth changes during breathing. Fig. 61. Plastron Length (CPL) ismeasured with an aligned tape measure. This method gives a slightly longer measurement than one obtained with calipers. Plastron Length (SPL), straightline or curved (CPL) is defined by the posterior-most part of the plastron hard structure to its anterior-most hard structure. These points may extend beyond the intergular or gular scute at the ventral base of the neck and the anal or interanal scute of the plastron (Figs. 60-61). Fig. 60. Plastron Length (SPL) is measured with calipers extended from the anterior-most end of the plastron to the posterior-most end. These landmarks may occur beyond the scutes. Fig. 59. Tag tear-out scar on a leatherback. When measuring the animal, be sure to look for tags or tag scars on the front and hind flippers and, in the leatherback, near the tail (Fig. 59).


STANDARD MEASUREMENTS The Anatomy of Sea Turtles 32 Total Tail Length (TTL) is measured from the posterior-most point of the plastron to the tail tip. The Plastron-to-Vent Length (PVTL) a separate measurement, is from the middle of the cloaca, or vent, to the posterior-most tip of the plastron. The Vent-to-Tip (VTTL) measure is taken from the middle of the vent to the tip of the tail or it can be calculated by subtraction (Figs. 62-63). Fig. 63. The Vent-to-Tip measurement (VTTL) shown here, is taken from the middle of the cloaca (vent) to the tip of the tail. Fig. 62. Tail Length (TTL) is typically measured with a tape measure extending from the posteriormost part of the plastron to the tip of the tail. The tape measure is allowed to follow the curl in the tail. Caliper measures tend to be slightly shorter. Fig. 65. Circumference also can be taken with the turtle on its plastron. For very large animals, it may be necessary to dig under the turtle in order to get the tape aligned properly. When the tape is stretched over epibionts, such as barnacles, this should be noted. Fig. 64. Circumference (CIRCUM) is taken with a tape measure. It can be measured with the turtle lying on its carapace. Circumference (CIRCUM) is the greatest circumference taken perpendicular to the turtle's long axis (excluding the flippers; Figs. 64-65).


Methods of DissectionTools and Preparation. Before beginning your dissection, make sure you have all necessary tools, data sheets, pens, and pencils. Tools should include large and small calipers, a tape measure (Fig. 66), a camera, one or more saws, snips (metal or bone shears), one or more sharp knives, scalpel blades and handles, a sharpening stone or steel, and hemostats or pliers (Fig. 67). Other useful tools are blunt probes, forceps with and without teeth, scissors, pipettes and/or syringes for removing fluid. Bowls, plastic bags or jars and string or rubber bands are also useful. Protective gear should minimally include gloves; boots, coveralls or aprons are recommended. Access to towels will be important. Be sure to start with sharp instruments and be prepared to sharpen them frequently. Turtle skin can be tough and dulls knives and scalpel blades quickly. For clean up, herbal and anti-bacterial soaps are good for neutralizing odors and disinfecting, respectively. A 10% chlorine bleach (sodium hypochlorite) solution will help disinfect floors, bowls, or trays. Mix 1 part liquid chlorine bleach with 9 parts water. Check stock solution concentrations; some brands are stronger than others. Bleach solution is too harsh for use on most good tools. METHODS OF DISSECTION The Anatomy of Sea Turtles 33 Fig. 67. Examples of tools used for the dissection (left to right): Metal snips, blunt scissors, pointed scissors, hemostatic forceps, forceps without teeth, blunt probes, and scalpels. A syringe and knife (at the top) are particularly useful. Fig. 66. Tools used to measure the animal: a nonstretching tape measure and large sliding calipers (tree calipers).


METHODS FOR DISSECTION The Anatomy of Sea Turtles 34External examination. A complete description of the carcass should start with an external examination. Species, size, and sex, (if mature) should be noted. Foreign materials, anomalies, and healed or fresh wounds should be described including their locations. Tumors are common in some species, especially green turtles, and should also be described by size, color, texture and location. Starting the dissection. Start by removing the plastron. Make a cut through the skin of the neck then extend it laterally (Fig. 69). Cut around the axillary regions near the plastron and along the seam made by the marginal and inframarginal scutes (Fig. 70). Bony processes from the plastron bones extend into the peripheral bones near the anterior and posterior inframarginal scutes. Hence, the cut cannot follow the seam completely. The skin and muscle near the hind limbs are thin, so care should be taken here to avoid cutting into the body cavity. The cut should follow along the plastron’s posterior margin. When positioning the carcass for dissection, pay attention to proximity to buildings, drainage and tides. Before beginning a dissection, consider the time of day as dissections may take hours. In some cases, packing the animal or some parts of the animal in ice is a good strategy to minimize decomposition. Fig. 69. An outline is shown to trace the path of the initial cut needed to successfully remove the plastron. Instructions for use of this guide. Dissections typically proceed by body region while investigators tend to look-up structures by system. Hence, the dissection will be briefly described by region. The more complete description of each structure, should it be needed, will be found in sections dedicated to the details of organ systems. The following are instructions for the most common dissections. Individuals differ in the order in which they proceed. There is no one correct way, however, all dissections should start with a thorough external examination and verification of the species. Photographs are helpful for verifying species, documenting anomalies, and addressing questions. In most cases, it is easiest to work with a carcass that is placed on its back (Fig. 68). Working with very large animals may require the assistance of heavy equipment to move the carcass. Fig. 68. Carcasses should be placed on their backs for access to most viscera.


METHODS FOR DISSECTION The Anatomy of Sea Turtles 35 Fig. 70. The cut may be made with a knife or scalpel blade. When using a knife, be sure the point is kept very near to the plastron so that it does not cut the viscera. The anterior part of the plastron is attached to the pectoral apparatus (the shoulder bones) via thick connective tissue. (In cheloniids, this is near the midline at the margins where the humeral and gular scutes meet). This connection must be cut close to the plastron (Fig. 71) in both hard-shelled and leatherback sea turtles to avoid damaging the heart, great vessels, or thyroid gland (Figs. 72-73). Once this attachment is free, lift the plastron while separating muscle and blood vessels from the shell by blunt dissection and careful cutting. Blunt dissection, the use of the hands or blunt instruments to separate structures, will often free the shoulder muscles from the plastron and from the peritoneum (the translucent connective tissue covering the organs). Before removing the plastron completely from both sides, locate the greenish gray Rathke's glands in green turtles and ridley turtles. They are located deep to the Rathke's pores (Fig. 22) and embedded in fat. The gland feels denser than the fat when palpated. If a sample is needed, section the gland, and like most organs, if dropped in water, it will sink whereas fat will float, making it possible to distinguish the two. Fig. 71. To free the plastron, the attachment from the acromion processes to the plastron (at arrow) must be cut. Internal Landmarks. Once the plastron is removed, you will see that the ventral surface of the body is mostly covered by muscles (Figs. 72-73). There are 3 major groups of muscles that must be cut or dissected away to expose the viscera. These are the longitudinal muscles along the neck, the large pinnate (feather-shaped) “chest” muscles used for swimming, and the fan-shaped pelvic muscles that were attached to the plastron (Fig. 73). Good landmarks that you can use to find organs are the acromion processes (Fig. 73) and the long triangular coracoid processes (procoracoids; see Skeletal Anatomy, p. 51; Muscle Anatomy, p. 61) on each side of the body. The two acromion processes cross the anterior body just posterior to the neck and extend to the shoulder joint. They attach medially, via ligaments, to the plastron. The coracoid processes extend posteriorly from the shoulder joint toward the abdomen. These two parts of the shoulder girdles serve as attachments for many of the large muscles that move the flippers (Fig. 73; see Skeletal Anatomy Figs. 112-115). The space defined within the borders of the right and left acromion and coracoid process serves as a landmark for the heart, great vessels, and thyroid gland. The major blood vessels will also act as guideposts for locating the thyroid and thymus glands.


METHODS FOR DISSECTION The Anatomy of Sea Turtles 36 Fig. 72. The massive pectoral and pelvic musculature can be seen in this leatherback. The two white patches on the anterior body are the cut ligaments of acromion processes. The head is toward the bottom of the picture. Fig. 73. The ventral pectoral and pelvic musculature covers most of the peritoneum and organs. These must be removed to expose the peritoneal cavity. The paired acromion processes are visible adjacent to the midline but the fanshaped coracoids are covered by the pectoral muscles. Anterior is toward the top of the picture.acromion process pectoral muscles pelvic muscles acromion ligaments


METHODS FOR DISSECTION The Anatomy of Sea Turtles 37Fig. 74. The peritoneum has been removed to expose the layout of the organs. The heart is centrally located, posterior to the trachea. The liver is to each side of the heart. The pectoral girdle was removed from the animal's right side (left in photo) and reflected laterally on the animal's left side. Rotating the acromion and coracoid anteriorly will help separate the muscles from the peritoneum (encasing the viscera). The heart, liver, and major blood vessels (Fig. 74) usually can be seen through this layer. To expose the viscera, remove the flippers and shoulder girdles by breaking the attachments of the scapula to the carapace. Free the shoulder muscles attached to the shell and neck (cut or break them). Twist the acromion and coracoid until the scapula, which extends from the shoulder joint to the anterior carapace, is free. Use blunt dissection to remove the remaining attachments then lift the shoulder girdle and flipper out of the body. Cardiovascular anatomy. Open the pericardium (Fig. 75) to reveal the heart. The pericardial cavity will often contain fluid, particularly in specimens that have been frozen and thawed. Fig. 75. The pericardium contains the heart and pericardial fluid. The great vessels (aortas and pulmonary arteries) are seen posterior to the thyroid, at the fingertip, and the horizontal arteries. The heart is attached posteriorly via the gubernaculum, a cord of tissue at the base of the pericardium. The peritoneum, a translucent fibrous membrane surrounding the organs, is seen to either side of the pericardium. gubernaculum pericardium liver peritoneum


METHODS FOR DISSECTION The Anatomy of Sea Turtles 38Upon opening the pericardium, 3 of the chambers of the heart are visible: the single ventricle, left atrium and right atrium (Fig. 76). The ventricle is attached to the pericardium via a fibrous connective tissue cord called the gubernaculum cordis (Fig. 75). After the gubernaculum is cut, the heart can be rotated anteriorly to reveal the fourth chamber, the sinus venosus The sinus venosus is thin-walled; it collects venous blood from the head, ventricle, lungs and body (see Circulatory Anatomy, Fig. 129). The great vessels (pulmonary artery, left aorta, and right aorta) arise from the anterior and ventral part of the heart. The right aorta gives off a branch almost immediately, the brachiocephalic trunk (Fig. 76) which then branches to the left and right. Small thyroid arteries arise from the brachiocephalic trunk and drain the single thyroid gland. The thyroid gland feels like a round gelatinous mass. Careful trimming of fat and connective tissue will reveal the red to brown thyroid (Fig. 75). The brachiocephalic trunk then forms subclavian arteries laterally, which become axillary arteries as they pass toward the flippers. The right and left thymus glands can be found by following the brachiocephalic trunk to the subclavian and axillary arteries. Feel for the thymus glands along the subclavian and axillary arteries before trying to locate them visually. After you have identified the thymus and thyroid glands, you can remove the heart for detailed examination by cutting through all the vessels and the sinus venosus. You may tie off the vessels before cutting if you want to minimize blood draining into the body cavity. Gastrointestinal Tract and Related Structures. Next examine the gastrointestinal (GI)tract. Expose the esophagus leading to the stomach and the trachea to the lungs with a midventral cut in the neck skin. Open the neck skin and muscle as deep as the hyoid (the skeletal structures that support the tongue and some neck muscles). Cut along the inner surface of the lower jaw to free the tongue, glottis, trachea, and esophagus. The trachea and esophagus will exit posterior to the hyoid apparatus. The esophagus is deep and slightly to the (turtle's) right of the trachea. Cartilaginous rings characterize the trachea. The esophagus is a collapsed muscular tube. If you have difficulty finding the esophagus, you can run a blunt instrument or tube down the throat and locate the structure by moving your probe. In the body cavity, the esophagus makes a sharp curve to the left to join to the stomach. The stomach leads to the small intestine with its digestive glands (liver and pancreas). The large intestine joins the distal small intestine and the GI tract ends with the rectum (Fig. 77). Fig. 76. The heart has 4 chambers: the sinus venosus, right atrium, left atrium, and ventricle. The two aortas and pulmonary trunk emerge from the anterior aspect of the ventricle and are seen between the two atria. The brachiocephalic trunk is a landmark for locating the thyroid and thymus glands. The heart is pushed laterally to show the sinus venosus. right atrium left atrium brachiocephalic trunk sinus venosus ventricle


METHODS FOR DISSECTION The Anatomy of Sea Turtles 39 Figs. 77a and 77b. The gut of a hawksbill after it has been removed and cut free from the liver, spleen, mesenteries, and cloaca. The GI tract includes the esophagus, stomach, small intestine, and large intestine, which are easily distinguished from one another. Once you have located the esophagus, tie it off near the mouth with string or rubber bands that will not slip. You can then cut it away from the mouth and start removing the gut for examination. Separate the esophagus and stomach from the trachea and liver by blunt dissection. The stomach is attached to the liver's left lobe ventrally and to the left lung dorsally. These attachments must be cut or broken carefully in order to free the stomach and leave the liver and left lung intact. Continue to remove the gut by tearing or breaking the mesenteries (flat tissues that suspend and support the organs) and blood vessels. Be careful not to cut the stomach or intestines. The stomach joins the small intestine at the pyloric sphincter a thick muscular sphincter or valve. Just past the pyloric sphincter, the pancreas can be seen running distally along the duodenum (Fig. 77) past the common bile duct (a short attachment to the gallbladder which is found in the liver's right lobe). The pancreas is usually smooth, shiny (pink to peach colored), except in turtles that have decomposed. The common bile duct from the gallbladder can be identified by the green bile stain. The spleen can be found near the distal end of the pancreas. It is nearly round to oblong in shape, dark red, and highly vascular (see Circulatory Anatomy, Fig. 158 and Gastrointestinal Anatomy Fig. 164). The intestine is long and must be cut away from its highly vascular, fan-shaped mesentery. The posterior part of the intestine is the colon (large intestine), which ends in a muscular rectum (Fig. 77). The a brectum caecum ileum and jejunum large intestine duodenum and pancreas stomach esophagus


METHODS FOR DISSECTION The Anatomy of Sea Turtles 40 Figs. 78a and 78b. The lungs are in contact with the carapace. By tracing the trachea posteriorly to the 2 bronchi, the lungs can be found. They extend for most of the length of the carapace. The gonads are found at the base of each lung. In this animal, the testes are shown. left aorta trachea primary bronchi right aorta right lung colon cut kidney testis left lung rectum is often pigmented. It enters the cloaca a chamber that receives urine, eggs or sperm. Before cutting through the rectum, tie itoff with string or rubber bands. The urinary bladder (discussed shortly) is anatomically ventral to the rectum and is suspended on the midline of the pelvis.It too, connects to the cloaca. Before opening the gut to examine the contents and the lining, it helps to tie it off in 3 or more sections so that there are landmarks available when describing the parts. By using pairs of ties, the gut can be cut without spilling the contents. The gross appearance of the lining of the intestines does not always allow one to describe the location of a structure, tissue, or contents, so preset landmarks are useful. When opening the intestine, it helps to have trays or bowls ready to receive contents. If you have not removed the liver with the gut, do so now by carefully freeing it from its attachments to the lungs and the peritoneum. The dense liver is composed of two lobes, with a connection of varying size between the two (Fig. 73). The right lobe is usually larger and, on its posterior surface, houses the round gallbladder. The gallbladder is usually dark green and may be full and convex or collapsed and concave (when empty). Once the gut is removed, it is easy to see the lungs and the gonads (Fig. 77) at their posterior margin. a b


METHODS FOR DISSECTION The Anatomy of Sea Turtles 41Gonads. The gonads are attached to the peritoneal wall, posterior to the lung and anatomically ventral to the kidneys. The ovaries of mature and maturing turtles have a number of round yellow follicles that appear as small (~2 mm 2 cm) diameter spheres embedded throughout the length of the long narrow organ. Immature ovaries are more compact, flat, often elongate, and fusiform in outline. They are often pink and granular in appearance. Ovaries tend to be attached along their length by one edge. The oviduct transports the follicles, then eggs, to the cloaca when mature. The oviduct is located lateral to the ovary and is not attached to it. Each oviduct extends anteriorly from the cloaca for about 2/3 the length of the body. In mature turtles, it has an "accordion" appearance. In immature turtles, it is a simple flat tube that is very narrow in the youngest and increasingly wide in older turtles (see Urogenital Anatomy, Figs. 220-221). The testis is often yellow or tan, and smooth. It is fusiform in outline and is attached to the body wall by its flat dorsal surface. The vas deferens is a coiled tube that is found lateral to the testis transports sperm to the cloaca. In breeding males, both the testis and the vas deferens become enlarged. When in doubt about the sex of the turtle, the coiled vas deferens, even in young turtles, is an important clue (see Urogenital Anatomy, Figs. 221-222). Lungs. The lungs are located dorsally and are attached to the carapace and vertebral column (Fig. 78). In some species (e.g., Lepidochelys kempii and Caretta caretta ) the lungs are more closely attached to the vertebral column than in other species. The lungs can either be examined in the body, or by removing them. To remove the lungs, free their lateral borders, being careful not to cut into the lung tissue. The medial border of the lung will be firmly attached to each side of the vertebral column. Sometimes it helps to free the trachea from the associated connective tissue prior to breaking the fibrous connections between the lung and the vertebrae. The trachea bifurcates into two bronchi. A bronchus enters each lung and continues with multiple internal openings into the lung. Each bronchus extends almost to the posterior end. The lungs are spongy and highly elastic. Urinary bladder and kidneys. The urinary bladder is suspended from the midline on the dorsal surface of the pelvis (Fig. 79). It is located between the rectum and the anterior pelvis (pubis). The bladder opens into the cloaca and is not connected to the kidneys. Urine flows from the kidneys, through the ureters to the cloaca. Urine enters the bladder from the cloaca (see Urogenital Anatomy, Fig. 219). The kidneys are located posterior to the lungs. They are "retroperitoneal" which means that they lie beneath the peritoneal lining next to the carapace. Fig. 79. A kidney in this young leatherback, is exposed and its circulation injected to separate arteries from veins. The urinary bladder is seen on the midline, as is the collapsed large intestine to one side. The dorsal aorta is along the vertebral column and gives off many branches. dorsal aorta large intestine kidney urinary bladder


METHODS FOR DISSECTION The Anatomy of Sea Turtles 42They are deep relative to the gonads and slightly medial from the posterior-most border of the lungs. By making a cut in the peritoneum and teasing it away, the lobular red kidneys (Fig. 79) and their extensive systems of arteries and veins can be exposed. The ureters, often difficult to find, extend from each kidney to the cloaca. At the anterior end of each kidney, and very near the vertebral column, there is a small elongate adrenal gland The adrenal glands are often yellow or orange. They are frequently easier to locate by palpation than by sight (see Glands, Fig. 186). Brain. To examine the brain, cut off the head near the base of the skull. Secure it with a vice or hold it carefully on a no-skid surface. In Dermochelys coriacea the brain and its tracts make a series of dorsoventral turns as it proceeds from anterior to posterior. A single cut will not expose this well protected structure. In the cheloniids, one of the easiest ways to expose the brain, in the absence of special saws, is to make a straight cut from the top of the snout, proceed along the inside of the top of the orbits, then continue to the posterior end of the head (Fig. 80). Once the skull cap is removed, the small brain can be seen (Fig. 81) with its (anterior to posterior) olfactory tracts to the nose, optic lobes, cerebral hemispheres and cerebellum (see Nervous System, Figs. 187 and 189). Sometimes the fibrous covering, the dura mater, remains covering the brain. This can be cut away. Fig. 80. The brain can be exposed by a cut parallel to the skull’s long axis, running from the snout, through the tops of the orbits and posteriorly toward the middle of the supraocciptal crest. Fig. 81. The brain, along the midline, is elongate and white. Grossly, one can see the olfactory tracts. The olfactory bulbs, cerebral hemispheres, and optic lobes are covered by the dura mater; the cerebellum is the single round structure at the end of the exposed brain. If the brain is removed, then lateral and ventral cranial nerves and the pituitary can be seen. The two round, lobed structures dorsal and posterior to the eyes are the salt glands. The remaining dark tissue is muscle.brain salt gland


SKELETAL ANATOMY The Anatomy of Sea Turtles 43 Skeletal AnatomyThe skeleton is composed of bones and cartilages. Typically, it is divided into 3 main parts: the skull, axial skeleton and appendicular skeleton (Figs. 8284). In sea turtles, each of these bony groups is a composite of several structures. The skull includes the braincase, jaws, and hyoid apparatus (Figs. 85-86). The axial skeleton is composed of the carapace, vertebrae, and ribs and the derivatives of the ribs. The plastron (Fig. 83) is a composite including derivatives of the axial and appendicular skeleton (ventral ribs plus shoulder elements). The appendicular skeleton includes the flippers,hind limbs and their supporting structures (the pectoral and pelvic girdles ). Fig. 82. This CT (computed tomography) scan of an immature ridley turtle shows the three parts of the skeleton: the skull, axial, and appendicular skeletons and the spatial relationships of the bones. Cartilage (at the ends of many bones) is not detected by this imaging technique so bones appear loosely articulated. The arrangement of the for elimbs is such that the shoulder joint is inside the shell. The elbow flexes so the forearm moves from an anterolateral position to a medial position. Lines crossing the posterior skull and carapace are image processing artifacts. Fig. 84. In this lateral view of an immature loggerhead, the hyoid process can be seen clearly as it passes posterior and ventral to the skull. Note that the orbits contain a ring of bones (scleral ossicles) that support the eyes. The right hind limb is directed laterally so it cannot be seen clearly. Fig. 83. Individual plastron bones are not fused in immature turtles. The processes from the lateral plastron do not yet articulate with the peripheral bones. The hyoid apparatus (the body of the hyoid and both bony hyoid processes), which is usually lost in skeletal preparations, can be seen in the throat region. The distal phalanges of the flippers were outside of the field of view in this CT scan so the ends of the flippers are omitted.


SKELETAL ANATOMY The Anatomy of Sea Turtles 44Figs. 85a and 85b. Loggerhead skull (ventral) showing parts of the ceratohyal or the body of the hyoid, and paired hyoid processes of the hyoid apparatus. Two cartilaginous hyoid processes are lost in skull preparation. Hyoid bones are loose in the prepared skull but are suspended between and behind the lower jaws in life. The hyoid apparatus supports the tongue and glottis and serves as muscle attachment sites for some of the throat muscles. Part of the atlas (ventral cervical vertebra 1) is resting on the occipital part of the skull, posterior to the hyoid apparatus. Fig. 86. Hyoid apparatus. The hyoid body supports the glottis in its concavity. Muscles attach to the hyoid processes (ceratobranchial bones) that move the throat. Cartilaginous processes are missing. ceratohyal bone ceratobranchial bone ab dentary bone ventral cervical vertebra 1


SKELETAL ANATOMY The Anatomy of Sea Turtles 45Figs. 87a and 87b. Lateral view of the cervical vertebrae from an adult green turtle. Each vertebra is composed of a ventral body and a dorsal arch. The ventral part of the atlas is missing from this series. The atlas articulates with the occipital condyle at the back of the skull. C7 articulates with the cervical vertebra fused to the carapace. Fig. 88. The atlas (C1) and axis (C2) complex and C3 C4, in lateral view. Dorsal is to the right. The vertebral arches of the successive cervical vertebrae articulate via sliding joints (arrows) that allow some dorsalventral bending of the neck, but little twisting. Each vertebra is composed of separate dorsal and ventral elements. atlas axis C4 C5 C6 C7 C3C2 C3 C4 b a Like all turtles, sea turtles have 7 mobile cervical vertebrae (an 8th is fused to the carapace; Figs. 8788) and 10 thoracic vertebrae. There are 2-3 sacral vertebrae and 12 or more caudal vertebrae (Figs. 89-90). The caudal vertebrae of females are short and decrease in size distally; those of mature males are large with robust lateral and dorsal processes (Fig. 89). Each thoracic vertebra articulates with a pair of ribs, bilaterally arranged. Each rib head is aligned with the junction of two vertebral bodies (Fig. 91). Fusions of vertebrae and ribs with dermal bone result in unique carapacial bones. Neural bones are associated with the vertebral column, pleurals are formed by the ribs and their dermal expansions, and peripheral bones form the margin of the carapace (Figs. 92-93). The anterior-most bone is the nuchal and the posterior-most is the pygal Between the last neural bone and the pygal is the suprapygal ,which lacks any vertebral fusion (Figs. 92-93). The lateral processes of the sacral vertebrae are not fused to the carapace (Fig. 89). vertebral body of atlas


The Anatomy of Sea Turtles 46 SKELETAL ANATOMY S1 S2 S3 caudal vertebraeFigs. 89a and 89b. The sacral and caudal vertebrae of an adult male green turtle. The large dorsal and lateral processes are the sites of attachments for the muscles that move the prehensile tail of mature males. S: sacral The lateral extensions of the sacral vertebrae are formed by rib-like processes that articulate with the ilium. Fig. 90. Cleared and stained hatchling loggerheads. (Left) Dorsal view with carapace removed showing vertebral regions and the level of ossification at the time of hatching. (Right) Dorsal view showing ribs, vertebrae and initial dermal bone hypertrophy along the ribs as the carapace develops. The plastron was removed in this specimen. b a In hatchlings and Dermochelys the carapace is composed of ribs and vertebrae. In cheloniids, as they mature, the shell becomes increasingly ossified. Dermal bone hypertrophies between the ribs and grows outward to form the carapace (Figs. 90 and 92-93). The ribs grow laterally to meet the peripheral bones (lying beneath the marginal scutes) in Caretta caretta Eretmochelys imbricata and Chelonia mydas In Lepidochelys kempii the peripheral bones also widen with age and increasing size. The spaces between the ribs and the carapace, fontanelles are closed by a membrane underlying the scutes. The fontanelles are closed completely by bone in some adult ridleys and loggerheads, but are retained posterolaterally in green turtles and hawksbills (Fig. 93).


SKELETAL ANATOMY collapsed spinal cord rib head vertebral body rib Figs. 91a and 91b. Ventral view of the carapace showing the arrangement of the ribs and vertebral bodies. The vertebral arch is incorporated into the vertebral (neural) bones of the carapace and hence, is not seen in this view. The spinal cord travels in the space formed between the neural bones and the vertebral bodies. b a The Anatomy of Sea Turtles 47


Figs. 93a and 93b. Ventral view of this hawksbill carapace shows the vertebral bodies (dorsal elements), ribs, and fontanelles. The ribs have fused with the peripheral bones anteriorly. D: dorsal elements. a Figs. 92a and 92b. The bones of the carapace dorsal view are identified in this Kemp’s ridley. The bony arrangement of the shell is such that in some species supernumerary neural bones are common. nuchal neural bones pleural bones peripheral bones suprapygal pygal b a attachment to cervical vertebra 8 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 ribs fontanelles b SKELETAL ANATOMY The Anatomy of Sea Turtles 48


The Anatomy of Sea Turtles 49 SKELETAL ANATOMY The carapace is composed of bone covered by keratinous scutes (cheloniids, Fig. 94) or blubber and skin in Dermochelys (Fig. 95). The margins of cheloniid scutes and the bones' sutures do not align with one another (Fig. 96). In the leatherback, the blubber overlies ribs and vertebrae and itself is covered dorsally with waxy skin and embedded dermal ossicles (Fig. 95). nuchal marginal scutes lateral (costal scutes) supracaudal scutes vertebral scutes Figs. 94a and 94b. The scutes are keratinous epidermal structures that grow above the carapace bones. Scutes grow two ways. They increase in size (area) at their margins. The entire scute can increase in thickness. Fig 95. Dermal ossicles are bony plates that reside deep to the skin in the leatherback carapace. ab


SKELETAL ANATOMY The Anatomy of Sea Turtles 50The plastron is composed of 4 pairs of bones in sea turtles (from anterior to posterior: epiplastron, hyoplastron, hypoplastron and xiphiplastron ) and 1 unpaired bone ( entoplastron ; Fig. 97). The shape of the entoplastron bone is sometimes used as a key characteristic (Fig. 98) for species identification. Fig. 96. Immature loggerhead skeleton showing outgrowth of dermal bone to form the shell. The spaces between the ribs and the peripheral bones are the fontanelles. The pattern of the scutes is barely visible but hints at the lack of alignment with bony sutures. The distal parts of the flippers are cut off by the field of view in this CT image. Figs. 97a and 97b. The plastron is composed of 9 bones that are separate in hatchlings but become fused in older turtles. Anterior is toward the top of the picture. epiplastron entoplastron hyoplastron hypoplastron xiphiplastron b a


SKELETAL ANATOMY The Anatomy of Sea Turtles 51 Eretmochelys imbricata Chelonia mydas Lepidochelys kempii Caretta carettaFig. 98. The distinct shape of the entoplastron bones may serve as a key characteristic to distinguish some cheloniid species. In E. imbricata and C. mydas the elongated shaft is narrow. The bone is roughly Tshaped in hawksbills and the shaft narrows abruptly. It is arrow-shaped in green turtles; wide anteriorly with a shaft that narrows gradually. In L. kempii and C. caretta, the shaft is wide. The overall shape isalmost dagger-like in the Kemp's ridley as the shaft narrows gradually. The bone is cruciform in loggerheads; the lateral processes are distinct and the shaft tapers along its posterior half. The entoplastron has not been described diagnostically for the olive ridley. Entoplastron bones change shape during ontogeny, hence it is recommended that this characteristic be used only in adults. In Dermochelys there is no hypertrophy of bone between the ribs of the carapace. The bony carapace remains composed solely of an expanded nuchal, ribs, and vertebrae. Ventrally, the plastron is composed of aring of reduced plastron bones. No entoplastron is present. The anterior appendicular skeleton includes the flippers and pectoral girdles. The pectoral girdles are composed of two bones, the scapula with its acromion process and the coracoid (= procoracoid); these form a triradiate structure (Fig. 99). Fig. 99. The pectoral girdle, (left to right) in ventral, posterior, and anterior views, is composed of two bones and 3 parts that serve as a major site for attachment of the swimming musculature. The acromion process extends medially from the ventral part of the scapula. The coracoid a ventral bone, is flat and wide distally. The shoulder joint (glenoid fossa), is formed by the coracoid and the scapula. (After Wyneken, 1988). glenoid fossa coracoid acromion process acromion process scapula glenoid fossa coracoid


SKELETAL ANATOMY The Anatomy of Sea Turtles 52Fig. 100. Skeletons of flippers (left and right) shown in dorsal view. Note the flat wide wrist and the elongated digits that form the flipper blade. claw radiale intermedium radius pisiform centrale phalanges metacarpal distal carpals ulna ulnare I II III IV V The scapula is aligned dorsoventrally and attaches to the carapace near the first thoracic vertebra. Ventrolaterally it forms part of the shoulder joint, the glenoid fossa (Fig. 99). The acromion processes extend medially from each scapula to articulate with the entoplastron via ligaments. The coracoids form the remainder of the glenoid fossa and then extend posterior medially. Each terminates in a crescentshaped coracoid cartilage. The acromialcoracoid ligament extends from the acromion to the coracoid. The majority of the flipper retractor and abductor muscles attach to the coracoid processes and the acromialcoracoid ligaments. The forelimb is composed of the humerus radius and ulna, carpals, metacarpals, and 5 phalanges (Figs. 100-103). The flipper blade is formed by widening and flattening of the wrist bones and elongation of the digits (Fig. 100). The humerus, which articulates with the shoulder at the glenoid fossa, is flattened with its head offset by ~20 from the bone's shaft (Fig. 101). There is a large bony medial process extending beyond the humeral head to which flipper abductor and extensor muscles attach (Fig. 101). Distal to the head and almost diagonally opposite is the lateral process or deltoid crest to which attach flipper protractor muscles (Figs. 101-103). In Dermochelys, the humerus is extremely flattened. It is composed primarily of cancellous bone, relatively little cortical lamellar bone, and with thick vascular cartilage on its articular surfaces (Figs. 104-105). In prepared skeletons, the cartilage is often lost. The extensive vascular channels in the cartilage are indicative of chondro-osseus bone formation (Fig. 104). This is unlike the cheloniid bone, which is formed by deposition of relatively thick layers (lamellae) of cortical bone around a cellular bony core (cancellous bone; Fig. 105). The flipper (Fig. 100) is composed of wrist elements ( radiale, ulnare, centrale, pisiform, distal carpals ) and elongated metacarpals and phalanges (Figs. 100, 102-103). The radius and ulna are short in sea turtles and, in adults, functionally fused by fibrous connective tissue.


SKELETAL ANATOMY The Anatomy of Sea Turtles 53 intermedium centrale humerus lateral process distal carpals radius ulna pisiform medial ulnare metacarpal I V IV II III Figs. 102a and 102b. Dorsal view of a leatherback flipper. b a Fig. 101. The cheloniid humerus is distinctive in its form with a slightly offset head and enlarged medial process. Almost opposite the medial process and just distal to the head is a U-shaped lateral process (deltoid crest) to which attaches the major ventral swimming muscles. (After Wyneken, 1988). head deltoid crest ulnar condyle radial condyle medial process


SKELETAL ANATOMY The Anatomy of Sea Turtles 54 intermedium humerus medial process centrale radius ulna pisiform distal carpals ulnare metacarpal I V IV II III Figs. 103a and 103b. Ventral view of the leatherback flipper. The articulated forelimbs of this leatherback shows some of the extensive cartilages at the bone ends and the extreme elongation of the digits. The large humerus has an almost primitive form with its flattened profile and extended medial process. The head and distal articulations to the radius and ulna are largely cartilaginous. b a The pelvis is composed of 3 pairs of bones; pubis, ischium, and ilium The pubic bones and the ischia form the ventrally positioned part of the pelvis (Fig. 106). The two ilia are oriented dorsoventrally, articulate with the sacral vertebrae, and attach the pelvis to the carapace via ligaments. All 3 bones form the acetabulum (hip socket) on each side. They are separate bones joined by cartilage in hatchlings but quickly ossify and fuse to form a single structure in older turtles. The pelvic bones of the leatherback, however, remain connected by cartilage throughout life (Fig. 107) and become separate elements when skeletons are prepared.


SKELETAL ANATOMY The Anatomy of Sea Turtles 55 Figs. 106a and 106b. This loggerhead pelvis, dorsal view, shows the 3 bones fused (pubis, ischium, and ilium) that form each side. The epipubic cartilages that would form the anterior edge of the pelvis in life are missing from this preparation. The ilia articulate with the sacral vertebrae and carapace. Anterior is toward the bottom of the picture. Fig. 104. Chondro-osseus bone formation. Vascular channels are seen in this cut end of a leatherback humerus. Fig. 105. Longitudinal sections through humerii. The loggerhead humerus (top) has relatively more lamellar bone (light color) than in the leatherback humerus (bottom). The lamellar bone is deposited in layers in some cheloniid species and populations; in others, layers are not distinct. a ischium lateral pubic process pubis thyroid fenestra pelvic symphysis ilium acetabulum b


SKELETAL ANATOMY The Anatomy of Sea Turtles 56The hind limb articulates with the pelvis via the head of the femur which fits in the acetabulum. The femur has a relatively straight shaft with a strongly offset head. There are major and minor trochanters distal to the head (Fig. 108); these are attachments for most of the thigh retractors and adductors, respectively. The distal femur articulates with the tibia and fibula. The short ankle consists of the calcaneum, astragalus, and distal tarsals There are five digits. The 1st and 5th metatarsals are wide and flat and the phalanges are extended adding breadth to the distal hind limb area (Figs. 109 110). femoral head minor trochanter minor trochanter major trochanter major trochanter tibial condyle tibial condyle tibial condyle fibular condyle fibular condyle fibular condyle Fig. 108. Left and right femurs anterior view (left) immature turtle, posterior view (right) mature turtle. The femur, an hour glass-shaped bone, has an offset head. The trochanters become more pronounced as the turtles age. Figs. 107a and 107b. The pelvis of the leatherback is composed of both bone and cartilage throughout life. Hence, skeletal preparations of the pelvis usually result in 3 pairs of bones which do not retain their spatial relationships. Anterior is toward the top of the picture. pubis ilium ischium b a


SKELETAL ANATOMY The Anatomy of Sea Turtles 57 Figs. 109a and 109b. Dorsal view of a leatherback hind limb. The articulated hind limb shows the extensive cartilages between bones that are typical of the leatherback skeleton. The hind foot is wide and the digits somewhat elongated. Digits are designated by numbers, with I being the digit on the tibial side and V on the fibular side. a calcaneum fibula tibia astragalus tarsals metatarsal femur I V IV II III b


SKELETAL ANATOMY The Anatomy of Sea Turtles 58 Figs. 110a and 110b. Ventral view of the leatherback hind limb. The femur is the bony element of the thigh, the tibia and fibula are the bony elements of the shank. The ends of these bones are cartilaginous. The ankle is somewhat flattened and laterally expanded, resulting in wide placement of the digits. This architecture contributes to the rudder-shape of the hind limb. a femur calcaneum fibula tibia astragalus tarsal metatarsal I V IV II III b


MUSCLE ANATOMY The Anatomy of Sea Turtles 59 Muscle AnatomyThe muscles are responsible for moving structures, modifying the function of other muscles, and stabilizing joints. Muscles originate and insert via tendons. The origin of a muscle is its fixed point while the insertion is typically the point that it moves. Muscles can attach via their tendons to bones, muscles, skin or eyes. Where known, the innervations of the muscles are reported. For reading ease, the designation of M ., prior to muscles names, has been omitted. Names and key concepts are given in bold the first time the muscle is discussed. Muscle functions are described with each figure. As they apply to sea turtles, these functions are as follows. Flexion bends one part relative to another at a joint; extension straightens those parts. Protraction moves one part (usually a limb) out and forward; retraction moves that part in and back. Abduction moves a part away from the ventral surface; adduction brings the part toward the body's ventral surface. Rotation turns a structure. Depressor muscles open (a special form of abduction) a structure, jaws in this case, while levators close jaws (a kind of adduction). Muscle groups. The muscles described here are the major or large muscles (detailed discussion of most muscles can be found in the primary literature). For convenience, muscles are grouped by region; axial muscles, include the head muscles; ventral muscles include both proximal pectoral and pelvic muscles that are associated with the plastron; forelimb and respiratory muscles are those found on the flippers, carapace, and scapula involved in flipper movements and breathing. Posterior muscles are the large muscles of the hip, thigh, and lower leg. Muscles of the flipper blade and hind foot are not discussed or illustrated in detail here because they are obscured by extensive connective tissue and are difficult for most to identify, even with special dissection equipment and techniques. Ventral Muscles. The massive ventral musculature is found after removing the plastron (Fig. 111). This musculature is dominated by a superficial muscle, the pectoralis major which originates on the plastron and inserts on the lateral process and shaft of the humerus. Anterior to the pectoralis and ventral to the acromion processes are two muscles: the deltoideus (ventral part), which originates on the ventral scapula, acromion, and anterior plastron bones and the supracoracoideus, which has several subdivisions. Its anterior part originates on the acromion (Figs. 112-1 14). Both the deltoideus and the anterior part of the supracoracoideus insert on the lateral process of the humerus. These 3 ventral muscles function in swimming and respiration (by movement of the shoulders and plastron). Their innervations are via the supracoracoid nerve from the ventral portion of the brachial plexus (see Nervous System, Figs. 204-206). After removing the pectoralis major, deep locomotor muscles are found associated with the pectoral girdle (Figs. 112-114). The biceps brachii has several subdivisions, or heads, in sea turtles. The superficial head (Figs. 112-114) originates on the coracoid and extends via a long tendon to insert on the radius and ulna; the profundus head inserts on the humerus and radius.Innervation is via the inferior brachial flexor and median nerves. The coracobrachialis magnus originates on the dorsal side of coracoid process and inserts on the medial process of the humerus. The posterior part of the supracoracoideus (Fig. 112) originates on the coracoid and its cartilage and inserts in the lateral process of the humerus. These muscles are innervated by the supracoracoid nerve. There is an extensive series of arteries and veins running within and between these very active muscles (Fig. 114). A pair of superficial posterior muscles, the left and right rectus abdominis (Fig. 111) are found ventrally. Each originates on the lateral pubis and inserts on the plastron. They stabilize the pelvis and may function in compressing the plastron during breathing.


The Anatomy of Sea Turtles 60 MUSCLE ANATOMY supracoracoideus deltoideus pectoralis major rectus abdominus a b Figs. 111a and 111b. Superficial ventral muscles of the pectoral and pelvic girdles. The large pectoralis major is a forelimb retractor and adductor. Both the deltoideus and the supracoracoideus protract and abduct the humerus. The rectus abdominus is a pelvic stabilizer. Anterior is toward the top of the picture.


MUSCLE ANATOMY a Figs. 112a and 112b. The deep pectoral muscles are exposed after removal of the pectoralis major. These forelimb retractors, separated on the animal's left (right in picture), are the biceps brachii superficialis and coracobrachialis magnus. The posterior part of the supracoracoideus both adducts and retracts the flipper. deltoideus head acromion process coracobrachialis magnus coracoid process supra coracoideus(posterior part)pectoralis major(cut away medially) biceps brachii superficialis acromial coracoid ligament supra coracoideus(anterior part)b The Anatomy of Sea Turtles 61


MUSCLE ANATOMY The Anatomy of Sea Turtles 62Fig. 113. Diagrams of cheloniid right shoulder muscles including locomotor and respiratory muscles. Superficial ventral muscles (top left), deep ventral muscles (bottom left), posterior muscles (bottom right), and lateral muscles (top right). The extensor digitorum, extensor radialis intermedius, tractor radii, and flexor carpi all control the extension and flexion of the flipper blade. Ext.= extensor, h.= head, Inf.= inferior, Interm.= intermedialis. (After Wyneken, 1988) brachialis inf. tractor radii triceps scapular h. deltoideus ventral part acromion pectoralis major ext. radialis interm. triceps humeral h. ext. digitorum acromialcoracoid ligament supracoracoideus anterior part triceps humeral h. carapace testoscapularis(cut)testocoracoideus subscapularis latissimus dorsi teres major triceps scapular h. flexor carpi ulnaris biceps superficialis biceps profundus tractor radii extensor digitorum ext. radialis interm. biceps profundus biceps superficialis acromialcoracoid ligament brachialis inf. triceps humeral h. triceps scapular h. coracoid cartilage deltoideus supracoracoideus anterior part supracoracoideus posterior part testoscapularis(cut)subscapularis latissimus dorsi teres major triceps humeral h. extensor radialis interm. extensor digitorum brevis coracobrachialis biceps profundus biceps superficialis triceps scapular h. flexor carpi ulnaris testocoracoideus coracobrachialis


MUSCLE ANATOMY The Anatomy of Sea Turtles 63 a Figs. 114a and 114b. The deep pectoral muscles of the animal's right side are shown in detail. The supracoracoideus has two parts: posterior, which protracts and anterior, which retracts the forelimb. pericardium coracoid processb cut acromial coracoid ligament pectoral arteries and veins biceps superficialis supracoracoideus(anterior part) supracoracoideus(posterior part)acromion process


MUSCLE ANATOMY The Anatomy of Sea Turtles 64Forelimb and Respiratory Muscles. The latissimus dorsi/teres major complex the scapular head of the deltoideus and the subscapularis originate on the carapace and/or shoulder girdle and insert on the proximal humerus (Fig. 113). The latissimus dorsi and teres major together originate on the scapula and the carapace from the attachment point of the scapula, along the first pleural bone to the anterior peripheral bones. They insert via a common tendon just distal to the head of the humerus. The scapular head of the deltoideus arises from the anterior scapula and inserts on the lateral process and shaft of the humerus. The subscapularis muscle is very large, originates on the medial and posterior scapula, and inserts on the large medial process and the shaft of the humerus. These muscles are innervated by the deltoid nerve (a branch of the brachial plexus). There are two sheet-like respiratory muscles located dorsally, which are often destroyed when removing the pectoral girdles (Figs. 113 and 115). These are the testocoracoideus (origin: carapace near the anterior inframarginals; insertion: dorsal coracoid) and testoscapularis (origin: carapace posterior to the latissimus dorsi; insertion: dorsal scapula and the scapular attachment to the carapace). They are innervated by cervical spinal nerves. The remaining dorsal shoulder muscle, the triceps brachii (= triceps superficialis) has two heads in cheloniid sea turtles (Figs. 113-116). The humeral head arises from the humerus, and the scapular head arises from the scapula. Both converge to form a common tendon inserting on the proximal ulna. This muscle may have only a humeral head in Dermochelys The triceps is innervated by the superficial radial nerve (a branch from the superior brachial nerve of the brachial plexus). Fig. 115. Ventral pectoral muscles with arteries and veins. The pectoral artery is found running along the deep muscles of the shoulder. The testoscapularis, a respiratory muscle, is deep to the pectoralis. Other pectoral muscles originating on the coracoid are reflected medially (to the right) in this picture. testoscapularis muscle


MUSCLE ANATOMY The Anatomy of Sea Turtles 65 Fig. 116. Superficial dorsal forelimb muscles (right). The two heads of the triceps brachii, (triceps scapular head and triceps humeral head) are forelimb adductors, which twist the flipper. The more medial biceps and flexor carpi ulnaris muscles flex the flipper blade. The extensor digitorum muscle becomes diffuse in adults as fibrous connective tissue stiffens the flipper blade. Young turtles can extend the digits, somewhat mature turtles cannot. Fig. 117. Ventral forelimb muscles (right). Most of the ventral muscles flex the flipper blade relative to the upper arm. The extensor radialis extends the flipper. The scapular head of the triceps may twist the flipper blade along its axis, or abduct the forearm. Fig. 118. Dorsal forelimb muscles of an immature hawksbill. In young animals, the muscle divisions of the forearm and the flipper, particularly, are more obvious than in older animals. Less connective tissue is present and the digits can flex and extend to a limited extent.triceps scapular head extensor digitorum extensor radialis intermedias brachialis inferior tractor radii tendon triceps scapular head triceps numeral head flexor carpi ulnaris triceps humeral head biceps superficialis and profundus biceps profundus triceps scapular head extensor carpi ulnus flexor carpi ulnaris I II III IV V IV triceps humeral head extensor digitorum brevis & longus biceps superficialis


MUSCLE ANATOMY latissimus dorsi scapula cervical vertebra(cut)head triceps brachii scapular head triceps brachii humeral head teres major muscle subscapularis muscle coracobrachialis magnus muscle latissimus dorsi(cut) Figs. 119a and 119b. Dorsal view of the pectoral musculature. The carapace, skin and fat have been removed (from left). The head, cut cervical vertebra, and scapular ends provide landmarks for orientation. The latissimus dorsi, a large sheet-like muscle, is shown intact (animal's right) and cut (animal's left). It, plus the teres major and deltoideus (scapular head, not shown), abduct and sometimes protract the flipper. The large subscapularis is a strong flipper protractor. The coracobrachialis, a ventral muscle, is seen extending from the shoulder posteriorly, toward its origin, the coracoid. a b The Anatomy of Sea Turtles 66


The Anatomy of Sea Turtles 67 MUSCLE ANATOMY The biceps muscle may have one or two parts (Figs. 112 and 114). When two heads are present, the biceps superficialis arises from the coracoid and inserts on the pisiform of the wrist. The muscle has two bellies in series, with a short tendon in the middle. The second and most prominent head, the biceps profundus also originates on the posterior coracoid, but ventral to the biceps superficialis and inserts via a tendon with the brachialis on the ulna (Fig. 114). In Dermochelys and Lepidochelys often there is just a single head inserting on the radius and ulna. left flipper carpal extensors coracobrachialis muscle biceps profundus biceps superficialis(cut)distal humerus teres major subscapularis latissimus dorsi(cut)triceps brachii(cut)scapula Figs. 120a and 120b. The pectoral muscles of the left shoulder, arm and flipper. The large subscapularis covers most of the scapula. The large coracobrachialis is seen ventrally, covering much of the coracoid. The biceps muscle has one or two heads (varying among species and among individuals). The biceps superficialis extends from the shoulder (mostly the coracoid) to the pisiform bone of the wrist, and probably helps control the twist or rotation of the flipper blade. The biceps profundus (seen only as a partial separation here) acts as a flipper retractor and a flexor of the flipper blade at the elbow. a b


MUSCLE ANATOMY Axial Muscles. Most axial muscles are associated with the neck and tail of sea turtles. The majority of the neck muscles are illustrated with the neck circulation (Figs. 131, 141, 143-153). These include the transverse cervical muscles, and the biventer cervical muscle. Here, the superficial muscles of the throat and the jaw muscles are described. The tail musculature is not discussed because it has not been studied in any detail. The major deep muscles of the neck are the longus colli and retrahens colli The longus colli muscles are short, segmentally arranged, and travel obliquely between successive cervical vertebrae; they serve to extend the neck. The retrahens colli originate on the cervical vertebrae and extend posteriorly to insert on the dorsal vertebral elements of the carapace. They are neck flexors and retractors, to the extent that marine turtles extend and retract the neck. Head Muscles. Just beneath the skin of the throat is a thin layer of muscle, the intermandibularis which has fibers running between the two dentary bones. It inserts on a flat midline tendon (raphe) that runs the length of the throat (Fig. 121). The intermandibularis becomes the constrictor colli posterior to the jaw joint (Fig. 121), originating on a dorsolateral cervical tendon. Just deep to the intermandibularis are muscles running obliquely between the jaws and inserting on the hyoid, the geniohyoideus Posterior to the geniohyoideus is a pair of strap-like muscles, the coracohyoideus that extend to the hyoid apparatus from the coracoid (Figs. 122-123). These muscles assist in depressing the jaw, swallowing, and pumping the throat (gular flutter). They are innervated by the facial nerve. Muscles of the tongue, innervated by the hypoglossal nerve, and the glossopharyngeal nerve are not described here. The jaw muscles of turtles are mostly located inside the skull. Because of these deep positions, most are described but not illustrated. Unlike mammals, turtles lack a mandibularis muscle; instead they have an adductor mandibulae with several heads. The heads originate on the parietal, supraoccipital, quadrate, prootic, and opisthotic bones (Fig. 31) and converge on a tendon that inserts primarily on the lower jaw (dentary, with small insertions on the squamosal bone posterior to the jaw joint). Medial to the adductor mandibulae complex is a pair of connected muscles. The intermandibularismuscle runs from the lower jaw to the tendon of the pseudotemporalis muscle which itself continues to the parietal bone. These jaw closing muscles are all innervated by the trigeminal nerve The jaws Fig. 121. Ventral and superficial neck muscles. The constrictor colli muscle of the ventral neck is exposed lateral to and overlying the trachea. Connective tissue that loosely attached the muscle to the skin is still present on the turtle’s anterior neck. The midline raphe (tendon) is visible along the anterior half of the muscle. raphe intermandibularis muscle depressor mandibulae muscle constrictor colli muscle The Anatomy of Sea Turtles 68


The Anatomy of Sea Turtles 69 MUSCLE ANATOMY constrictor colli muscle trachea esophagus hyoid body process lateralis posterior branchiohyoideus muscle cut and reflected anteriorly carotid artery coracohyoideus muscle Figs. 122a and 122b. Dissection of the ventral neck muscles, showing the deep muscles (right in picture) and superficial muscles (left). The parallel fibers of the intermandibularis arise from the lower jaw, and terminate in the cut raphe (found overlying the hyoid body and anterior trachea). The branchiohyoideus is cut between the hyoid body and the hyoid process (process lateralis posterior) on the turtle’s left. The coracohyoideus travels along the trachea to the hyoid. The carotid artery lies deep to these muscles. a b are opened by the depressor mandibulae muscle, which has several parts. The depressor mandibulae arises from the quadrate, quadratojugal, and squamosal bones and inserts on the articular of the lower jaw; in Dermochelys a portion also inserts on the auditory tube. These parts are innervated by the facial nerve.


MUSCLE ANATOMY Figs. 123a and 123b. This oblique axial section through the neck of a hawksbill, is just posterior to the jaw joint ventrally and supraoccipital crest dorsally. The muscles, major blood vessels, trachea, and esophagus can be identified. Their relative positions and extent are seen in this dissection.supraficial adductor mandibulae hyoid element trachea carotid artery esophagus(collapsed)coracohyoideus muscle constrictor colli geniohyoideus muscle depressor mandibulae articular process transverse cervical muscle pterygoideus muscle(ventral part)adductor mandibulae spinal canal basiocciptal exoccipital otic cavity quadrate longus colli muscle splenius capitus muscleb a external jugular vein The Anatomy of Sea Turtles 70


The Anatomy of Sea Turtles 71 MUSCLE ANATOMY Posterior Muscles. The major posterior muscles can be identified after removing the rectus abdominus and the skin covering the hind legs and tail. Ventrally, these are the puboischiofemoralis externus and internus the pubotibialis ,the flexor tibialis complex and the ambiens (Figs. 125-126; see also Nervous System). These ventral hip muscles are innervated by the obturator and tibial nerves of the sacral (=lumbosacral) plexus. The puboischiofemoralis externus, a thigh adductor, covers much of the ventral pelvis, and arises from the ventral pubis, ischium, and membrane covering the thyroid fenestrae (Fig. 106); it inserts on the femur’s minor trochantor. Different parts of this muscle can either protract or retract the leg. The puboishiofemoralis internus is large in cheloniids and has both superficial and deep components. It may be absent in Dermochelys and replaced in function and position by the iliofemoralis When present, it originates on the dorsolateral pubis, ilium, and the sacral vertebrae. It inserts on the femur's major trochanter. The pubotibialis part of the flexor tibialis complex, is found in cheloniids but is absent in Dermochelys This muscle originates on the pubic symphysis and lateral pubis; it inserts on the tibia with the flexor tibialis internus The flexor tibialis internus, a Yshaped muscle, originates on the sacral and postsacral vertebrae dorsally, and ventrally on the pelvic symphysis and lateral pubis. It passes distally and wraps around the gastrocnemius muscle to insert on the tibia. The flexor tibialis externus has two heads (Figs. 125-126) and is somewhat medial to the internus. The dorsal head arises from the ilium and the ventral head from the posterior ischium. Both converge to insert, via a single tendon, on the tibia and the gastrocnemius muscle of the shank; some fibers insert on the skin and connective tissues of the shank. The adductor femoris (Fig. 126) originates on the lateral ischium and inserts on the posterior femoral shaft. The ischiotrochantericus (not shown), a leg retractor, originates on the anterior pubis and pubic symphysis. It inserts on the major trochanter of the femur. The dorsal hip and thigh muscles (illustrated in Circulatory Anatomy; Figs. 156-157 and Nervous System; Fig. 207), include the hip abductors: iliotibialis femorotibialis and ambiens The ventrally positioned ambiens (Fig. 125) originates on the pubioischiadic ligament, and inserts on the "patellar" tendon across the knee to the anterior tibia. The iliotibialis originates on the dorsal ilium and inserts with the ambiens on the patellar tendon. Deep to these two muscles, the femorotibialis (see Nervous System, Fig. 207), arises from the dorsal and anteroventral surfaces of the femur, and inserts with the iliotibialis and ambiens. The peroneal and femoral nerves of the sacral plexus innervate most of these dorsal hip muscles. The hind foot extensors (Fig. 124) are large sheet-like muscles originating on the dorsal and lateral femur and inserting on the dorsal and anterior fibula and digits. They flex the lower leg or extend the digits. Fig. 124. Anterior and dorsal foot extensors of a loggerhead right hind limb. The leg is abducted and flexed at the knee. The foot extensors flex the lower leg or extend and spread the digits.knee foot left thigh(medial)extensor digitorum


MUSCLE ANATOMY puboischiotibialis ambiens abdominal vein flexor tibialis tail puboischiofemoralis externus(cut) puboischiofemoralis internus Figs. 125a and 125b. The superficial ventral hip muscles. The puboischiofemoralis externus is an adductor of the leg. The puboishiofemoralis internus (the anterior ventral portion is seen here) is a protractor and abductor of the leg. The flexor tibialis complex, including the pubotibialis, flexes and retracts the leg and controls the shape of the trailing edge of the foot, perhaps during steering. More anteriorly, the ambiens is a weak adductor and protractor of the hind leg and can extend the shank. a b The Anatomy of Sea Turtles 72


The Anatomy of Sea Turtles 73 MUSCLE ANATOMY a pubotibialis(cut)adductor femoris ischial tuberosity sciatic nerve and peroneal nerves flexor tibialis(cut)flexor tibialis(cut)tail puboischiofemoralis internus Figs. 126a and 126b. The deeper ventral hip muscles are shown after removing the superficial limb retractors. The adductor femoris and puboishiofemoralis internus are antagonistic muscles, with the former adducting the thigh and the later abducting it. b


CIRCULATORY ANATOMY Circulatory AnatomyThe circulatory anatomy includes the heart, arteries, veins, and lymphatic vessels. The heart is multichambered and serves as the main pump. Arteries have thick walls of muscles and elastic fibers; they carry blood away from the heart.Veins carry blood to the heart; they have thinner layers of muscle and elastic tissues and tend to collapse in dead animals. Most veins contain valves. The lymphatic vessels transport tissue fluid from outside the circulatory system back to the blood. The lymphatic vessels are very thin walled and difficult to photograph. They surround the arteries and veins like sheaths. Heart. The heart is located within the pericardium and bordered ventrally by the acromion and coracoid processes (Figs. 127-129). Dorsally it is bordered by the lungs and laterally by the lobes of the liver. Within the pericardial sac, the heart is bathed with clear, colorless to slightly yellow pericardial fluid. All turtle hearts have four parts or chambers (Fig. 127): a sinus venosus two large atria and a ventricle The ventricle is thick-walled and internally subdivided into three compartments, the cavum venosum, cavum arteriosum and cavum pulmonae (not shown). These three ventricular compartments are separated only partially from one another. The posterior part of the pericardium and ventricle apex are attached to the peritoneum by the gubernaculum cordis (Fig. 129). This structure anchors the heart during ventricular contraction. brachiocephalic trunk pericardial fluid ventricle pulmonary artery left atrium left aorta right atrium pericardium right aorta abdominal veins Figs. 127a and 127b. Ventral heart.The heart is exposed after removing the pericardium. The more dorsal sinus venosus is not visible. Both aortas turn dorsally and are obscured partially by the brachiocephalic trunk. The pulmonary arteries arise from a common base, the pulmonary trunk. The abdominal veins from the posterior muscles are exposed posterior to the heart. a b The Anatomy of Sea Turtles 74


The Anatomy of Sea Turtles 75 CIRCULATORY ANATOMY vent pubis right aorta left aorta pulmonary artery left atrium ventricle right atrium acromion processes epipubic cartilage abdominal vein Figs. 128a, 128b, and 128c. Landmarks for location of the heart after removal of the plastron. The two acromion processes and acromialcoracoid ligaments frame the pericardium ventrally. When the plastron is removed carefully, the paired abdominal veins are preserved. They drain the ventral pelvic muscles; blood flows anteriorly returning toward the two lobes of the liver. View c shows a close-up of the heart after removal of the ventral pericardium. a b c


CIRCULATORY ANATOMY Arteries. Arising from the anterior and ventral part of the heart are the great vessels: two aortas and a pulmonary trunk (Fig. 129). The right aorta supplies blood to the head, limbs, and lower body, the left aorta to the viscera. The pulmonary trunk divides into the right and left pulmonary arteries taking the blood to the right and left lungs, respectively. The branches of the major vessels are good landmarks for locating organs and hence can serve like a map to locate specific structures. The right aorta gives off a branch right away called the brachiocephalic trunk and then continues posteriorly to the lower body where it joins the left aorta. The brachiocephalic trunk bifurcates; each branch produces a small thyroid artery to the thyroid gland anteromedially (Fig. 130). The branches of the brachiocephalic continue laterally as subclavian arteries (Figs. 129-130). The brachiocephalic trunk acts as a landmark for locating the thyroid and thymus glands (Glands; Figs. 159-160). pectoral muscle sinus venosus gubernaculum cordis pericardium ventricle pulmonary trunk brachiocephalic trunk carotid artery left atrium left systemic aorta right systemic aorta precaval veins esophagus trachea acromion process right atrium Figs. 129a and 129b. The four chambers of the heart can be identified in this ventral view. The ventral pericardium has been trimmed away to show both the heart and its great vessels. The apex of the ventricle is anchored to the pericardium and peritoneum posteriorly. The venous drainage from the anterior body to the precaval veins can just be seen lateral and anterior to the left atrium. a b The Anatomy of Sea Turtles 76


The Anatomy of Sea Turtles 77 CIRCULATORY ANATOMY thyroid gland esophageal arteries carotid artery ventral cervical artery thyroid artery thyroid artery pulmonary trunk left atrium ventricle right atrium brachiocephalic trunk right aorta subclavian artery Figs. 130a and 130b. Anterodorsal view of the heart and its major arteries. The great vessels emerge as three large vessels. The right aorta gives rise to the brachiocephalic trunk before it bends posteriorly. The thyroid arteries arise from the brachiocephalic trunk shortly after it bifurcates, (or, in this case, from the carotid arteries). It then gives rise to the left and right subclavian arteries. The right carotid is not dissected free of its connective tissue. The carotid arteries (Figs. 129-130), then the ventral cervical arteries arise from either the brachiocephalic trunk or the subclavian arteries lateral to the thyroid arteries (Fig. 130). The carotids (often termed common carotids) supply blood to the head. They bifurcate near the skull to form the external and internal carotid arteries. The ventral cervical arteries travel anteriorly then bifurcate to supply branches to the esophagus. The subclavian arteries continue laterally towards the flippers; near the junction of the scapula and coracoid they become the axillary arteries. There, branches to the scapular musculature arise ( anterior subscapular artery ). The axillary artery gives off both a branch to the carapace just prior to entering the forelimb, the marginocostal artery which travels posteriorly along the lateral aspect of the shell, and a branch to the ventral pectoral muscles, the pectoral artery (Fig. 131). As the axillary artery crosses the humerus, it becomes the brachial artery supplying radial, ulnar, then distally the digital arteries of the flipper. a b


CIRCULATORY ANATOMY internal carotid artery esophageal artery common carotid artery thyroid artery subclavian artery brachial artery left pulmonary artery radial artery ulnar artery digital arteries pulmonary trunk marginocostal left aorta gastric artery posterior gastric artery pancreaticoduodenal artery common iliac artery coeliac artery femoral artery sciatic artery vertebral artery epigastric artery gonadal artery adrenal artery dorsal aorta inferior mesenteric artery superior mesenteric artery right aorta brachiocephalic trunk costal artery external iliac artery internal iliac artery renal arteries external carotid artery } Fig. 131. Major arteries, ventral view. The major arteries are shown diagrammatically. Some subdivisions are not labeled for diagram clarity. These include the ventral cervical, axillary, anterior scapular, pectoral, anterior pancreaticoduodenal, and haemorrhoidal arteries. The major arterial and venous paths are summarized diagrammatically in Figs. 131-132. These diagrams show the most common routes taken by vessels. However, the circulatory system is among the most variable of all organ systems and hence, sometimes vessels branch in unique and unexpected manners. The Anatomy of Sea Turtles 78


The Anatomy of Sea Turtles 79 CIRCULATORY ANATOMY internal jugular vein external jugular vein axillary vein scapular vein subclavian vein dorsal brachial vein antebrachial vein internal brachial vein pulmonary vein left atrium transverse abdominal vein splenic vein intercostal veins marginocostal vein hepatic portal vein duodenal vein external iliac vein epigastric vein abdominal vein dorsal vertebral vein sinus venosus precava postcava thyroscapular vein efferent renal & gonadal veins ischiatic vein renal portal vein cloacal vein popliteal vein crural vein caudal vein femoral vein } } } } Fig. 132. Major veins, ventral view. Note that all branches are not shown or labeled to minimize diagram complexity. These include the azygos, transverse and central vertebral, eosophageal, hepatic, pectoral, pericardial, vesicular, pelvic, lipoidal, hypogastric, gastric, anterior and posterior pancreatic, mesenteric, common mesenteric, and inferior mesenteric.


CIRCULATORY ANATOMY Fig. 133. This lateral view of a green turtle has all superficial neck muscles cut and reflected dorsally. The arteries and veins were injected with latex to provide contrast. The carotid artery (at arrow) is deep and lies adjacent to the longus colli muscles of the cervical vertebrae. The left aorta, the middle of the three great vessels, turns dorsolaterally and passes the level of the stomach before producing three branches: the gastric artery the coeliac artery and the superior mesenteric artery The gastric artery bifurcates quickly and sends branches to the greater (lateral aspect) and lesser (medial aspect) curvatures of the stomach (Figs. 135-136). The coeliac artery branches shortly after leaving the left aorta and forms the anterior pancreaticoduodenal artery to the pancreas, duodenum and stomach and the posterior pancreaticoduodenal artery to the distal pancreas, duodenum, liver, and gallbladder (Fig. 136). The superior (or anterior) mesenteric artery gives off many branches that fan out through the intestinal mesenteries and supply the small intestines. After giving off the superior mesenteric artery, the left aorta continues posteriorly where it joins the right aorta (typically) to form a single dorsal aorta. The position where the two join is variable, but generally is within the middle third of the body. trachea dorsal aorta left aorta right aorta gastric artery coeliac artery superior mesentric artery Fig. 134. The ventral view of the left aorta and its major branches in a loggerhead after removal of the heart and viscera. Anterior is toward the top of the picture. The right aorta joins the left aorta very early in this loggerhead, just posterior to the origin of the superior mesenteric artery. The Anatomy of Sea Turtles 80


The Anatomy of Sea Turtles 81 CIRCULATORY ANATOMY liver right lobe liver left lobe stomach gastric artery acromio-coracoid ligament left coracoid process pyloric artery Figs. 135a and 135b. Circulation of the stomach. The ventral gastric artery drains to the lesser curvature of the stomach. It becomes the pyloric artery at the level of the pyloric sphincter. a b


CIRCULATORY ANATOMY deep pectoral muscle (right) duodenum reflected anteriorly & ventrally pancreas stomach spleen pyloric artery and coronary ventricular vein dorsal gastric artery posterior pancreaticoduodenal artery coeliac artery anterior pancreaticoduodenal artery Figs. 136a and 136b. Arteries and veins of the stomach, pancreas, and duodenum. The dorsal gastric artery drains to the greater curvature of the stomach. The coeliac artery, the second artery arising from the left aorta, supplies these branches to the duodenum, the stomach near the pyloris, and to the pancreas. a b The Anatomy of Sea Turtles 82


The Anatomy of Sea Turtles 83 CIRCULATORY ANATOMY The dorsal aorta (Figs. 134, 137-138) continues posteriorly and gives off paired branches, the costal arteries of the carapace, gonadal arteries to the ovaries or testes (there may be more than one per gonad), a pair of adrenal arteries and three or more renal arteries to each kidney (Figs. 137-138). A pair of epigastric arteries branches off the dorsal aorta at the level of the kidneys; they travel laterally to join the marginocostal artery of the carapace. Right external jugular vein with vertebral branches scapula esophagus caudal artery renal arteries right kidney left kidney adrenals dorsal aorta costal artery left lung right lung right aorta left aorta Figs. 137a and 137b. The carapace has been removed from this green turtle and the arteries injected with latex. The right and left aortas join along the middle third of the body. Costal (intercostal) branches extend anteriorly and across the body. Branches to the gonads, adrenals, kidneys, and hind limbs arise, then the caudal artery continues posteriorly along the midline to the tail and cloaca. This animal was missing its right hind limb. a b


CIRCULATORY ANATOMY vertebral arteries lung dorsal aorta adrenal glands adrenal artery gonadal artery right kidney left kidney renal arteries common iliac artery external iliac artery vertebral artery Figs. 138a and 138b. The carapace has been removed from this green turtle. The arteries are injected with latex to show the arterial branches to the gonads, adrenal glands, and kidneys. Variability is common in the circulatory system and is shown here. In this animal, the right gonadal artery is long and crosses dorsal and to the right adrenal gland, rather than extending lateral or anterior to it. There are 3 asymmetric (rather than symmetric) pairs of renal arteries supplying the kidneys. The epigastric arteries do not arise in the typical manner from the dorsal aorta, but instead from the left common iliac. The common iliacs continue as the external iliacs then divide to form the femoral and sciatic arteries. The internal iliacs arise directly from the dorsal aorta, in this case, turn ventrally, and supply blood to the bladder and large intestine. The caudal (vertebral) artery continues posteriorly along the midline. a b The Anatomy of Sea Turtles 84


The Anatomy of Sea Turtles 85 CIRCULATORY ANATOMY The arteries to the pelvic limbs, the external and internal iliac arteries may leave the dorsal aorta on each side via paired trunks (common iliacs), or they may branch off separately (Figs. 138-139). The external iliac supplies the femoral and sciatic arteries to the hind leg (Fig. 130). The internal iliac provides branches to the bladder and gonadal ducts, and the haemorrhoidal artery to the large intestine. The dorsal aorta then extends to the tail as the vertebral (caudal) artery (Figs. 131, 138-139). Pulmonary Trunk. The pulmonary trunk divides shortly after leaving the heart and supplies the right and left pulmonary arteries to the lungs (Figs. 129-130). The pulmonary arteries enter the lungs along the dorsal side of the bronchus, and travel posteriorly with the bronchi giving off multiple branches throughout the lung. The pulmonary artery walls are thickened as a muscular sphincter near the lungs. The lumen of each of the great vessels near the heart should be roughly uniform in thickness, except for the pulmonary arteries as they approach the lungs. Pulmonary Veins. Capillaries, venules (small veins), and veins within the lung coalesce into branches that drain into the pulmonary veins (not shown). The pulmonary veins travel along the ventral surface of each bronchus, then exit the lung anteriorly and arch medially. They enter the left atrium dorsolaterally. Systemic Veins. The venous circulation is described by tracing the veins away from the heart. However, it should be remembered that venous blood typically flows toward the heart. (It is noteworthy that flow direction can reverse in some veins.) Multiple terms are used to describe the major veins. The synonyms are given to clarify terminology. Venous blood from the body drains into the sinus venosus from 4 major veins: the left precava (= left common cardinal, = left superior vena cava), the right precava (= right common cardinal, = right superior vena cava), the left hepatic vein and the postcava (= posterior vena cava, = right hepatic vein; Fig. 132). The left and right precaval veins each drain the anterior body. Each precava receives branches from the subclavian and azygos veins and anteriorly from the internal and external jugular veins. The azygos vein is narrow and supplies the deep pectoral muscles (Fig. 140). The subclavian vein extends laterally. It receives the thyroscapular vein with thyroid branches from the thyroid gland and the scapular musculature, the scapular, transverse scapular and subscapular veins. The transverse scapular vein supplies drainage for the cephalic vein from the dorsal arm and the posterior and ventral flipper (Fig. 132). After receiving the thyroscapular branch, the subclavian vein extends laterally and forms the axillary vein in the axilla (armpit). Many branches arise in the axillary as the venous component of the rete system. The axillary components rejoin as the brachial vein in the upper arm, and then bifurcate as the internal brachial vein to the posterior flipper and the dorsal brachial vein to the anterodorsal flipper. As in the arterial system, a vascular circumflex forms near or just distal to the wrist, and receives drainage from the interdigital veins found medial to each digit. Because of the extensive connective tissue layers in the forearm and flipper blade, these vessels were traced by destructive dissection and so are illustrated diagrammatically (Fig. 132).


CIRCULATORY ANATOMY The external jugular vein is located relatively dorsal and superficial in the neck. The biventer cervical (=splenius capitus) and transverse cervical muscles are good dorsal landmarks for the external jugular. These muscles are obvious from the exterior and are to either side of the vessels; the external jugular is located deep and between them (Figs. 141-142), and medial to the transverse cervical muscle. Fig. 140. The azygos artery and veins and branches of the pectoral vein supply the deep pectoral musculature. Here the pectoralis major has been reflected anteriorly to expose the azygos vessels (at arrows) supplying the coracobrachialis-anterior and -posterior parts, as well as branches to the biceps profundus. Fig. 139. Dorsal arteries to the posterior musculature and kidneys of a loggerhead. kidney renal arteries dorsal aorta common iliac arteries caudal artery ilium left hind foot epigastric arteries The Anatomy of Sea Turtles 86


The Anatomy of Sea Turtles 87 CIRCULATORY ANATOMY dorsal shoulder muscles left forelimb biventer cervical muscle external jugular vein transverse cervical muscle head right forelimb Figs. 141a and 141b. Green turtle cervical circulation. The external jugular vein was dissected free on the turtle's right and injected to provide contrast. It shows the transverse cervical branch extending medially into the muscle. a b


The Anatomy of Sea Turtles 88 CIRCULATORY ANATOMY scapula cervical vertebra(cut)external jugular vein internal jugular vein precava head vertebral vein and branches transverse cervical vein Figs. 142a and 142b. Dorsal view of the neck of a green turtle with the carapace removed. The precava (superior vena cava) receives blood from the subclavian veins. The relatively small external jugular vein of green turtles receives relatively few branches when compared with the anatomy in other cheloniids. a b


CIRCULATORY ANATOMY vertebral branches of external jugular vein transverse cervical muscle retracted external jugular vein 1st left marginal 1st right marginal supraoccipital crest external jugular vein biventer cervical muscle nuchal scute Figs. 143a and 143b. Dorsal view of the external jugular veins and the vertebral vein. In this turtle the transverse veins are not obvious. There is an anterior bifurcation of the vertebral vein at the level of the neck rather than at the skull in this individual. The external jugular vein of this hawksbill receives dorsal and ventral vertebral branches from the cervical musculature proximally and distally. However, there are no branches along most of the intervening length. a b The Anatomy of Sea Turtles 89


The Anatomy of Sea Turtles 90 CIRCULATORY ANATOMY biventer cervical muscle external jugular vein transverse cervical muscle 1st left marginal scute nuchal scute Figs. 144a and 144b. The external jugular vein and its network of vertebral branches are obvious in this Kemp’s ridley. Multiple vertebral branches are common in this species between the prominent dorsal neck muscles. a b


CIRCULATORY ANATOMY biventer cervical muscle carapace transverse cervical muscle external jugular vein with vertebral branches skull Figs. 145a and 145b. Dorsal view close-up of a Kemp’s ridley external jugular vein, and its transverse branch arises medially (toward the left in this picture). a b The Anatomy of Sea Turtles 91

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CIRCULATORY ANATOMY biventer cervical muscle external jugular vein cervical branch of external jugular transverse cervical muscle 1st right marginal scute nuchal scute Figs. 146a and 146b. The external jugular vein is large and is associated with many anastomoses (networks of interconnected blood vessels) as well as cervical (vertebral) branches to the neck muscles of loggerheads. a b The Anatomy of Sea Turtles 92

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The Anatomy of Sea Turtles 93 CIRCULATORY ANATOMY transverse cervical biventer cervical external jugular vein Figs. 147a and 147b. Dorsal neck circulation in a leatherback.The external jugular vein is large and is associated with many smallcervical (vertebral) branches to the neck muscles The vessel is located deep between the transverse cervical and biventer cervical muscles. a b

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CIRCULATORY ANATOMY vertebral vein transverse cervical branches external jugular vein transverse cervical muscle esophagus(cut) Figs. 148a and 148b. Lateral view of the external jugular vein and both right and left transverse cervical branches in a green turtle. The vertebral vein is visible for part of its length, and is medial and deep to the cut skin of the dorsal neck. a b The external jugular vein (often termed the dorsal cervical sinus) is a commonly used venipuncture (blood collection) site in sea turtles. The external jugulars are large and extend from the base of the neck into the head where they drain the structures of the head. Each gives off at least one transverse branch that joins the other medially (Figs. 141147). Often a small central vertebral vein extends along the midline from the junction of the transverse cervical veins and provides drainage to the dorsal cervical muscles, cervical vertebrae, and the spinal meninges. In Chelonia mydas and Eretmochelys imbricata the external jugular is smaller in diameter and branches little (Figs. 141143, 148-149). This vessel branches frequently in the dorsal cervical region of Caretta caretta and Lepidochelys kempii (Figs. 144-146). In Dermochelys it branches near the head (Fig. 147). All species have vertebral branches from the external jugular draining the cervical structures. The Anatomy of Sea Turtles 94

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CIRCULATORY ANATOMY biventer cervical muscle cervical branch vein 1st left marginal scute 2nd left marginal scute hyoid process transverse cervical muscle lateral vertebral arteries external jugular vein nuchal scute Figs. 150a and 150b. The external jugular, injected with latex to provide contrast, is very large in this Kemp's ridley. After removing the connective tissue, the external jugular dropped to a more ventral position than would be found in life. Lateral vertebral arteries from the carotid are seen in this deep dissection. Fig. 149. Lateral view of hawksbill cervical circulation. The external jugular vein in hawksbills has few branches along most of its length. The vessel branches proximally to receive vertebral branches (near the nuchal scute) and ventrally, draining the ventrolateral neck muscles. Ventral cervical arteries are exposed adjacent to the trachea near the plastron. a b The Anatomy of Sea Turtles 95 biventer cervical muscle transverse cervical branches trachea external jugular vein

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CIRCULATORY ANATOMY vertebral branches trachea left flipper right flipper cut muscles head external jugular vein Figs. 151a and 151b. This lateral view of a Kemp’s ridley shows the many vertebral branches off the external jugular going to the deep cervical musculature. a b The Anatomy of Sea Turtles 96

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CIRCULATORY ANATOMY biventer cervical muscle transverse cervical muscle external jugular vein 1st left marginal scute nuchal scute Figs. 152a and 152b. This lateral dissection of a loggerhead's external jugular shows the extensive branching that is typical of this species. The transverse cervical muscle has been split along its length to expose the vein. Both the muscles and veins are displaced ventrally because their supporting connective tissues have been removed. a b The Anatomy of Sea Turtles 97

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CIRCULATORY ANATOMY The internal jugular vein is smaller in diameter than the external jugular and is found more deeply adjacent to the longus colli muscles. It receives multiple branches from the esophagus ( esophageal veins ) before it drains into the precava (Fig. 153). Fig. 153. The internal and external jugular veins from the precava are exposed in this dissection of a green turtle. The external jugular vein (downward pointing arrow) is mostly covered by the cut neck musculature which has been reflected dorsally. The internal jugular (upward pointing arrow) is partially injected with latex. The internal jugular vein is usually accompanied by the vagus nerve, however it is not distinct in this photo. The Anatomy of Sea Turtles 98

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CIRCULATORY ANATOMY left flipper cephalic vein scapula thoracodorsal artery precava transverse scapular vein subscapular vein and artery scapular vein Figs. 154a and 154b. Venous and arterial branches of the posterior aspect of the flipper. The cephalic vein from the flipper drains into the transverse scapular vein along the scapular musculature, then to the scapular vein, which then joins the precava. The thoracodorsal artery is a branch from the subclavian or the brachial in most turtles. a b The Anatomy of Sea Turtles 99

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The Anatomy of Sea Turtles 100 Venous return from the posterior body is by both direct routes (to the postcava and the left hepatic vein) and indirect routes (via the renal portal and hepatic portal systems). Portal systems are those that start and end in capillaries. The renal portal system consists of veins draining into the postcava, abdominal, renal portal, and external iliac veins. The hepatic portal system includes the veins draining into the hepatic portal, common mesenteric, mesenteric, and duodenal veins. These will be discussed separately. The postcava runs anteriorly from the capillaries of kidneys through the right lobe of the liver (Fig. 132). It emerges from the right lobe of the liver and enters the right side of the sinus venosus. Posteriorly, the postcava receives multiple pairs of renal veins from the ventral surface of the kidneys. Gonadal veins also pass from gonads, through the kidneys, and to the postcava. Branches from the iliac veins drain the pelvic musculature, and the costal veins from the carapace occasionally drain into the postcava. Anteriorly it receives multiple hepatic veins from throughout the liver. The postcava is part of the renal portal system. The left hepatic vein drains blood through the liver and from the paired abdominal veins (Fig. 132) which are located just anterior to the pelvis and in the peritoneum. There is usually a transverse abdominal vein connecting the abdominal veins. Blood can flow in either direction through this vein. The abdominal veins receive pectoral veins (Fig. 127) descending from the pectoral muscles. Pericardial veins usually enter the abdominals near the pectoral veins and posterior to these, a pair of vesicular veins enters from the bladder. The abdominals extend along the dorsal pelvic musculature and receive pelvic veins from the left and right sides. In the hind limb, crural veins extend from the medial to the posterior thigh and shank. Crural branches from the shank, the tibial and popletial veins plus the femoral veins (from the dorsolateral thigh and shank; Figs. 132 and 156) drain to enter the abdominals, usually just posterior to the pelvic veins. Paired lipoidal veins from the left and right inguinal fat pads, enter the abdominal veins from near the crural veins. External iliac veins drain into the abdominals at or near the junction of the femoral and crural veins with the abdominal veins. The epigastric vein (Fig. 157) extends from the marginocostal vein on each side and travels with the epigastric artery along the posterolateral margin of the carapace. It runs along the upper thigh, and drains into the external iliac vein. CIRCULATORY ANATOMY coracoid liver testis post cava coracoid kidney Fig. 155. Ventral view of the postcava. The postcava emerges from the liver and passes to the kidneys. Blood is drained from the kidneys and posterior body to the liver.

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CIRCULATORY ANATOMY flexor tibialis externus pubotibialis crural vein femoral artery popletial vein gastronemius muscle ventral flexor tendon foot pelvis Figs. 156a and 156b. The right hind limb of this loggerhead shows the positions of the femoral artery, crural, and popletial veins. These arteries and veins travel with the sciatic nerve. a b The Anatomy of Sea Turtles 101

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The Anatomy of Sea Turtles 102 CIRCULATORY ANATOMY peritonium with fat rectus abdominus epigastric vein iliotibialis flexor tibialis caudal vein tail left hind limb Fig. 157. Lateral and posterior view.The epigastric vein travels dorsally to the dorsal hind leg extensors (iliotibialis) and flexors (flexor tibialis). This vein is medial to the marginal scutes and just ventral to the dorsal fat layer. It receives drainage from into the caudal veins just dorsal to the tail. The paired renal portal veins receive the ischiadic veins from the posterior hip muscles. The caudal veins (Fig. 157) extend along the lateral tail and receive the cloacal veins medially from the cloaca and rectum. The caudal veins drain into the ischiadic veins, as well as the epigastric vein in sea turtles. The renal portal vein also receives drainage from the narrow vertebral veins which are found lateral to the vertebral column and enter the kidneys anteriorly and dorsally. The vertebrals receive costal veins from the shell, which are connected laterally with the marginocostal vein (Fig. 132). From the cloaca, bladder, rectum, and in males, the penis, blood drains to the hypogastric vein which enters the kidneys posteriorly and ventrally. The renal portal veins drain from the dorsal kidney capillaries into the external iliacs at the level of the epigastric veins, or into the posterior extent of the abdominal veins. The hepatic portal vein receives drainage from the abdominal veins. It passes dorsally between the right and left lobes of the liver. Anteriorly, it receives several branches from the stomach, the gastric veins with several branches forming the anterior a b

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pancreatic veins (along the left half of the pancreas), the posterior pancreatic veins (from the right half of the pancreas), and the long duodenal vein (Figs. 134 and 136). The spleen, found near the posterior end of the pancreas, is highly vascular and is drained by several splenic veins to the hepatic portal vein (Fig. 158). More posteriorly, multiple mesenteric veins travel with the mesenteric arteries radiating from the small intestines and through the fan-shaped mesentery (Fig. 158). The mesenteric veins converge on the common mesenteric vein which drains into the hepatic portal vein. The inferior mesenteric vein drains branches from the large intestine up to the iliocaecal junction (where the large intestine meets the ileum), then itself enters the common mesenteric vein leading to the hepatic portal vein. CIRCULATORY ANATOMY ventricle stomach spleen large intestine mesentery} } mesenteric veins Figs. 158a and 158b. The spleen is exposed to the left of the stomach and distal to the pancreas (covered by mesentery). Several splenic veins cover the spleen's surface. Mesenteric veins, in the fat-rich mesentery, drain blood returning from the small intestines. a b The Anatomy of Sea Turtles 103

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NOTE: Cavum arteriosum doesn’t lead to arterial arches.Circulation through a turtle heart during ventilation. Circulation through a turtle heart during apnea(inferred from Shelton and Burggren, 1976) CIRCULATORY ANATOMY Circulation Through the Heart. The route blood takes though the heart differs depending upon whetherblood is shunted toward the lungs and the body, or primarily toward the body. Unlike mammalian cardiopulmonary systems, the pulmonary and systemic blood flows are not always separate. The extent of separation between the pulmonary and systemic circuits of flow differs somewhat between Dermochelys and the cheloniids. There is a nearly complete separation of systemic (body) and pulmonary (lung) circulation in the leatherback heart, but the intracardiac flow is less well separated into pulmonary and systemic outflows in the cheloniid species. Studies of turtles generally show that whether blood is shunted to or away from the lungs is a function of arterial blood gas levels. Venous blood returning from the head, limbs, and body enters the sinus venosus, then flows to the right atrium. From the right atrium, blood enters the ventricle where it flows along at least two possible routes. The diagram below (Fig. 159) summarizes the route blood takes through the heart. Blood from the kidneys returns to the left atrium via the pulmonary veins. It then flows from the left atrium to the ventricle and usually out through the aortas to the body. Fig. 159. Circulation through a turtle heart during breathing and during breath-holding (apnea). The Anatomy of Sea Turtles 104

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LUNG and AIRWAY ANATOMY The Anatomy of Sea Turtles 105 Lungs and AirwaysThe pulmonary system is composed of the glottis trachea a bronchus to each lung, and the left and right lungs The airways begin at the glottis, which is located in the middle to posterior portion of the tongue (Fig 160). The glottis and its muscles are supported ventrally by the hyoid apparatus. The glottis opens during air passage and is closed during breath-holding. The glottis leads directly into the trachea, which is supported by complete cartilaginous rings that are usually white, except in decomposing animals or some turtles with pulmonary disease. The trachea is long and bifurcates into two bronchi dorsal and anterior to the heart. These then enter the anterior part of the lungs next to the pulmonary arteries. The bifurcation begins internally, anterior to the external division to form the bronchi. The bronchi extend for virtually the length of the lungs and have many openings into the complex internal lobes of the lungs (Fig. 161). Unlike the bronchi of mammalian lungs, these openings lead to chambers that are not supported by cartilage. There are no secondary bronchi in sea turtles. Fig. 160. Parasagittal section of a hawksbill showing the airway. The hyoid apparatus, including both bony and cartilaginous portions, supports the glottis ventrally. The glottis, located between the hyoid and the surface of the tongue, is closed in this dissection.The large tracheal diameter is maintained by cartilaginous rings. The trachea is lined by smooth epithelium.brain olfactory sac mouth tongue hyoid glottis trachea {

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The Anatomy of Sea Turtles 106 LUNG and AIRWAY ANATOMY The lungs are located dorsally and are attached dorsally to the carapace and vertebral column. In some species, (e.g., L. kempii and C. caretta ) the lungs are more closely attached to the vertebral column than in other species. Ventrally, the left lung is attached to the stomach via the gastropulmonary ligament The right lung is attached to the right lobe of the liver by the hepatopulmonary ligament Posteriorly, the lungs attach to the peritoneum that overlies the kidneys and adrenal glands and are adjacent to the gonads. The medial border of each lung is firmly attached (Fig. 162) via fibrous connections to dorsolateral surfaces of the vertebral column. Fig. 161. Longitudinal section through a loggerhead bronchus. The lungs of cheloniids are spongy in construction and red in color. They also have a large surface area but are not as densely constructed as the lungs of leatherbacks. The large-bore trachea has many openings to the chambers of the lung along its length. These openings are not supported by cartilage once they leave the bronchus. The unsupported airways extend to the air exchange surfaces called faveoli and ascini. The trachea and bronchus are supported by cartilage, which resists collapse during ventilation and diving.

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All sea turtles have multichambered lungs (there are multiple lobes contained within the body of the lung). The lobes are not obvious externally. The lung tissue is spongy and highly elastic (Figs. 161 and 163) in sea turtles. Ventilation of the lungs occurs without the assistance of a diaphragm. Marine turtles ventilate by movements of ventral muscles of the pelvic and pectoral girdles that attach to the plastron, compression of the inguinal region, and rocking of the shoulder muscle masses to change the pressure within the pleuroperitoneal cavity. Sea turtles have a large tidal volume. Under normal circumstances, they breath-hold until blood oxygen levels drop to low levels. LUNG and AIRWAY ANATOMY Fig. 162. CT scan showing the lungs in a Kemp's ridley. This CT shows the position, form, and the extent of the lungs and airways in a living Kemp's ridley turtle. The medial surfaces of the lungs are attached tightly to the vertebral column. Fig. 163. Longitudinal section through a leatherback lung. The lungs of leatherbacks are characterized by more dense construction. The high surface area, dense parenchyma, high levels of connective tissue, and extensive blood supply make leatherback lungs particularly spongy and deep red in color. The Anatomy of Sea Turtles 107

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The Anatomy of Sea Turtles 108 GASTROINTESTINAL ANATOMY Figs. 164a and 164b. The gastrointestinal tract with digestive glands and the spleen. The GI tract from the esophagus to the rectum from a Kemp’s ridley turtle shows the different regions as well as the associated digestive glands, the liver and pancreas. The gall bladder stores bile, produced by the liver, and releases it through the common bile duct when food enters the duodenum. The spleen, located at the distal end of the pancreas, is not a digestive gland; rather it is a lymphoid organ in turtles involved in immunological activity. Gastrointestinal TractThe gastrointestinal tract (GI tract or gut) extends from the mouth to the cloaca (Fig. 164). It is demarked by structural and functional divisions. The mouth captures and processes food. The esophagus conveys food to the stomach and expels excess water. It also works with the tongue in swallowing. The stomach starts the chemical and physical process of digestion. In the small intestines digestive enzymes are added to food to break down proteins and complex carbohydrates. The small intestines are regionally specialized to absorb amino acids, carbohydrates, sugars, water, fatty acids, and minerals (particularly calcium and phosphorus). The large intestine (colon) typically reclaims water. The length of the gut is somewhat related to diet. It is proportionally longer in green and leatherback turtles than in loggerheads, ridleys, and hawksbills. ileum colon jejunum pancreas duodenum liver right lobe liver left lobe stomach pylorus spleen gall bladder esophagus a b

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GASTROINTESTINAL ANATOMY The mouth includes several GI, respiratory, and ear structures: the mandibles and the pharynx includes the palate, esophagus, glottis, Eustachian tubes, and internal choanae (Fig. 165). For convenience, these structures will be described together here. The glottis and internal choanae are part of the respiratory system and the Eustation tube connects the pharynx with the middle ear cavity. The tongue is fixed to the floor of the mouth and is not protrusible. The glottis is located on the middle part of the tongue (see Sense Organs, Fig. 209), just posterior and ventral to the internal choanae (internal nares); it acts as a valve to open and close the airway. The esophagus starts at the back of the tongue; it is a muscular tube that leads to the stomach. It passes slightly dorsal and to the right of the trachea. The Eustachian tubes (one on each side), are found in the posterolateral aspects of the mouth, medial to the jaw joint; they function in maintaining normal pressure in the middle ear (Fig. 165). internal choanae palate Eustachian tubes esophagus(cut) Figs. 165a and 165b. Ventral view of the palate with the tongue and hyoid apparatus cut away. The roof of the mouth has internal choanae (internal nares) that open above the glottis (removed in this picture). In the posterior lateral parts of the palate, near the jaw joint, are the openings to the Eustachian tubes, which lead to the middle ear cavity. a b The Anatomy of Sea Turtles 109

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The Anatomy of Sea Turtles 110 GASTROINTESTINAL ANATOMY The esophagus (Fig. 166) is lined with papillae that are sharp and keratinized; they point inward towards the stomach. The papillae end where the esophagus joins the stomach (Fig. 166). The papillae are presumed to trap food while excess water is expelled prior to swallowing. In Atlantic green turtles, the esophagus enters the stomach in a smooth transition. However, in Pacific green turtles, there is a muscular specialization at the base of the esophagus called a crop Its function is unclear. In cheloniids, the esophagus descends to a position just inside the plastron and bends to the left in an S-shaped curve to join the stomach. In Dermochelys the esophagus is exceptionally long and extends almost half the length of the body before looping to the left, and returning anteriorly almost to the level of the axilla. There, the esophagus bends left again and joins the stomach (Fig. 167). esophagus transitional papillae gastroesophageal sphincter stomach rugae} Figs. 166a and 166b. The esophagus and anterior stomach lining. The papillae that line the esophagus are keratinized for most of the length of the esophagus. They end abruptly; several flat, transitional papillae, lacking keratin line the esophageal wall at the level of the gastroesophageal sphincter. Posterior to this sphincter, the stomach lining is very smooth and has no papillae. a b

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GASTROINTESTINAL ANATOMY Figs. 167a and 167b. Ventral view of a leatherback hatchling's viscera and heart. This dissection of a leatherback posthatchling shows the extremely long esophagus, large stomach, and small intestines. On the animal's right is the remaining yolk sac. The yolk sac can persist well after the time that the animal has begun feeding. In this animal, the coracoid processes were cut away and the acromion processes reflected anteriorly to provide a clear view of the heart and liver. The ventricle is pushed anteriorly exposing the sinus venosus, which was injected with latex to provide contrast. right acromion process gall bladder cut pectoral muscle liver right lobe right atrium pubis small intestine yolk sac colon trachea liver left lobe left atrium sinus venosus ventricle reflected anteriorly esophagus stomach duodenum esophagus pubic cartilage a b The stomach is on the animals left side and curves around the more medially located liver and pericardium. It is attached to the liver's left lobe by a gastrohepatic ligament and the left lung by a gastropulmonary ligament The stomach is smooth-walled along its length. It ends in a short muscular region, the pylorus (= pyloric sphincter or valve ). The pylorus is usually constricted and the intestinal lining on the duodenal side of the sphincter differs from that of the stomach (Fig. 169). The pancreas runs distally along the duodenum from the pylorus to just past the common bile duct (Fig. 170). Both the pancreas and the common bile duct (from the gall bladder) deliver digestive enzymes to the duodenum. The common bile duct enters the duodenum via a small papilla, the ampulla of Vater on the duodenum’s internal surface. Its location can be identified from the green bile stain (Figs. 170-171). The pancreatic duct (not shown) is difficult to locate in all but the largest turtles; it enters the duodenum near or in The Anatomy of Sea Turtles 111

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common with the common bile duct. The duodenum's lining is textured and, in some species, it is "honey-combed" in appearance (Fig. 171). This textured lining is associated with increased surface area and is well-developed in green turtles and leatherbacks. It is not as pronounced in the carnivorous/omnivorous species (e.g., loggerheads, ridleys, and hawksbills). The transitions from one type of small intestine to the next ( duodenum to jejunum to ileum ) are often difficult to identify. Gross differences are often not obvious and are best confirmed by histological examination for the functional characteristics of the tissues. The transition from ileum to colon is clear. The ileum ends in a muscular sphincter, the iliocaecal valve The proximal end of the colon is a caecum (pouch) that bulges somewhat more than the remaining large intestine (Fig. 77). It is more prominent in green turtles than other species.The colon narrows somewhat past the caecum; it is constricted weakly by segmentally arranged bands of muscle. Distally, the colon tapers to form a muscular rectum, which is often pigmented; its muscular walls are thickened and folded (Fig. 172). GASTROINTESTINAL ANATOMY stomach pyloric sphincter duodenum Figs. 169a and 169b. Linings of the stomach and duodenum. The stomach and duodenum are separated by a short muscular sphincter, the pylorus. While stomach lining is generally smooth, that of the duodenum is often textured. In the leatherback and green turtle, there are the overlapping crypts containing mucus found along the length of the duodenum and into the jejunum. a b The Anatomy of Sea Turtles 112

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GASTROINTESTINAL ANATOMY Fig. 171. Longitudinal section through the liver and gallbladder. The walls of the gallbladder are removed dorsally to expose the common bile duct to the duodenum. Fig. 170. Longitudinal section of the duodenum. The common bile duct opens into the duodenum at a papilla (termed the Ampulla of Vater). The common bile duct extends from the gallbladder to the duodenum.liver liver gallbladder gallbladder bile duct ampulla of Vater(bile duct papilla)duodenum pylorus duodenum The Anatomy of Sea Turtles 113

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The Anatomy of Sea Turtles 114 GASTROINTESTINAL ANATOMY Figs. 172a and 172b. Ventral view of the posterior viscera. The rectum (collapsed here) narrows as it joins the cloaca. The urinary bladder, seen just above the r ectum, enters the cloaca ventrally. The dorsally-located kidneys produce urine that travels though the ureters to enter the dorsal cloaca. Several renal veins are exposed medial to the kidney. The testis of this immature male is still attached to the peritoneum (and is located anatomically ventral to the kidneys). urinary bladder rectum kidney renal veins cloaca ureter colon kidney testis dorsal pelvic girdle reflected posteriorly right coracoid cartilage and deep pectoral muscle left coracoid cartilage liver left lobe a b The rectum empties into the cloaca (Fig. 171), a chamber that also receives the urine from the kidneys, eggs or sperm, and connects ventrally into the urinary bladder. The cloaca empties to the outside via the cloacal opening or vent. Each function of the cloaca is associated with a region into which the products empty. The coprodeum received feces from the rectum. The urodeum is associated with the urinary papillae and the opening of the urinary bladder. The proctodeum is the most distal region and is associated functionally with copulation and structurally with proximity to the genital ducts.

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GLANDS GlandsGlands are often lobular and may have ducts or are ductless. They are involved the in production of peptides and steroids, which can form skin coatings (waxes), enzymes, or hormones. Glands are either formed in the skin and its related structures (ectodermal in origin) or from deeper within the body (mesodermal in origin). Glands are discussed below by region and function, when known. The salt (lacrimal) gland (Figs. 81 and 172) is the largest gland in the head and is found dorsal and medial to the eye. These glands are large in all sea turtles, but are especially hypertrophied in Dermochelys (Fig. 172). The salt gland is responsible for removal of excess salt from the body. Anterior to the eye, there is a small Harderian gland associated with lubricating the eye. Sea turtles, like most aquatic lower vertebrates, appear to lack oral glands. dorsal nares cartilaginous septum salt gland sella tursica neurocranium salt gland Figs. 172a and 172b. Dorsal view of the salt gland and braincase of a leatherback. The extremely large salt glands dominate the skull space lateral to the braincase and dorsal, medial, and posterior to the eye. The brain has been removed leaving the braincase with the sella tursica retaining the pituitary gland. a b The Anatomy of Sea Turtles 115

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The Anatomy of Sea Turtles 116 GLANDS The ductless pineal gland (epiphysis) is a dorsal extension of the brain; it connects indirectly to the dorsal surface of the braincase, it is located deep to the frontoparietal scale in cheloniids and the "pink spot" in Dermochelys (illustrated in the Nervous System, Figs. 193-194, 196, 198-201). It is responsible for modulating biological rhythms. The pituitary gland (hypophysis) is found in a cavity, the sella tursica in the floor of the braincase (Nervous System, Fig. 190). The pituitary is composed of two parts, the neurohypophysis (infundibulum) and the adenohypophysis The neurohypophysis produces releasing hormones (e.g. oxytocin) and release-inhibiting hormones (e.g. antidiuretic hormone), while the adenohypophysis produces growth hormone, prolactin, thyroid-stimulating hormone, gonadotropins, adrenocortacoids, and melanophore-stimulating hormone. More posteriorly are several glands derived from pharyngeal pouches of the embryo. These ductless glands are the thyroid, thymus, parathyroid and ultimobranchial bodies All are located in the ventral neck and upper body. The thyroid gland can be located medially to the the acromion processes (Figs. 75 and 173) by tracing along the brachiocephalic trunk where it gives rise to thyroid arteries (soon after its bifurcation to form the subclavian arteries). The thyroid arteries “frame” the single thyroid gland that is encased in connective tissue (Fig. 173). The thyroid is round and is often coated with a thin layer of fat. In fresh specimens, it is bright red. However, in turtles that have been frozen, then thawed, or that have started decomposing, it may become brown. It is gelatinous in texture in fresh and fresh-frozen animals. In decomposing carcasses, it liquifies. The thyroid is involved with increasing oxygen consumption when reptiles exceed their preferred body temperatures, and it functions in gonadal maturation. The thymus glands can be located by tracing along the subclavian arteries and palpating for a dense, laterally elongated structure (Figs. 174-175). There is a gray to pink thymus gland on each side of the body that is composed of small lobes. It is usually associated with fat. The thymus glands are more dense and compact than the fat. They are often easiest to find by palpating. The thymus glands play a role in immune responses. In chronically ill animals this gland is frequently thin and diffuse. Fig. 173. Thyroid gland in ventral view, medial to the acromion processes. The thyroid is the dark, round structure at the tip of the pointer. The heart has not been exposed yet. Anterior is toward the top of the figure. The two acromio-coracoid ligaments extend posteriorly from the acromion process.

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GLANDS The parathyroid and ultimobranchial bodies are difficult to identify and can only be distinguished from one another histologically (Fig. 176). They are very small and located along the carotid and ventral cervical arteries. Generally, the parathyroid glands are the more anterior glands and the ultimobranchial bodies are more posterior. They are brown or dark pink in color. They are best located by feeling for the round, dense glands, then using careful dissection. The two kinds of glands have antagonistic functions. The parathyroid gland releases parathormone, which stimulates the mobilization of calcium and phosphorus from storage (usually bones).The ultimobranchial body releases calcitonin, which lowers blood levels of calcium and phosphorus. Fig. 175. Ventral view of the two thymus glands, just below the fingertips, are located adjacent to the subclavian arteries. They are anterior to the heart and lateral to the thyroid gland (seen as the smooth oval tissue anterior to the great vessels). Fig. 174. Ventrolateral view of the neck structures. Positions of the trachea (with cartilaginous rings) and esophagus to the animal's right provide landmarks. The head is removed; anterior is toward the top of the picture. The lobular right thymus gland is at the bottom of the picture. The Anatomy of Sea Turtles 117 esophagus trachea thymus thyroid heart subclavian arteries thymus

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The Anatomy of Sea Turtles 118 GLANDS subscapular artery subclavian artery carotid artery internal jugular vein thymus gland right aorta left aorta pulmonary artery ultimobranchial body right atrium(reflected medially) left atrium(distended) ventricle Figs. 176a and 176b. Ventral view of an ultimobranchial body (or parathyroid) and thymus gland. The carotid and ventral cervical arteries are the best landmarks for locating the parathyroid and ultimobranchial glands. The glands tend to be associated with the connective tissue on the dorsal surfaces of the arteries. Typically, 2-4 glands are present on each side. The large thymus gland, deep to the subclavian artery, is seen near the top of the picture. a b

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GLANDS The liver is the largest visceral organ and is located ventrally, but deep to the pectoral skeleton and peritoneum (Fig. 177). It is dark brown to reddish brown and composed of two lobes joined by one or more connecting strips of hepatic tissues. The right lobe houses the gallbladder on its ventral surface and is typically larger than the left lobe (Fig. 177). The liver is highly vascular; it receives blood from the hepatic portal vein and the hepatic artery. Blood from the body drains from the liver via the hepatic veins to the sinus venosus. The liver contains many bile ductules and hepatocyte cords. The hepatocytes manufacture bile which drains via bile ductules into the gallbladder. The gallbladder stores bile which is then transported via the common bile duct to the duodenum in response to the presence of fats. Bile contains the enzymes involved with fatty acid breakdown. The liver plays a major role in carbohydrate and protein metabolism as well as in removal of toxins from the blood. Blood from the stomach and intestines percolates through hepatic tissues where carbohydrates, amino acids, and peptides are broken down. Other liver cells make serum albumin and a number of clotting factors. Fig. 177. The liver is exposed in a green turtle. The left and right lobes are located lateral and slightly dorsal to the heart. Both lobes receive blood from the hepatic portal system. Fig. 178. Dorsal view of the duodenum (at top) with the pancreas, spleen (at arrow), and a portion of the liver's right lobe. liver left lobe liver right lobe The Anatomy of Sea Turtles 119

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The Anatomy of Sea Turtles 120 GLANDS Pancreas. The pancreas is located along the duodenum just past the stomach (Fig. 178-179). It is a smooth and thick tissue that extends as an irregular strip past the common bile duct and often ends at or just past the spleen. It is pink to yellow orange in color. The pancreas is a digestive gland as well as an endocrine gland and produces pancreatic polypeptides which stimulate flow of gastric juices in the stomach. Other pancreatic cells produce insulin which assists in the metabolism of glucose. Some pancreatic cells produce glucagon which stimulates the breakdown of glycogen to increase blood glucose levels. Rathke's glands are located deep to the inframarginal scutes in Lepidochelys (Figs. 180181) and in the posterior axilla and anterior-most inguinal regions in Eretmochelys and Chelonia (Figs. 182-183). Rathke’s glands have not been identified in Caretta and Dermochelys While prominent, they show no change with reproductive condition or season. Their function is unknown. The secretions of the glands have been hypothesized to play various roles including intraspecific communication, anti-fouling, and/or anti-microbial function. Fig. 177. The long narrow pancreas is seen just below the duodenum (at arrow) in this loggerhead dissection. It is encased in the mesentery. A large artery in the mesentery is seen supplying branches to the proximal and distal pancreas. The dark, oval spleen is seen below the pancreas, above the loops of small intestines.

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GLANDS inframarginal scutes inframarginal pores Figs. 180a and 180b. Inframarginal Pores. Ridley turtles have pronounced inframarginal or Rathke's pores associated with each inframarginal scute. The pores lead to the Rathke's gland. In mature turtles, with fully developed plastron bones, the ducts from these pores are surrounded by bone. They leave foramina (holes) in the hyoplastron and hypoplastron bones. Figs. 181a and 181b. When the plastron is removed, the gray-green Rathke's gland and its ducts are exposed. Each duct leads to an inframarginal (Rathke's) pore. The gland is typically embedded in fat. It extends the length of the inframarginal scutes from the axilla to the anterior extent of the inguinal region. ducts from inframarginal pores to Rathke’s gland Rathke’s gland marginal scute fat a b a b The Anatomy of Sea Turtles 121

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The Anatomy of Sea Turtles 122 GLANDS Figs. 182a and 182b. Rathke's pores in a hawksbill. The posterior Rathke's pore in this hawksbill is found in the anterior-most inguinal scale. Figs. 183a and 183b. Anterior Rathke's pore in a green turtle. The anterior Rathke's pore in this green turtle is found in the most posterior and lateral axillary scale. Rathke's pores and Rathke's glands are also found in Chelonia mydas and Eretmochelys imbricata They are restricted to the posterior axilla and the anterior-most inguinal scales. The pores typically do not extend to the inframarginal scutes (Figs. 182-185). Rathke’s pore Rathke’s porea b a b

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Figs. 184a and 184b. Rathke's gland and pore in a green turtle. As the plastron is removed, the gray Rathke's gland can be found embedded in fat just deep to the Rathke's pore. Figs. 185a and 185b. Posterior Rathke's pore in a green turtle. The posterior Rathke's pore in this green turtle is found in the most anterior and lateral inguinal scale. GLANDS Rathke’s pit Rathke’s gland Rathke’s porea b a b The Anatomy of Sea Turtles 123

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The Anatomy of Sea Turtles 124 GLANDS dorsal aorta adrenals kidneys Figs. 186a and 186b. Adrenal glands. This dorsal view of the adrenal glands shows their elongate shape and their position just anterior and medial to the kidneys. The adrenal arteries are not clear in this dissection. The left adrenal is crossed by a costal artery. a b The adrenal glands (Fig. 186) are paired, tan to pink in color and are located lateral to the dorsal aorta, usually anterior to the renal arteries. They are usually medial to, and just anterior to, the kidneys. The adrenal glands develop from the anterior (cranial) poles of the embryonic kidneys. The paired adrenals are elongated along the anteriorposterior axis and oval in cross section. They are composed of two intermingling tissue types: interrenal bodies, that produce steroids (corticosterone) and chromaffin bodies that produce catecholamines such as adrenaline (epinephrine and norepinepherine). Unlike mammals, these tissues are not organized into a distinct cortex and medulla.

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NERVOUS SYSTEM Nervous SystemThe brain or central nervous system ( CNS ) of sea turtles is longitudinally arranged along the midline of the skull (Fig. 187). The brain is housed in a tubular braincase, composed anteriorly of the following bones: ethmoid, epiotic, prootic, opisthotic, basisphenoid, laterosphenoid, and otic (Figs. 26 and 30). Posteriorly it is completed by the basioccipital, exoccipital, and supraoccipital. It is roofed by the parietal and frontal bones (Fig. 25). Two tissue layers, the meninges cover the brain. The outer menix (singular) is the tough dura mater A more delicate leptomenix (sometimes termed the pia mater) lies directly on the brain's surface (Fig. 187). There are both subdural (beneath the dura mater) and epidural (above the dura mater) spaces within the brain case. Epimeningeal veins occupy some of the epidural space. The brain is bathed in clear cerebral spinal fluid produced by the tela choroidea a vascular region of the brain (Fig. 187). Figs. 187a and 187b. Exposed brain and cut meninges. The anterior and posterior extent of the dura mater and a vascular portion of the leptomenix (= pia mater) are seen in this exposed loggerhead brain. In life, both meninges would envelop the brain. a b leptomenix salt gland salt gland } The Anatomy of Sea Turtles 125

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The Anatomy of Sea Turtles 126 NERVOUS SYSTEM Traditionally, the brain (Fig 189) is described by three regions that are initially demarked during development: the forebrain midbrain and hindbrain The following combinations of external and internal landmarks roughly identify these divisions. The forebrain extends from the nose to the posterior cerebrum. The midbrain extends from the eye to the posterior aspect of the optic lobes. Thehindbrain extends from the ear to the posterior cerebellum. These regions, in turn, are subdivided topographically and/or histochemically into principal divisions: telencephalon and diencephalon of the forebrain, mesencephalon of the midbrain, metencephalon and myelencephalon of the hindbrain (Fig. 189). Fig. 188. Parasagittal section of the brain and airways. The section though this green turtle head shows the tight epidural space and the more voluminous subdural space surrounding the brain. Because this cut is to the right of the midline, the cerebral ventricles and part of the cerebellar ventricle can be seen. The nasopharyngeal duct, part of the respiratory system, can be seen passing from the olfactory sacs to the internal choane.epidural space nasopharyngeal duct tele choroidea ventricle IV cerebral aqueduct cerebral spinal fluid

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NERVOUS SYSTEM cerebrum olfactory bulb olfactory nerve optic nerve optic lobe cerebellum ANTERIOR POSTERIOR spinal cord medulla telencephalon mesencephalon oculomotor nerve FOREBRAIN MIDBRAINHINDBRAIN myelencephalon metencephalon diencephalon Figs. 189a and 189b. Leatherback brain showing major regions and landmark structures. The brain is demarcated into its major regions and principal divisions. The divisions of the brain and their major components are as follows. Telencephalon: cranial nerve I, (olfactory nerve), olfactory bulbs, cerebral hemispheres, lateral ventricles. Diencephalon: hypothalamus, thalamus, infundibulum and pituitary, pineal, optic chiasma, cranial nerves II-III (optic and oculomotor nerves). Mesencephalon: optic lobes, third ventricle, cerebral aqueduct, cranial nerve IV (trochlear nerve). Metencephalon: cerebellum, anterior part of medulla, fourth ventricle, cranial nerves V-X (trigeminal, abducens, facial, statoaccoustic, glossopharyngeal, and vagus, respectively). Myelencephalon: most of medulla, cranial nerves XI-XII (spinal accessory and hypoglossal). a b The Anatomy of Sea Turtles 127

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The Anatomy of Sea Turtles 128 NERVOUS SYSTEM The brain forms as a tube during sea turtle development. It then undergoes considerable regional specialization, torsion, and expansion to form the structures found in adult turtles. Remnants of the nerve tube cavity persist as the lateral ventricles of the cerebral hemispheres, the third ventricle and cerebral aqueduct and the fourth ventricle of the cerebellum and medulla (Fig. 188). Most of the cranial nerves arise ventrally and laterally, and are easiest to observe when the brain is removed (Figs. 189-191). XI spinal accessory nerve XII hypoglossal nerve VI abducens nerve IX glossopharyngeal nerve V trigeminal nerve III oculomotor nerve II optic nerve infundibulum brain case VII facial & VIII statoacoustic root}X vagus nerve } Figs. 190a and 190b. Ventral surface of a ridley brain. This brain is viewed from the posterior aspect of the skull and is reflected anteriorly and dorsally. Only the optic and olfactory nerves are still attached to the head. The cut pituitary can be seen in the sella tursica in the floor of the brain case, while the infundibulum is removed with the rest of the brain.sella tursicaa b

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NERVOUS SYSTEM spinal cord cerebrum olfactory bulb optic nerves optic lobe trigeminal nerve cerebellum facial and statoaccoustic roots oculomotor nerve spinal accessory nerves medulla Figs. 191a and 191b. Ventrolateral view of a loggerhead brain without the olfactory nerves. The size of the brain of mature and maturing turtles is remarkably small for the body size. This brain from a 72 cm SCL loggerhead is just less than 10 cm long. Specific landmarks identifying the parts of the brain differ slightly across cheloniids and, even more when compared with Dermochelys (Figs. 192-202). Among the cheloniids, the brain is closest to the skull roof in Lepidochelys kempii It is furthest from the skull roof in adult Caretta caretta and Eretmochelys imbricata Scalation patterns on the lateral head and the position of the ear provide species-specific landmarks for some structures (Fig. 192). The brain of the leatherback is housed deeply, except for the pineal, which extends dorsally in a cartilaginous cone-like chamber adjacent to the pink spot on the middorsal surface of the head (Figs. 201-202). a b The Anatomy of Sea Turtles 129

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The Anatomy of Sea Turtles 130 NERVOUS SYSTEM Fig. 192. Brain landmarks for marine turtles. Overlays of brain positions are shown for 5 species. The position of the head scales, the eye, and the ear provide some reference points for identifying the position of the brain, which varies in dorsal-ventral position with species. The brain position of the leatherback, in this drawing, is based more upon the shape of the braincase because of the poor condition of all leatherback brains examined. The landmarks shown are accurate for large turtles, however the brains of hatchlings and juveniles are disproportionately larger. Caretta caretta Eretmochelys imbricata Chelonia mydas Lepidochelys kempi Dermochelys coriaceaa

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NERVOUS SYSTEM supraoccipital process cerebellum optic lobe pineal parietal cerebrum olfactory bulb olfactory nerve medulla tela choroidea frontal nasal olfactory sac interorbital septum optic nerve premaxilla rhamphotheca palatine dentary infundibulum & pituitary body of hyoid pterygoid trachea sphenoid esophagus tonguea b The Anatomy of Sea Turtles 131Figs. 193a and 193b. Parasagittal view of a loggerhead head. The brain, airways, oral cavity, and esophagus are exposed. The interorbital septum is intact and the optic nerve is seen passing through its foramen. There is a large subdural space, above the cerebrum and olfactory nerve, in loggerheads.

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The Anatomy of Sea Turtles 132 NERVOUS SYSTEM cerebellum optic lobe pineal cerebrum olfactory bulb olfactory nerve medulla tela choroidea olfactory sac infundibulum & pituitary dura mater dentary optic nerve cerebellar ventricle ventricle IV ventricle optic chiasma spinal cord Figs. 194a and 194b. Parasagittal cut through the head of a subadult loggerhead, close up. The positions of the brain, its parts, and the large subdural space containing cerebral spinal fluid relative to the dorsal skull are clear. The lateral ventricles are not exposed by this cut; the third ventricle and cerebral aqueduct are seen ventral to the optic lobe. The cerebellar ventricle is part of the 4th ventricle. Ventrally, the infundibulum leads to the pituitary (dorsal to the palate). The pituitary is housed in a bony socket, the sella tursica. a b

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NERVOUS SYSTEM tongue external nares nasopharyngeal duct olfactory sac interorbital septum olfactory bulb cerebrum optic lobe optic nerve optic peduncle cerebellum trachea rhamphotheca a b The Anatomy of Sea Turtles 133Figs. 195a and 195b. Parasagittal cut through an immature green turtle head. This view shows the spatial relationships of the CNS to other head structures. The brain is located close to the dorsal skull. The cut removed part of the interorbital septum so that the eye muscles are exposed dorsal to the palate and posterior to the olfactory sac. The intact olfactory nerve can be seen extending to the olfactory sac.

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The Anatomy of Sea Turtles 134 NERVOUS SYSTEM Figs. 196a and 196b. Parasagittal cut through a subadult green turtle head (close up). The brain is located very close to the dorsal skull in green turtles. The lateral ventricles are just exposed by the parasagittal cut; part of the cerebral aqueduct is seen within and ventral to the optic lobe. The cerebellar ventricle, part of the fourth ventricle, is exposed. glottis optic nerve mandible interorbital septum olfactory sac olfactory bulb cerebellum supraoccipital process IV ventricle tele choroidea cerebrum pineal optic lobe lateral ventricle spinal meninges a b

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NERVOUS SYSTEM medulla cerebellum optic lobe pineal optic nerve olfactory bulb cerebral hemisphere olfactory nerve olfactory sac interorbital septum maxilla premaxilla dentary glottis trachea esophagus tongue a b The Anatomy of Sea Turtles 135Figs. 197a and 197b. Parasagittal cut through the head of an immature Kemp’s ridley. The anterior half of the brain is flexed slightly dorsally in this species.

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The Anatomy of Sea Turtles 136 NERVOUS SYSTEM Figs. 198a and 198b. Parasagittal cut near the midline of a juvenile Kemp's ridley turtle (close up). The cerebral hemispheres are closer to the skull roof bones in ridleys than in the other cheloniid species. The cut was positioned so that the optic chiasma (at the posterior end of the optic nerve) was bifurcated. The pituitary is not seen in this section. medulla tela choroidea cerebellum optic lobe pineal optic nerve pterygoid carotid canalventricle cerebellar ventricle basioccipital occipital condyle atlas ventricle IV olfactory bulb cerebrum olfactory nerve olfactory sac interorbital septum maxilla glottis tongue a b

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NERVOUS SYSTEM supraoccipital crest pineal optic lobe medulla cerebellum cerebrum olfactory bulb olfactory nerve nasal sac trachea glottis esophagus optic nerve spinal meninges a b The Anatomy of Sea Turtles 137Figs. 199a and 199b. Parasagittal section through a hawksbill head. The brain is not as closely positioned to the skull roof in hawksbills as in other cheloniids. The pineal gland is clearly exposed in this dissection. Other parts of the brain are partially decomposed so their structure is slightly collapsed. The partial collapse makes the spinal meninges more distinct. The trachea and oral cavities are clearly exposed. The esophagus is collapsed in this specimen.

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The Anatomy of Sea Turtles 138 NERVOUS SYSTEM esophagus tongue glottis trachea hyoid pineal cerebellum cerebrum olfactory bulb olfactory nerve nasal sac optic nerve spinal cord medulla fourth ventricle Figs. 200a and 200b. Parasagittal cut near the midline of a subadult hawksbill turtle (close up). The subdural space is relatively large in the hawksbills. In this dissection, the medulla was sliced so a portion is displaced ventrally to an abnormal position. Structures from other systems are clearly exposed in this dissection. The tongue, glottis, and trachea are shown with the supporting hyoid skeletal structure. a b

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NERVOUS SYSTEM interorbital septum salt gland nasal sac cerebellum glottis palate premaxilla supraoccipital crest spinal cord covered with spinal meninges atlas trachea tongue axis cervical vertebra 3 oral papillae esophagus esophageal papillae body of hyoid olfactory nerve olfactory bulb cerebrum pineal optic lobe cartilaginous part of brain case a b The Anatomy of Sea Turtles 139Figs. 201a and 201b. Midsagittal section of an adult leatherback head. The braincase is largely cartilaginous around the dorsal and anterior aspects of the forebrain and midbrain. The parietal and frontal skull bones cover this cartilaginous portion of the braincase. The brain is partially decomposed and has collapsed. The extremely hypertrophied salt gland is visible where a portion extends medial to the eye.

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The Anatomy of Sea Turtles 140 NERVOUS SYSTEM medulla spinal meninges esophagus with papillae cerebellum optic lobe cartilage cerebrum pineal olfactory bulb olfactory nerve nasal sac optic nerve interorbital septum oral papillae tongue infundibulum (pituitary) salt gland Figs. 202a and 202b. A midsagittal cut of an adult leatherback head (close up). The brain is partially decomposed, however the pineal is still attached to the skull roof dorsally and the infundibulum remains attached to the pituitary ventrally. The largely cartilaginous positions of the braincase are typical of leatherbacks. a b

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NERVOUS SYSTEM The relative sizes of parts of the brain vary through ontogeny. The brain is proportionately larger in hatchlings and juveniles than in subadults and adults (Fig. 203). The olfactory nerves become proportionately longer and the cerebral hemispheres, optic lobes, and cerebellum are proportionately smaller in subadult and adult turtles. Peripheral Nerves -The spinal nerves form the peripheral nervous system They leave the spinal cord as paired dorsal and ventral nerve roots and exit the vertebrae via intervertebral foramina The dorsal nerves are composed of somatic and visceral sensory nerve fibers and may contain motor fibers as well; the ventral roots are generally composed of both somatic and visceral motor nerve fibers. These nerves function as the autonomic nervous system. The autonomic nervous system of turtles has both sympathetic and parasympathetic components. However, these are not anatomically segregated as "thoracolumbar" sympathetic and "craniosacral" parasympathetic regions as in mammals. Hence, nerves arising along the length of the spinal cord may have both sympathetic and parasympathetic components. Two networks of interconnected spinal nerves, the brachial plexus and sacral (= lumbosacral) plexus are associated with control of the limbs. They are poorly described in the literature on sea turtles. In cheloniids they are formed by ventral nerve roots and their branches. The brachial plexus (Figs. 204-206) arises at the level of cervical vertebrae VI-VIII in sea turtles. These cervical nerves form a complex network innervating the pectoral, arm (humerus), and flipper muscles (Table 1) as well as sending branches to the respiratory muscles. Most muscles receive innervation from more than one branch of the plexus. A ventral branch of nerve VI makes a large contribution to the median nerve. Nerves VII & VIII give rise to the inferior brachial nerve, which immediately divides to form the superficial radial nerve and the deep radial nerve to the anterior shoulder and dorsal flipper. Next, the supracoracoideus subscapular and ulnar nerves arise and travel to those pectoral muscles and the ventral side of the flipper. The deltoideus nerve arises primarily from nerves (VI and VII). There are no descriptions available for the brachial and sacral plexuses of Dermochelys Fig. 203. Dorsal views of the brains of hatchling and juvenile turtles shows the negative allometric growth of the brain relative to the size of the head. Hatchlings have disproportionately large brains. The Anatomy of Sea Turtles 141

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Fig. 204. The brachial plexus of a hawksbill. The brachial plexus arises from the most posterior cervical vertebrae. Its nerves innervate the pectoral muscles and flippers. The carapace and connective tissues have been removed to provide this posterodorsal view of the brachial plexus. Its 3 rami arise from the intervertebral foramina and immediately undergo a series of divisions and interconnections to form the nerves of the brachial plexus. NERVOUS SYSTEM The Anatomy of Sea Turtles 142 deep radial nerve supracoracoideus nerve subscapular nerve VIII VII VI inferior brachialis nerve subscapularis muscle coracobrachialis nerve ventral nerve VII deltoideus nerve triceps humeral head ulnar nerve tractor radii muscle pectoralis major muscle inferior brachial nerve deltoideus muscleFig. 205. Branch of the brachial plexus of a hawksbill (ventral view). The inferior brachial nerve of the brachial plexus travels along the ventral and anterior aspect of the flipper. The ulnar nerve is seen branching off. The other main nerve of the arm, the median nerve, is deep to the inferior brachial nerve and cannot be seen.

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NERVOUS SYSTEM Fig. 206. Diagram of the right brachial plexus based upon cheloniids. The three roots of the brachial plexus and their interconnections to the flipper and shoulder musculature are shown. Branches to ventral muscles go to the pectoralis, biceps superficialis, biceps profundus, and the deltoideus Larger branches are shown as thicker lines. The most distal branches are not shown. The Anatomy of Sea Turtles 143The sacral plexus (Figs. 207-208) arises as 4 (sometimes 5-6) rami (branches) from spinal nerves XVII-XXI, located on the last dorsal and sacral vertebrae. These nerves interconnect and subdivide several times as they send nerves to the inguinal, pelvic, and hind leg muscles (Table 1). Many muscles receive multiple innervations. The more posterior nerves roots give rise to the obturator nerve, going to the ventral pelvic muscles, and the ichiadicus nerve, which runs medial to the ilium and then divides to form the peroneal and sciatic nerves. The anterior two nerve roots interconnect provide major innervations (via crural femoral and tibial nerves) to the inguinal muscles, thigh adductors, and leg extensors. to anterior shoulder to radial side of flipper to ulnar side of flipper to humerus to coracobrachialis to respiratory muscles VI VIIVIII to ventral muscles} } to subscapularis

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NERVOUS SYSTEM sciatic nerve iliofemoralis muscle iliofibularis muscle (cut)femorotibialis (cut)peroneal nerve ambiens muscle obturator nerve femoral nerve crural nerves tibial nerve tail XX IXX XVII XVIIIFig. 208. Diagram of the right sacral plexus (lateral view) based upon cheloniids. The roots of the sacral plexus and their interconnections to the pelvic, inguinal, and hind limb musculature are diagrammed. Thicker lines represent larger branches. The most distal branches are not shown. The lone branch medial to the ilium is the oburator nerve to the ventral pelvic muscles. The Anatomy of Sea Turtles 144 Fig. 207. The sacral plexus of a hawksbill. This lateral view of the sacral plexus shows four roots giving rise to the interconnecting nerves that innervate the hind limb and respiratory muscles of the inguinal region. The most posterior branch of the sacral plexus extends posteriorly, medial to the ilium, and then travels along the posterior hind limb. It gives rise to the sciatic, tibial and peroneal nerves that innervate many of the distal hind limb muscles. ilium XXI XX IXX XXVIII XXVII to posterior foot to ventral foot to posterior leg & leg flexors to anterodorsal lower leg to dorsal & anterior thigh to inguinal & thigh muscles to inguinal muscles }

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NERVOUS SYSTEM Brachial PlexusInnervations Inferior brachial nerveTractor radii Superficial radial nerveLatissimus dorsi Deep radial nerveLatissimus dorsi Supracoracoideus Testoscapularis Supracoracoideus nerveSupracoracoideus Pectoralis major Biceps brachii (profundus and superficialis) Subscapular nerveSubscapularis Axillary (= Deltoideus) nerveDeltoideus (ventral parts) Brachialis Radial nerveLatissimus dorsi Teres major Tractor radii Triceps brachii (humeral head) Respiratory muscles Ulnar nerveDeltoideus (dorsal head) Latissimus dorsi Subscapularis Extensor radialis Medial flipper muscles Extensors of digits Median nerveCoracobrachialis Flexor carpi ulnaris Flexors of digits Sacral Plexus Innervations Crural nerveInguinal muscles Thigh protractors (Triceps femoris complex) Femoral nervePuboischiofemoralis Dorsal hip muscles Obturator nerveVentral hip muscles Caudi-ilioformoralis Ischiotrocantericus Adductor femoris Flexor tibialis (internus & externus) Pubotibialis complex Ischiadicus nervePosterodorsal hip muscles Sciatic nerveGastrocnemius Iliofemoralis Ventrolateral foot extensors Peroneal nerveTriceps femoris (ambiens, femorotibialis, Iliotibialis) Gastrocnemius Foot flexors Tibial nerveFlexor tibialis (internus & externus) Ambiens Pubotibialis Inguinal muscles Foot extensorsTable 1. Major innervations by the nerves of the brachial and sacral plexuses. Nerves are named using mammalian nerve terminology. The Anatomy of Sea Turtles 145

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The Anatomy of Sea Turtles 146 SENSE ORGANS Sense OrgansChemical, visual, acoustic, and vestibular senses of sea turtles are concentrated in the head. The tongue (Fig. 209) is a muscular organ covered by a mucous membrane. Taste buds are present but are poorly characterized. The tongue lacks obvious lymphoid tissue at its posterior, as is seen in mammals. The nose includes external nares leading to an olfactory(nasal) sacs The olfactory sac communicates via the nasopharyngeal duct to the internal choanae (internal nares; Figs. 195 and 210). The olfactory sacs and choanal folds are covered with a ciliated sensory epithelium. The olfactory epithelium, located posterodorsally in the nasal cavity, is innervated by the olfactory nerve leading to the olfactory bulb (Figs. 189, 193-201). The vomeronasal organ (Jacobsen's organ) of turtles is not typical in its structure. This specialized sense organ, usually associated with detection of airborne and substrate-borne odor molecules, is not recessed in a separate pit as in snakes and some lizards. It is widely distributed anterolaterally and ventrally in the olfactory sac. The vomeronasal organ is distinguished from olfactory epithelium by region and histological characteristics rather than gross appearance. It is innervated by nerves running to Fig. 210. The sense organs of a green turtle. The nares lead to large pigmented olfactory sacks. There are several choanal folds on the walls of the olfactory sac, which lack bony supports. The olfactory sac leads, via the nasopharyngeal duct to the internal choanae. The olfactory nerve is cut in this dissection and has fallen ventrally. The inner cavity is cut ventral to the brain; the cochlea is also cut and part is exposed at the ends of the inner ear pointers. The middle ear is located more laterally and hence is not seen in this view.inner ear nasopharyngeal duct salt gland olfactory sac nares eye(medial view) Fig. 209. Dorsal view of the tongue of the Kemp's ridley. The tongue is muscular and attached to the floor of the mouth. The surface is grossly smooth. The epithelium is covered in small, short, flat papillae.glottis

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SENSE ORGANS the accessory olfactory bulb (effectively the dorsal part of what is grossly called the olfactory bulb). A series of small spike-like papillae line the lateral margin of the internal choane in C. mydas These papillae are absent or poorly developed in other species. The anterior tissue lining the nares is highly vascular and erectile in adult sea turtles. It appears not to have a sensory function but instead has the ability to seal the nostrils when the turtles are submerged. The eyes of sea turtles are round and housed in bony orbits. The eye is protected by dorsal and ventral lids The ventral lid is continuous with the conjunctiva which forms its inner surface. The nictitating membrane at the anterior and ventral corner of the eye, also is continuous with the conjunctiva (Figs. 198-200). iris palpebral scales dorsal lid secondary lid ventral lid nictitating membrane pupil sclera Figs. 211a and 211b. Eye and lids of a loggerhead. The eyes are located dorsally and anterolaterally. They have overlapping fields of view (hence, binocular vision). The dorsal and ventral lids are keratinized and mobile. The secondary lid is also keratinized but not mobile. The cornea, not labeled, is a clear portion of the sclera that overlies the iris and pupil. Palpebral scales are found in the margins of the ventral lid in cheloniids, but not in Dermochelys. The Anatomy of Sea Turtles 147a b

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The Anatomy of Sea Turtles 148 SENSE ORGANS Figs. 212a and 212b. Leatherback eye. The lids of the leatherback eyes are positioned as more anterior and posterior lids than dorsal and ventral lids. sclera iris pupil nictitating membrane posterior (ventral) lidexternal naresexternal nares anterior (dorsal) lid

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Fig. 213. Leatherback eye dissection. The lids of this leatherback eye were removed to show the extent and position of the nictitating membrane. sclera iris conjunctiva(cut)external nares nictitating membrane conjunctiva(cut) SENSE ORGANS The Anatomy of Sea Turtles 149

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The Anatomy of Sea Turtles 150 SENSE ORGANS The wall of the eye (or globe) is composed of 3 major layers: the sclera, uvea, and retina surrounding the viscous vitreous body The eye is supported medially by cartilage and laterally by scleral ossicles (Figs. 82-84). The outer-most layer is the sclera The eye muscles attach to the sclera (Figs. 215-216). The superior oblique muscle inserts dorsally and it is innervated by the trochlear nerve The superior rectus muscle attaches posteriorly. Ventral to these muscles is the attachment of the internal rectus muscle. Anteriorly, the pyramidalis muscle extends from the eye to the eyelids and nictitating membrane. Deep and ventral to the pyramidalis muscle are the inferior oblique and inferior rectus muscles. The external rectus muscle is located posteriorly and ventrally and is innervated by the abducens nerve The superior rectus, inferior rectus, inferior oblique and internal rectus muscles are all innervated by the oculomotor nerve Fig. 214. Sagittal section of a loggerhead eye. The eye is cut into medial and lateral halves. The retina and back of the eye are on the left. The inside of the iris, lens, and pupil are in the middle of the photo. Part of the vitreous body was removed and placed on the right. Fig. 215. Lateral view of a loggerhead left eye. The extrinsic eye muscles are extended radially in this picture to show their relative insertion points. Normally their origins would converge on the interorbital septum. retina sclera iris vitreous body(cut)lens coroid(of uvea)superior oblique Harderian gland medial rectus ANTERIOR DORSAL superior rectus lateral rectus external rectus salt gland(cut)inferior oblique

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SENSE ORGANS The sclera, often termed the "white of the eye" in vertebrates, is partially pigmented in most sea turtles. The sclera is clear at the front of the eye; there it is termed the cornea Internal to the sclera is the uvea, composed of the choroid, tapetum lucidum, ciliary body and the iris (Fig. 199). The choroid is pigmented and extends from the iris to the retina. It includes the reflective material (tapetum lucidum) that is responsible for "eye-shine”. The reflective material enhances the eye's sensitivity under low light conditions. The ciliary body (not shown), is responsible for changing lens shape during visual accommodation. It extends from the choroid near the front of the eye, to the attachments that suspend the lens. The iris is pigmented brown or black and extends from the choroid across the front of the eye. The limbus (= limbas) is the tissue between the cornea and the sclera. Because the cornea and sclera are continuous with one another, the limbus represents a transitional zone that is usually described histologically (not labeled in the figures). The free border of the iris forms the edge of the pupil The lens is strongly curved in sea turtles (Fig. 214). It is suspended behind the pupil and iris by "ligaments" attached to striated muscles of the ciliary bodies. The chamber of the eye is filled with a clear viscous liquid, the vitreous body The eyes are photoreceptors that are capable of color and shape discrimination. The retina is the sensory layer of the eye; it detects color as well as brightness. The retina is composed of several cell layers and includes several types of rods and cones, each containing photopigments. The ears of sea turtles are responsible for hearing and equilibrium. Each ear consists of an external tympanum covered by a tympanic scale that stretches across the otic notch (= auditory canal) formed by the quadrate, quadratojugal and squamosal bones (Fig. 28). There is middle and inner ear but no outer ear. The middle ear is involved in sound transduction while the inner ear functions in sound reception and the detection of Fig. 216. Loggerhead left eye (medial view) showing extrinsic eye muscles. The extrinsic eye muscles are responsible for eye movements. Also shown is the Harderian gland, which lubricates the eye and a portion of the salt gland (an organ primarily responsible for salt excretion and maintaining water balance). The retractor muscle surrounds the optic nerve and positions the eye deeply or shallowly in the orbit. lateral rectus superior rectus superior oblique optic nerve Harderian gland medial rectus external rectus retractor muscle salt gland(cut)inferior oblique ANTERIOR DORSAL The Anatomy of Sea Turtles 151

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The Anatomy of Sea Turtles 152 position and acceleration. The middle ear contains a single ear bone, the stapes (= columella). The stapes extends from the tympanum via an extrastapedial process of cartilage (Fig. 217), through the tympanic cavity and recessus cavi tympani to articulate via an expanded footplate (also cartilage) on the vestibular window of the cochlea (Fig. 218). A Eustachian tube extends to each middle ear from the mouth near the jaw joints (Fig. 165). The inner ear of turtles is composed of the cochlea and 3 semicircular canals, all of which are encased in bone. The cochlea is involved in sound transduction and is innervated by the auditory nerve; it transmits sound information to the brain. The semicircular canals sense the head's position and movement by detecting changes in acceleration in the three planes. One canal resides in each plane (sagittal, coronal, and axial) in each ear. Fig. 217. The tympanum of a ridley ear. The tympanic scale has been removed to expose the tympanum and the distal-most aspect of the extrastapedial process (at arrow). Fig. 218. Ventral view of a ridley ear. The coronal section exposes the tympanic cavity (= the otic notch of a skull) and, more medially the recessus cavi tympani. The footplate of the stapes articulates with the vestibular window. SENSE ORGANS tympanum stapes tympanic cavity brain cochlea recessus cavi tympani

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UROGENITAL SYSTEM Urogenital AnatomyThe urogenital system (UG) is made up of the kidneys ureters gonads and their ducts, the urinary bladder and derivatives of the genital papilla (penis or clitoris) in the floor of the cloaca. The kidneys function in removal of nitrogenous wastes (excretion) and maintaining water and electrolyte balance (osmoregulation). The ureters transport nitrogenous wastes to the cloaca where it either drains into the urinary bladder or is eliminated. The gonads ( ovaries or testes ) produce gametes and their ducts transmit eggs or sperm to the cloaca. They are reproductive structures. The urinary bladder functions in water and urine storage. The cloaca is the common chamber into which the ureters, gonadal ducts, rectum, and bladder empty. The cloaca leads to the outside of the body via the vent. Excretory System. The kidneys are paired, lobular, elliptical red structures that are located retroperitoneally (between the peritoneum and the shell). Sea turtle kidneys are metanephric meaning (1) they arise from the posterior part of the nephric ridge in the embryo and (2) the kidney tubules are drained by ureters (metanephric ducts). The ureters extend from the kidney, through the peritoneum and empty into the dorsal cloaca on each side. Ureters are located on the ventral surface of each kidney. They drain uric acid, ammonia, and water to the cloaca. Each ureter enters the cloaca with a gonadal duct via a urogenital papilla in the urodeum portion of the cloaca (Figs. 219 220). Fig. 219. Diagram of the Urogenital System. The relative positions of the kidneys, gonads (undifferentieted for diagrammatic purposes), accessory ducts, urinary bladder, rectum and cloaca are shown. Anterior is to the left. The Anatomy of Sea Turtles 153 gonadal duct urinary bladder plastron anus urodeum urogenital papilla rectum carapace kidney ureter cloaca genital papilla vent tail accessory urinary bladder gonad lung

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UROGENITAL SYSTEM Fig. 220. Lateral view of the cloaca of an immature hawksbill. The lateral wall of the cloaca has been cut away to show the urogenital papillae from the oviducts and ureters, the opening to the urinary bladder, and the dorsally positioned anus from the rectum. The urinary and genital ducts enter the cloaca adjacent to one another in females. They are small and located as the lateral walls of the urogenital papillae. The kidneys of sea turtles lack a distinct cortex and medulla Sea turtle nephrons are composed of a renal capsule proximal tubule (which is linked to water transport and protein synthesis), an intermediate segment (function unknown), distal convoluted tubule (responsible for fluid reabsorption) and collecting tubule (draining to the ureters). There is no loop of Henle as is found in mammalian nephrons. Unlike higher vertebrates, marine turtles retain the ability to form new functional nephrons as they mature (and perhaps throughout life). Blood flows through the kidneys from afferent vessels entering (renal arteries and iliac veins), and efferent vessels leaving (renal portal and renal veins) the kidneys. Water and mineral waste (a filtrate) is removed from the blood at the renal corpuscle (glomerulus plus renal capsule). The urinary bladder is a highly elastic, single, sack-like structure located along the midline of the pelvis. It opens via a single opening to the ventral floor of the cloaca (Figs. 219-221). The bladder is located ventrally and urine, water, and sometimes other waste products may enter it via the cloaca. This anatomical position and the connection of the cloaca to the outside sometimes allows materials other than urine (e.g., fecal material, parasites, or, in females, eggs) to enter opportunistically. Sea turtles have two small accessory urinary bladders connected to the urinary bladder; each located lateral to the neck of the urinary bladder and dorsal to the pubis (Fig. 221). They are seldom filled and often are missed in dissections. Gonads. The gonads of both species are located dorsally in the body cavity, posterior to the lungs, and ventral to the kidneys and peritoneal wall Figs. 222 and 223). clitoris anus urogenital papilla neck of urinary bladder kidney The Anatomy of Sea Turtles 154 POSTERIOR

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UROGENITAL SYSTEM Fig. 221. Dorsal view of the urinary bladder and dorsal pelvis of a male loggerhead. The empty urinary bladder and accessory bladders are shown free of connective tissues. The ilia are found laterally; the sacral and proximal caudal vertebrae are present dorsally. The sacral plexus is exposed in part. pubis tail urinary bladder sacral plexus accessory urinary bladder The Anatomy of Sea Turtles 155 Figs. 222a and 222b. Testes of an immature green turtle. The testes are attached to the peritoneal wall by their flat dorsal surface. Lateral and slightly dorsal to each testes is an epididymis, which leads to a vas deferens. The surface of the testis is smooth in immature turtles. lung dorsal aorta epididymis mesorchium testes vas deferens a b

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immature oviduct mesotubarium mesovarium immature ovary dorsal aorta lung Figs. 223a and 223b. Ovaries of an immature green turtle. The ovaries are attached to the peritoneal wall by their lateral edges. The surface of the ovary is granular. Lateral to the ovary is the immature oviduct, which is suspended by the mesotubarium. The Anatomy of Sea Turtles 156 UROGENITAL SYSTEM Female: The female reproductive tract consists of paired ovaries, oviducts (also called Mllerian ducts ), and the suspensory ligaments or mesenteries (mesovarium mesosalpinx and mesotubarium ). The ovary and oviduct change in size and composition with age and between breeding and nonbreeding seasons. The cranial pole of the ovary is located just posterior to the lung and extends posteromedially toward the cloaca. Along its medial and dorsal surface, it is attached by the mesovarium to the peritoneum that overlies the kidney (Fig. 224) Another ligament, the mesotubarium, extends from the ovary to the oviduct. The oviduct lies lateral to the ovary and extends anteriorly, before curving medially and ending in a funnel shaped opening, the ostium. The ostium, which receives ovulated follicles, is supported by the mesosalpinx. There are no tubules connecting the ovary directly to the oviduct. The posterior end of each oviduct joins the urodeum of the cloaca (Fig. 225). a b

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Figs. 224a and 224b. Ovary and accessory ducts of a juvenile green turtle, (ventral view). This immature ovary has a granular surface. Its follicles have not yet added significant amounts of yolk. The immature oviduct is a thin, flat tube supported in the mesentery (mesotubarium). Engorged renal arteries and veins can be seen extending from the kidney, anatomically dorsal to the ovary, and toward the midline. The Anatomy of Sea Turtles 157 UROGENITAL SYSTEM right lung liver right lobe renal arteries and vein kidney ovary immature oviduct pelvis mesotubarium a b

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The Anatomy of Sea Turtles 158 UROGENITAL SYSTEM peritoneum immature oviducts colon(cut) right lung left lung pelvis(reflected posteriorly and ventrally)ovaries urinary bladder Figs. 225a and 225b. Immature ovary and oviduct (ventral view). The immature ovary is thin and located more medially than the oviduct. The immature oviduct extends anteriorly then turns posteriorly. The ostium is formed at the expanded end. The oviduct, mesotubarium, and mesosalpinx are reflected laterally. a b

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In hatchlings, the ovaries are difficult to distinguish from testes. If histology is unavailable, the attachment of the mesovarium to the ovary edge and the lack of a coiled vas deferens suggest that the gonad is an ovary. In older turtles, the gonad will be pink and will have a grainy texture as small follicles become more distinct. As turtles approach maturity, some follicles increase in size and start to accumulate bright yellow yolk. In sexually mature turtles, mature follicles tend to cluster along the cranial aspect of the ovaries. Immature follicles are most concentrated in the posterior third of the ovary. Mature turtles that have nested previously will have large follicles that are ~2-3cm in diameter and scars from previously ovulated follicles, corpora albicans (Fig. 226). Recently ovulated follicles leave active scars, each is called a corpus luteum The corpus luteum becomes a corpus albicans after it ceases to produce the hormone progesterone. The ages of corpora albicans are difficult to judge, however larger ones are generally more recent than smaller ones. It is safest to use this information simply to determine if the turtle had nested previously or not. The Anatomy of Sea Turtles 159 UROGENITAL SYSTEM oviduct with shelled eggs corpora albicans mature & maturing folicles shelled eggs Figs. 226a and 226b. Eggs, follicles, and corpora albicans in a reproductively active loggerhead. This oviduct holds shelled eggs. Above the oviduct are several sizes of maturing follicles and the scars (corpora albicans) remaining from the sites of ovulated follicles. a b

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The oviduct of immature turtles is a thin walled tube (Figs. 224-225). As females mature, the walls of the oviduct thicken and the lumen increases in diameter. It appears folded along its length when not active (Fig. 227). The oviduct can be described functionally (but not in gross structure) as having 5 regions: the ostium (or infundibulum), aglandular segment, magnum, shell gland, and vagina. The ostium remains thin-walled but increases in size (Figs. 228-229). The oviduct of mature females is muscular and mobile. It is assumed that the ostium migrates across the ovary surface collecting the ovulated follicles. The Anatomy of Sea Turtles 160 UROGENITAL SYSTEM distaloviduct urodeum mesotubarium proximal oviduct Figs. 227a and 227b. Mature oviduct of a leatherback. The mature oviduct has a large lumen and the walls have undulatory folds. The mesosalpinx and mesotubarium enlarge to accommodate the mature structures. The distal ends would normally enter the cloaca. The proximal end is the site of the ostium. a b

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UROGENITAL SYSTEM Figs. 228a and 228b. The ostium of an immature oviduct. The ostium is flattened when not active; the funnel-shaped opening is small in young turtles. The Anatomy of Sea Turtles 161 mesosalpinx ostium immature oviduct uterine veins a b

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The Anatomy of Sea Turtles 162 UROGENITAL SYSTEM ostium of mature oviduct Figs. 229a and 229b. The ostium of a mature oviduct. The ostium of this leatherback's oviduct is large, funnel-shaped and thin walled. The base of the ostium opens into the aglandular part of the proximal oviduct. In preparation for nesting, an entire clutch of follicles matures and ovulates together. Once in the ostium, each follicle travels past the aglandular segment and into the magnum (anterior glandular region) where it is coated with layers of albumen. After about 3 days, the follicles pass to the shell gland where the protein and carbohydrate shell membrane (chorion) and the aragonite shell matrix are secreted. The shell calcification takes about 6 to 7 days. Eggs pass to the vagina where they remain until deposition, several days later. During deposition, the posterior oviduct allows eggs to pass to the cloaca, then out the vent into the nest. The cloaca forms a tubular orifice in nesting turtles. The structures that form this "egg tube" are unknown. Males : The male reproductive tract consists of paired testes epididymi deferent ducts (vas deferens = ductus deferens), suspensory ligaments ( mesorchium from the body wall to the testis), and a single penis Mllerian ducts may persist as a pair of small, flat, thin-walled tubes in some males. When present, they are located along the lateral body wall (suspended by a mesotubarium) from the duct to the testis or peritoneum overlying the kidney. They will often extend toward the anterior third of the body, lateral to the lung. The testis is fusiform shaped (Fig. 222). The cranial pole is located just posterior to the lung; it extends posteromedially toward the cloaca. Along its dorsal surface, it is attached by the mesorchium to the peritoneum overlying the kidney. The testis is light tan or yellow in some species and gray to pink in others. Sperm are produced in the testis and are conveyed via very small efferent ductules to the epididymis, which lies lateral or posterolateral to the testis. The vas deferens leads from the epididymis to the cloaca at the base of the penis, demarked by the corpra cavernosum (Fig. 222). The testis, epididymis, and vas deferens change in size and form with age and between a b

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breeding and nonbreeding seasons (Fig. 230). Testes in mature breeding males are often twice as long as their diameter and filled with white fluid (sperm and accessory gland fluid). The genital papilla elongates into the penis during maturation. The penis is retracted except during mating, trauma, or death; it lies in the ventral floor of the cloaca. It is composed of a pair of corpora cavernosa and a urethral groove (= sulcus spermaticus; Fig. 231). During mating, the corpora cavernosa are supplied with blood via the hypogastric and internal iliac veins. When erect, the walls of the urethral groove meet dorsally to form a functional tube through which sperm and fluids pass. Some species have ornamented structures (e.g., spines or flaps that have a triradiate form) on or near the glans penis at the distal tip (Fig. 232). Fig. 230. Mature loggerhead testis and accessory ducts (posteroventral view). The testes, epididymis, and vas deferens in a mature male during breeding season. The vas deferens lead to the base of the penis in the ventral floor of the cloaca. Fig. 231. Adult loggerhead penis (dorsal view). The marine turtle penis is part of the ventral floor of the cloaca. The two corpora cavernosa function in penile erection and elongation. The urethral groove, between the two cavernous bodies conveys sperm during mating. The penis is completely housed within the cloaca when not erect. UROGENITAL SYSTEM The Anatomy of Sea Turtles 163 vas deferens epididymis cloaca rectum glans penis urethral groove corpus cavernosum cloacal floor and musculature

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The Anatomy of Sea Turtles 164 UROGENITAL SYSTEM Fig. 232. Tail and penis of a Kemp's ridley. The long tail and distally positioned vent are distinctive of adult male turtles. This animal has a semi-erect penis with a subterminal horn on the ventral lobe of the glans penis. Not all species have ornaments on the penis. Generally, maturing males have a more distally positioned vent than a female of the same body size. However, not all males start maturation at the same size, so the combination of tail length and cloacal position should be used with caution when identifying the sex of the turtle. Fig. 233. Tail of an adult female Kemp's ridley. The short tail and cloaca located proximally are characteristic of females and immature males. This female protruded the cloacal opening as is seen in nesting turtles.

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UROGENITAL SYSTEM Fig. 234. Sexually mature male ridley. Male sexually dimorphic characteristics include an elongated tail, long curved claws, and, during breeding season, the midventral plastron becomes soft. The Anatomy of Sea Turtles 165 Sexual dimorphism. Adult females differ little in external morphology from large, immature males. Typically, females have a short tail and the cloacal opening ( vent ) is located roughly half way between the tip of the tail and the plastron's anal scute (Fig. 232). Within the cloaca, the genital papilla remains small as the clitoris on the floor of the cloaca. (Fig. 219). In the Western North Atlantic, female loggerheads mature at an average SCL of 92 cm (range: 75-104 cm). Green turtle females mature and nest at an average SCL of 97 cm (range: 83-113 cm) and leatherback females are about 155 cm CCL (very few nesting females have been measured on U.S. beaches). The minimum size of a nesting female leatherback in the USVI was 133 cm CCL. Adult males are characterized by a long tail with the cloacal opening near the tip, and strongly curved claws on the second digit. During breeding season, a decornification of the plastron occurs along and to each side of the midline (Fig. 233). The plastron becomes increasingly vascular and edematous. Male leatherbacks, have slightly concave plastrons. There is no evidence of decornification or increased plastral vascularization during leatherback breeding season.

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SELECTED BIBLIOGRAPHY Ashley, L. M. 1955. Laboratory Anatomy of the Turtle Wm. C. Brown Company Publishers. Dubuque, Iowa. 48 pp. Barragan, A.R. 1996. Anatomical basis for an intracardiac bloodflow model in sea turtles. pp. 34-37. In: Proceedings of the 15th Annual Symposium on Sea Turtle Biology and Conservation. pp. J. Keinath, D. E. Barnard, J. A. Musick, and B. A. Bell, Compilers. NOAA Technical Memorandum NMFSSEFSC-387. 355 pp. Baur, G. 1891. The pelvis of the testudinata, with notes on the evolution of the pelvis in general. 4(3, 6 February): 345-359. (Clark University). Beck, K., Loomis, M., Lewbart, G., Spelman, L., and Papich, M. 1995. Preliminary comparison of plasma concentrations of gentamicin injected into the cranial and caudal limb musculature of the eastern box turtle ( Terrapene carolina carolina ). Journal of Zoo and Wildlife Medicine 26(2):265-268. Bellairs, A. d' A. 1960. Reptiles. Life History, Evolution and Structure Harper Torchbooks/ The Science Library. Harper & Brothers. New York. 192 pp. Bojanus, L. H. 1970. Anatomie Testudinis Europaeae Facsimile Reprints in Herpetology. 26. C. Gans, I. S. Darevsky, and K. Adler, eds. SSAR. Bracegirdle, B. and P. H. Miles. 1978. An Atlas of Chordate Structure Heinemann Educational Books Ltd. The University Press. Oxford. 119 pp. Bruner, H. L. 1907/1908. On the cephalic veins and sinuses of reptiles, with description of a mechanism for raising the venous blood-pressure in the head. American Journal of Anatomy. VII: 1-117. Burggren, W., W. Mogens, L. Glass, and K. Johansen. 1977. Pulmonary ventilation: perfusion relationships in terrestrial and aquatic chelonian reptiles. Canadian Journal of Zoology. 55(12): 2024-2034. Burne, B. A. 1905. Notes on the muscular and visceral anatomy of the leathery turtle ( Dermochelys coriacea ). Proceedings of the Zoological Society of London. 1905: 291-324. Callister, R. J., R. Callister, and E. H. Peterson. 1989. Histochemical classification of neck and limb muscle fibers in a turtle, Pseudemys scripta : a study using microphotometry and cluster analysis techniques. Journal of Morphology. 199: 269-286. Davenport, J. and C. R. Scott. 1993. Individual growth and allometry of young green turtles ( Chelonia mydas L.). Herpetological Journal. 3:19-25. Deraniyagala, P.E.P. 1939. The Tetrapod Reptiles of Ceylon Ceylon Journal of Science, (Colombo Museum Natural History Series). 1:1-412. Detwiler, Samuel R. 1943. Vertebrate Photoreceptors The MacMillan Company, New York: 175 pp. Duncker, H. R. 1978. General morphology principles of amniote lungs. pp. 1-15. In: Respiratory Function in Birds, Adult and Embryonic J. Piiper, ed. Springer-Verlag, New York. Eckert, K. L., K. A. Bjorndal, F. A. Abreu-Grobois, and M. Donnelly (Editors). 1999. Research and management techniques for the conservation of sea turtles. IUCN/SSC Marine Turtle Specialist Group Publication No. 4. Edgeworth, F. H. 1935. The Cranial Muscles of Vertebrates The University Press. Cambridge. 493 pp. Ehrhart, L. M. and B. E. Witherington. 1986. Human and natural causes of marine turtle nest and hatchling mortality and their relationship to hatchling production on an important Florida nesting beach. Florida Game and Freshwater Fish Commission Tech Report No. 1:1-141. Evans, H. E. 1995. Anatomy of Reptiles World Veterinary Congress. Japanese Association of Veterinary Anatomy. WVA/WSAVA, Yokohama, Japan. Evans, Howard E. 1986. Reptiles. Introduction and anatomy. Chapter 13. In: Zoo and Wild Animal Medicine pp.108-132. 2nd edition. M. E. Fowler, ed. W. B. Saunders Company. Philadelphia. 617 pp. Ewert, M. A. 1985. Embryology of Turtles. pp. 75-267. In: Biology of the Reptilia Vol. 14 (Development A), C. Gans, F. Billett, and P.F. A. Maderson. eds. Academic Press. New York. 763 pp. Farrell, A. P., A. K. Gamperl, and E. T. B. Fransis. 1998. Comparative aspects of heart morphology. pp. 375-424. In: Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt, eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca. 660 pp. Fleetwood, J. N. and J. F. Munnell. 1996. Morphology of the airways and lung parenchyma in hatchlings of the loggerhead sea turtle, Caretta caretta Journal of Morphology. 227:289-304. Fox, H. 1977. The urogenital system of reptiles. Chapter 1. pp 1157. In: Biology of the Reptilia Vol. 6. (Morphology E). C. Gans and T. Parsons, eds. Academic Press. New York. 505 pp. Gaffney, E. S. 1972. An illustrated glossary of turtle skull nomenclature. American Museum Novitates. 2486, (9 May): 1-33. Gans, C. and G. M. Hughes. 1967. The mechanism of lung ventilation in the tortoise Testudo graeca Linn. Journal of Experimental Biology. 47(1):1-20. Gaunt, A. S. and C. Gans. 1969. Mechanics of respiration in the snapping turtle, Chelydra serpentina (Linn). Journal of Morphology. 128:195-228. The Anatomy of Sea Turtles 166

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SELECTED BIBLIOGRAPHY Gegenbaur, C. 1878. Elements of Comparative Anatomy 2nd ed. (Translated by F. J. Bell and E. R. Lankester). MacMillan and Company. London. 624 pp. Grasse, P. P. 1948. Reptiles. Vol. 14. Trait de Zoologie; anatomie systmatique, biologie Masson Publ., Paris. 836 pp. Hicks, J.W. 1998. Cardiac shunting in reptiles: mechanisms, regulation, and physiological functions. pp. 425-483. In, Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt, eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca. 660 pp. Hoffman, C. K. 1890. Reptilien. I. Schildkrten. In: Klassen und Ordnugen des Thier-Reichs. H. G. Bronn, ed. 6. (3):1-442. Holtz, P., K. Barker, G. J. Crawshaw, and H. Dobson, 1997. The anatomy and perfusion of the renal portal system in the red-eared slider ( Trachemys scripta elegans ). Journal of Zoo and Wildlife Medicine. 28(4):378-385. Holtz, P., I. K. Barker, J. P. Burger, G. J. Crawshaw, and P. D. Conlon. 1997. The anatomy and perfusion of the renal portal system in the red-eared slider ( Trachemys scripta elegans ). Journal of Zoo and Wildlife Medicine. 28(4):386-393. Hyman, L. H. 1979. Hyman's Comparative Vertebrate Anatomy M. H. Wake, ed. University of Chicago Press. Chicago. 788 pp. Jones, C. L. 1979. The morphology of the thigh of the mouse with special reference to tetrapod muscle homologies. Journal of Morphology. 162:275-310. Kardong, K. V. 2001. Vertebrates: Comparative Anatomy, Function, and Evolution 3rd Edition. McGraw-Hill. New York. 762 pp. Kuratani, S. 1989. Development of the orbital region in the chondrocranium of Caretta caretta Reconsideration of the vertebrate neurocranium configuration. Anatomisher Anzeiger (Jena). Bd. 169(5): 335-349. Lenhardt, M., R.C. Klinger, and J.A. Musick. 1985. Marine turtle middle-ear anatomy. Journal of Auditory Research. 25:66-72. Lloyd, M. and P. Morris. 1999. Chelonian venipuncture techniques. Bulletin of the Association of Reptilian and Amphibian Veterinarians. 9(1):26-29. Lnnberg, E. 1902. On some points of relation between the morphological structure of the intestine and the diet of reptiles. Proceedings of the Zoological Society. Bihang Till K. Svenska Vet.-Akad. Handlinger. Vol. 28, Part 4 (8):3-51. Lutcavage, M. E., P. G. Bushnell, and D. R. Jones. 1990. Oxygen transport in the leatherback sea turtle, Dermochelys coriacea Physiological Zoology. 63(5): 1012-1024. Lutcavage, M. E., P. G. Bushnell and D. R. Jones. 1992. Oxygen stores and aerobic metabolism in the leatherback sea turtle. Canadian Journal of Zoology. 70(2): 48-351. Lutcavage, M. E. and P. L. Lutz. Diving Physiology. Chap. 10. pp. 227-296. In: Biology of Sea Turtles P. L. Lutz and J. A. Musick, eds. CRC Press, Boca Raton. 432 pp. Lutz, P. L., A. Bergy and M. Bergy. 1989. Effects of temperature on gas exchange and acid-base balance in the sea turtle Caretta caretta at rest and during routine activity. Journal of Experimental Biology. 144: 155-169. Maloney, J. E., C. Darian-Smith, B. Russell, M. Varghese, J. Cooper, and C. J. Limpus. 1989. An evolutionary link for developing mammalian lungs. Journal of Developmental Physiology. 12: 153-155. Marshall, A. T. 1989. The duct system of the lacrimal salt gland of the green sea turtle, Chelonia mydas Cell and Tissue Research (1989) 257: 399-404. Miller, Jeffrey. D. 1985. Embryology of Marine Turtles. pp. 269328. In: Biology of the Reptilia Vol. 14 (Development A), C.Gans, F. Billett, and P.F. A. Maderson, eds. Academic Press. New York. 763 pp. Nilsson, S. 1983. Autonomic Nerve Function in the Vertebrates Springer-Verlag. New York. 253 pp. Noble, G. A. and E. R. Noble. 1940. A Brief Anatomy of the Turtle Stanford University Press, Stanford. 48 pp. Ottaviani, G. and A. Tazzi. 1977. The lymphatic system. Chap.4. pp: 315-462. In: Biology of the Reptilia Vol. 6. (Morphology E), C. Gans and T. Parsons, eds. Academic Press. New York. 505 pp. Owens, D. W. Hormones in the life history of sea turtles. Chap. 12. p. 315-341. In: Biology of Sea Turtles P. L. Lutz and J. A Musick, eds. CRC Press. Boca Raton. 432 pp. Owens, D. W. and G. J. Ruiz. 1980. New methods of obtaining blood and cerebrospinal fluid from marine turtles. Herpetologica. 36(1): 17-20. Parsons, T. S. 1958. The Jacobsen's organ of turtles. The Anatomical Record 132(3 November): 486. Parsons, T. S. 1970. The nose and Jacobsen's organ. In: Biology of the Reptilia Vol. 2 (Morphology B). C. Gans and T. Parsons, eds. Academic Press, New York. pp. 99-191. Parsons, T. S. and J. E. Cameron. 1977. Internal relief of the digestive tract. Chap. 2. pp. 159-179. In: Biology of the Reptilia Vol. 6. (Morphology E). C. Gans and T. Parsons, eds. Academic Press. New York. 505 pp. Perry, S. F. 1998. Lungs: comparative anatomy, functional morphology, and evolution. pp. 1-97. In: Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt, eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca, NY, USA, 660 pp. Perry, S. F., C. Darian-Smith, J, Alston, C. J. Limpus and J. E. Maloney. 1989. Histological structure of the lungs of the loggerhead turtle, Caretta caretta before and after hatching. Copeia. 1989 (4): 1000-1010. The Anatomy of Sea Turtles 167

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Pritchard, P. C. H. 1979. Encyclopedia of Turtles T.F.H. Publications, Inc. Ltd. Neptune, NJ. 895 pp. Pritchard, P. C. H. 1988. A survey of neural bone variation among recent chelonian species, with functional interpretations. Acta Zoologica Cracoviensia. 31(26), 625-686. Rabl, C. 1910. Bausteine zu einer Theorie der Extremitten der Wirbeltiere. I. Teil. II. Bau Entwicklung des Carpus und Tarsus der Schildkrten. Leipzig. Verlag Von Wilhelm Englelmann. 76-289. Rainey, W. E. 1981. Guide to Sea Turtle Visceral Anatomy NOAA Technical Memorandum NMFS-SEFC-82. Panama City. 85 pp. Raynaud, A. 1983. Animal morphogenesis. A scanning electron microscopic study of the epithelial structures appended to the visceral arches of the embryo of the leathery turtle ( Dermochelys coriacea V.). Compt Rendu Acadamie des Sciences Paris (Series III). 296(6): 297-302. Romer, A. S. and T. Parsons. 1986. The Vertebrate Body 6th edition. University of Chicago Press. Chicago. 679 pp. Rowe, T. 1986. Homology and Evolution of the deep dorsal thigh musculature in birds and other reptilia. Journal of Morphology. 189:327-346. Ryke, W. de. 1926. The vascular structure of the kidney in Chrysemys marginata belli (Gray) and Chelydra serptentina (L.). The Anatomical Record. 33 (3): 163-177. Saito, K., T. Shoji, I. Uchida, and H. Ueda. 2000. Structure of the olfactory and vomeronasal epithelia in the loggerhead turtle Caretta caretta Fisheries Science. 66(2): 409-411. Sapsford, C. W. 1978. Anatomical evidence for intracardiac blood shunting in marine turtles. Zoologica Africana. 13(1):57-62. Schaffner, F. 1998. The liver. pp. 485-532. In: Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt, eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca. 660 pp. Schumacher, G. H. 1973. The head muscles and hyolaryngeal skeleton of turtles and crocodilians. pp. 101-199. In: Biology of the Reptilia 4 Vol. (Morphology D). C. Gans and T. Parsons, eds. Academic Press. New York. Schumacher, G.-H. 1985. Comparative functional anatomy of jaw muscles in reptiles and mammals. Fortschritte der Zoologie, Band 30. pp 203-212. In: Vertebrate Morphology H. R. Duncker and Fleischer, eds. Gustav Fischer Verlag. New York. Shelton, G. and W. Burggren. 1976. Cardiovascular dynamics of Chelonia during apnoea and lung ventilation. Journal of Experimental Biology. 64:323-343. Solomon, S. E. 1985. The morphology of the kidney of the green turtle ( Chelonia mydas L.). Journal of Anatomy. 140(3):355-369. Tanaka, Y. 1998. Structure of the reptilian spleen. pp. 533-586. In: Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca. 660 pp. Tanner, W. W. and D. F. Avery. 1982. Buccal floor of reptiles, a summary. The Great Basin Naturalist. 43(3): 273-349. Thompson, J. S. 1932. The anatomy of the tortoise. The Scientific Proceedings of the Royal Dublin Society. 20 (28):359-461. Thompson, S. M. 1980. A comparative study of the anatomy and histology of the oral cavity and alimentary canal of two sea turtles: the herbivorous green turtle Chelonia mydas and the carnivorous loggerhead turtle Caretta caretta M.S. Thesis. James Cook University. 313 pp. Underwood, G. 1970. The Eye. In: Biology of the Reptilia C. Gans and T. Parsons, eds. Vol. 2 (Morphology B), Academic Press, New York. Pp. 1-97. Walker, Jr., W. F. 1973. The locomotor apparatus of Testudines. Chap. 1. pp. 1-100. In: The Biology of the Reptilia Vol. 3. (Morphology). C. Gans and T. S. Parsons, eds. Academic Press. New York. Walls, G. L. The reptilian retina. I. A new concept in visual-cell evolution. In: The Vertebrate Eye pp. 892-915. Wang, T., A.W. Smits, and W. W. Burggren. 1998. Pulmonary function in reptiles. pp. 297-374. In: Biology of the Reptilia Vol. 19 (Morphology G). C. Gans and A. S. Gaunt, eds. SSAR Contributions to Herpetology, Vol. 14. Ithaca. 660 pp. Wibbels, T., D. W. Owens, and D. Rostal. 1991. Soft plastra of adult male sea turtles: an apparent secondary sexual characteristic. Herpetological Review. 22(2): 47-49. Winokur, R.M., 1982. Erectile tissue and smooth muscle in snouts of Carettochelys insculpta Trionchids and other Chelonia. Zoomorphology 101:83-93. White, F. N. 1978. Circulation, a comparison of reptiles, mammals, and birds. pp.51-59. In: Respiratory Function in Birds, Adult and Embryonic J. Piiper, ed. Springer-Verlag, New York. Wolke, R. E. and A. George. 1981. Sea Turtle Necropsy Manual NOAA Technical Memorandum NMFS-SEFC-24. Wright, A. H. and A. A. Wright. 1958. Herptelogical Terminology Tulane University. 34 pp. Wyneken, J. 1996. Sea turtle locomotion: mechanisms, behavior, and energetics. Chap. 7., pp. 165-198. In: Biology of Sea Turtles P. L. Lutz and J. A Musick, eds. CRC Press, Boca Raton. 432 pp. Zug, G. R. 1966. The penial morphology and the relationships of Cryptodiran turtles. Occasional Papers of the Museum of Zoology. University of Michigan. 647: 1-24. SELECTED BIBLIOGRAPHY The Anatomy of Sea Turtles 168

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INDEX Aabdominal scutes, 1-2, 4, 31 abdominal vein, 72, 7475, 79, 100, 101 abductors, 59-61 abducens nerve, 127-128, 150, see cranial nerves accessory urinary bladder, 153-156 acoustic nerve, 151, 152 acetabulum, 54-56, 152-155 acromion processes, 35-37, 51-52, 59, 61-63, 74-75, 111, 116 adductor femoris, 71, 73, 145 adductors, 56, 60, 65, 68, 70-73, 143 adenohypophysis, see pituitary adrenal arteries, 78, 83-84 adrenal gland, 42, 84, 106, 124 afferent renal vessels, 154 aglandular segment, 160, 162 airway, 105-107, 109 albumen, 162 albumin, 119 alveolar surface, 26-27 ampulla of Vater, 111, 113 anal scutes 1-2, 4, 31 anatomical position, 1 anatomical terminology, 1 angular, 9, 11 anterior pancreatic veins, 103 anterior pancreaticoduodenal artery, 78, 80 anterior subscapular arteries, 77, 141 aortas, 37-38, 74, 76, 83, 117, 124, 156, arteries, 37-38, 41-42, 59, 62-63, 74, 76-86, 95, 101, 103, 105, 116 118, 124, 154, 156 astragalus, 56-58 atlas, 9, 44-45, 136, 139 atria, see atrium atrium, 38, 74, 121 auditory canal, 9, 11, 151 auditory nerve, 152 axial muscles, 68 axial skeleton, 43 axillary artery, 38, 77 axillary nerve, 145 axillary scale, 122 axillary vein, 79, 85 axis, 9, 45, 139 azygos artery, 86 azygos vein, 79, 85-86Bbasisphenoid, 9, 12, 125 BD, see body depth beak, see rhamphotheca biceps brachii, 59, 61-63, 65, 67, 86, 145 biventer cervical, 68, 87, 89-93 bladder, 40-41, 153-155 body depth, 31 brachial artery, 77, 99 brachial plexus, 59, 64, 141-143, 145 brachial vein, 79, 85 brachiocephalic artery, see brachiocephalic trunk brachiocephalic trunk, 38, 74, 76-78, 116, brain, 8, 42, 105, 115-116, 125-141, 146, 152 braincase, 8-9, 12, 41, 115-116, 125, 130, 139-140 bronchi, see bronchus bronchus, 40-41, 85, 105-107Ccalcaneum, 56-58 carapace scutes, 1-2, 4-8, 26-27, 102 carapace length, 28-29 carapace width, 28, 30 carapace, 1-2, 4-7, 26-30 Caretta caretta 4, 6-7, 16-17, 25, 27, 4146, 50-51, 55, 71, 80, 86, 92, 94, 97, 101, 106, 108, 112, 120, 125, 129-132, 147, 150-151, 155 carotid artery, 69, 70, 76-78, 80, 117-118, 136 caudal artery, 83-86, see vertebral artery caudal veins, 79, 102 caudal vertebrae, 45-46, 155 cavernous bodies, 161 cavum arteriosum, 74, 104 cavum pulmonae, 74, 104 cavum venosum, 74, 104 CCL, see carpace length CCLmax, see curved carapace length CCLmin, see curved carapace length CCW, see curved carapace width central nervous system, 125-141 centrale, 52-54 cerebellum, 42, 126-129, 131-141 cerebral aqueduct, 126-128, 132, 134 cerebral hemispheres, see cerebrum cerebrum, 42, 127, 129, 131-141 cervical vertebrae, 9, 44-45, 66, 80, 94, 141-142 Chelonia mydas 4-5, 13-15, 25-26, 46, 94, 98, 104, 110, 112, 119-121, 122-123, 126, 130, 133-134, 146, 156-157 Cheloniidae, 2 Cheloniids, 2-5, 11, 26-27, 35, 42, 46, 49, 51-53, 55, 62, 64, 71, 88, 104, 106, 110, 116, 129, 136-137, 141, 143-144, 147 choroid, 151 ciliary body, 151 circulation, 41, 74-104 circulatory system, 41, 74-104 CIRCUM, see circumference circumference, 32 claws, 1-2, 5-7, 52, 165 clitoris, 154, 164-165 cloaca, 32, 39-42, 75, 83, 102, 108, 114, 153-154, 157, 160, 162-165 cloacal veins, 79, 102 CNS, see central nervous system cochlea, 146, 152 coeliac artery, 78, 80, 82 collecting tubules, 154 colon, 39-41, 108, 111-112, 114, 121, 158 columella, see stapes common bile duct, 39, 108, 111-113, 119-121 common cardinal vein, see precava common carotids, 77-78 common iliac arteries, see iliac arteries common mesenteric vein, 79, 100, 103 cones, 151 conjunctiva, 147, 149 coracoid processes, 35-37, 51-52, 59, 6164, 66-68, 74-75, 100, 111, 114 cornea, 147, 151 corporus albicans, see corpora albicans corporus luteum, see corpora luteum corpora albicans, 159 corpora luteum, 159 corpus albicans, see corpora albicans corpus luteum, see corpora luteum corpus cavernosum, 162-163 cortex, 154 costal arteries, 78-79, 83, 124 costal scutes, see lateral scutes costal veins, 78-79, 83, 10, 102 cranial nerves, 42, 68, 98, 127-129, 131140, 150-151 crural nerve, 143-145 crural veins, 79, 100-101 CT images, 43, 50 curved carapace length, 28-29 curved carapace width, 30 curved plastron length, 31Ddeferent ducts, see vas deferens dentary, 9, 11, 23, 44, 68, 131-132, 135 dermal ossicles, 49 dermochelyid, 4-5 Dermochelyidae 4-5 Dermochelys coriacea 4-5, 23-25, 42, 107-108, 111-112, 115, 127, 129-130, 139-141, 148-149, 160, 162, 165 descending vena cava, see precava diencephalon, 126-127 digital arteries, 77-78 digital veins, 85 distal convoluted tubule, 154 dorsal aorta, 41, 78, 80, 83-86, 124, 156 dorsal brachial vein, 78 dorsal muscles, 65-67, 87-93, 102 duodenal veins, 79, 100, 103 duodenum, 39, 80, 82, 108, 111-113, 119-121 dura mater, 42, 125, see meningesEear, 109, 126, 129-130, 146, 151-152 efferent ductules, 162 efferent renal vessels, 79, 154 entoplastron, 50-52 epididymi, see epididymis The Anatomy of Sea Turtles 169

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epididymis, 156, 162-163 epigastric arteries, 78, 83-85, 102 epigastric vein, 79, 102 epimeningeal veins, 125 epiphysis, see pineal epiplastron, 50 Eretmochelys imbricata 4, 6-7, 21-22, 2526, 46, 94, 105, 108, 112, 120, 122, 129130, 137-138, 142, 144, 154 epiphysis, see pineal esophageal arteries, 77-78 esophageal veins, 98 esophagus, 38-39, 69-70, 77, 83, 98, 108111, 117, 131, 135, 137-140 ethmoid, 125 Eustachian tube, 109, 152 excretory system, 153-155 external iliac arteries, 78, 84 external iliac vein, 100, 102 external jugular vein, 83, 85-98 external nares, 146, 148 external rectus muscle, 150 extrastapedial process, 152 eye muscles, 150-151 eyelids, 147-149 see lids eyes, 42-43, 59, 115, 125-126, 130, 133, 146-151Ffacial nerve, 68-69, see cranial nerve femoral scutes, 1-2, 4, 30 femoral artery, 78, 84, 101 femoral nerve, 142-145 femoral vein, 79, 100 femur, 55-58, 70 fibula, 55-58, 70 flexor tibialis, 71-73, 101-102, 144-145 flippers, 2, 5-7, 31-32, 35, 37-38, 43, 51-54, 59, 61-62, 65-67, 77, 99, 141-143, 145 follicles, 41, 157, 159-160, 162 fontanelles, 46, 48, 50 foot extensors, 71, 145 forebrain, 126-127, 139 forelimb muscles, 62, 65 fourth ventricle, 127, 132, 134, 138 frontal bone, 9, 125, 131, 139 frontal scale, 3 frontoparietal scale, 3, 116Ggallbladder, 39-40, 80, 113, 119 gastric artery, 78, 80-82 gastric vein, 79, 82 gastropulmonary ligament, 106, 111 genital papilla, 153-154, 163 genital papillae, see genital papilla glandular segment, 160-162, see oviduct glenoid fossa, 51-52 glomerulus, 154 glossopharyngeal, 68, see cranial nerves glottis, 38, 44, 105, 108, 134-140 gonadal arteries, 78, 83-84 gonadal ducts, 85, 153, see vas deferens, oviducts,41, 156-163 gonadal veins, 79, 100 gonads, 40-42, 83, 85, 100, 153, 155, 159 great vessels, 35, 37-38, 76-77, 80, see aortas, pulmonary trunk greatest length, 29, see carapace length green turtle, see Chelonia mydas gubernaculum cordis, 37, 38, 74, 76 gular, 4Hhaemorrhoidal artery, 78, 85 Harderian gland, 114, 150-151 hawksbill, see Eretmochelys imbricata head length, 30 head scales, 3, 130 head width, 30 heart, 35, 37, 38, 72-80, 85, 104, 111, 116117, 119 hepatic portal system, 100, 102-103, 119 hepatic portal vein, 85, 100, 102-103, 119 hepatic vein, 79, 100, 119 hepatopulmonary ligament, 106 hind limbs, 2, 43, 102, 145 hindbrain, 126-127 hip muscles, 71-73, 102, 145 HL, see head length humeral, 1-2, 4, 31 humerus, 52-55, 59-60, 64, 67, 77, 141, 143 HW, see head width hyoid, 9, 38, 43-44, 68-70, 95, 105, 109, 131, 138-141 hyoplastron, 50, 121 hypogastric vein, 79, 102 hypoglossal, 68, 127-128, see cranial nerves hypoplastron, 50, 121 hypothalamus, 127Iidentification, 4-8, 13-27, 50-51 ileum, 39, 103, 108, 112 iliac arteries, 78, 84-86 iliac veins, 79, 100, 102, 154, 163 ilium, 46, 54-56, 71, 143-144 imbricate, 7 inferior mesenteric vein, 103 inferior oblique muscle, 150-151 inferior rectus muscle, 150-151 inframarginal, 4-5, 7-8, 34, 64, 120-122 infundibulum (brain), see pituitary infundibulum (oviduct), see ostium inner ear, 146, 151-152 interanal, see anal scutes intergular scute, 1-2, 31 intermediate segment, 154 intermedium, 52-54 internal brachial vein, 79, 85 internal choanae, see internal nares internal iliac arteries, 78, 84-85 internal iliac veins, 163 internal nares, 10, 13, 21, 22, 109, 146 internal rectus muscle, 150 interparietal scutes, 3 iris, 147-150 ischiadic veins, 102 ischiadicus nerve, 145 ischial tuberosity, 72 ischium, 54-56, 71JJacobsen's organ, see vomeronasal organ jaws, 3, 6, 8, 9, 13, 16, 18-19, 21, 23, 2627, 44-46, 61, 71 jejunum, 41, 110, 114 jugal, 9, 11-12 jugular vein, 72, 81, 84, 87-100, 120KKemp's ridley, see Lepidochelys kempii kidney, 40-42, 83-84, 86, 100, 102, 104, 106, 114, 124, 153-155, 157, 162Llamellar bone, 52, 55 large intestine, 38-39, 41, 84, 108 lateral scutes, 1-2, 4-9, 49 lateral ventricles, 132, 134 leatherback, see Dermochelys coriacea left aorta, 38, 40, 74, 76, 78, 80, 82-83, 118 lens, 150-151 Lepidochelys kempii 4, 7-8, 18, 20, 25, 27, 41, 46, 51, 67, 94, 106-107, 129, 135136, 146, 164-165 Lepidochelys olivacea 4, 7-8, 19-20, 25, 27, 67 leptomenix, 125 lids, 147-149 limbus (= limbas), 151 lipoidal veins, 79, 100 liver, 37-40, 74-75, 80-81, 102, 106, 108, 111, 113-114, 119, 121, 157 loggerhead, see Caretta caretta longus colli muscles, 68, 70, 80, 98 loop of Henle, 154 lumbosacral plexus, see sacral plexus lung, 38-42, 74, 76, 83-85, 104-107, 156158, 162 lymphatic vessels, 74Mmagnum, 160, 162 marginal scutes, 1, 6-7, 28-29, 34, 46, 49, 89-90, 92, 95, 97, 102, 121 marginocostal artery, 77-78, 83 marginocostal vein, 79, 100, 102 maxilla, 9-11, 16-19, 21, 23, 135-136 maxillary, see maxilla The Anatomy of Sea Turtles 170 INDEX

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maximum head length, 30 maximum head width, 30 maximum length, 29 Meckel's cartilage, 11 medulla, see brain or kidney meninges, 94, 125, 134, 137, 139-140 menix, see meninges mesencephalon, 127 mesenteric arteries, 103 mesenteric vein, 79, 100, 103 mesentery, 39, 103, 120, 157 mesorchium, 156, 162 mesosalpinx, 157-158, 161 mesotubarium, 156-158, 160, 162 mesovarium, 156-157, 158 metacarpal, 52-54 metanephric duct, 152 metatarsal, 56-58 metencephalon, 126-127 methods for dissection, 32-42 midbrain, 126-127, 139 middle ear, 109, 152 minimum length, 29 Mllerian ducts, see oviducts muscle function, 59, 145 muscles, 35-37, 43, 52-53, 59-72, 85-87, 90, 92-94, 96-99, 101-102, 107, 132, 141-145, 150-151 myelencephalon, 126-127Nnares, 9, 10, 13, 21-22, 111, 116, 134, 148-151 nasal sac, see olfactory sac nasopharyngeal duct, 126, 133, 146 neck flexors, 68 nephrons, 154 nerves, 42, 59, 64, 68-69, 71, 73, 127-129, 141-145 nervous system, 59, 71, 125-145 neural bones, 45, 47-48 neurocranium, 8-9, 12, 115 neurohypophysis, see pituitary nictitating membrane, 147-150 nostrils, see external nares notch-to-notch length, see minimum length over-the-curve length, see carapace length nuchal bone, 45, 48, 51 nuchal scute, 2, 6-7, 28-29, 49, 89-95, 97Ooculomotor nerve, see cranial nerves olfactory bulb, 42, 127, 129, 131-140, 146 olfactory nerve, 127-128, 131-132, 134141, 146 olfactory sac, 105, 125-126, 131-140, 146 olfactory tracts, 42, see olfactory nerve olive ridley, see Lepidochelys olivacea opisthotic, 12, 68, 125 optic chiasma, 127, 132 optic lobes, 42, 126-127, 129, 131-137, 141 optic nerve, 127-129, 131-138, 140, 151, see cranial nerves orbits, 16, 18-20, 23, 42-43, 147 ostium, 157-158, 160-162 otic notch, 9, 11, 151 ovaries, 41, 83, 153, 156-160, see gonads over-the-curve measurements, 28-30 over-the-curve length, 28 oviducts, 41, 154, 156-162Ppalate, 8, 10, 13-19, 21-27, 109, 132-134, 139 palatine, 10, 131 palpebral scales, 147 pancreas, 38-39, 80, 82, 103, 109, 111, 119-120 papilla (esophageal), 110-111, 139-141, 146 papilla (urogential), 114, 163, 153-154, 165 parathyroid, 116-118 parietal bone, 9, 11-12, 16, 68, 125, 131, 139 parietal notch, 16, 19, 21, 23 parietal scale, 3, 11-12, 16 pectoral apparatus, see pectoral girdle pectoral artery, 63-64, 77-78 pectoral girdle, 35, 37, 43, 51, 59-60, 64, 107, 111 pectoral muscles, 36, 59-62, 66, 76-77, 82, 85-86, 100, 111, 121, 141-143, 145 pectoral scute, 1-2 pectoral vein, 63, 79, 86, 100 pelvic girdle, 43, 54-55, 59-60, 107, 114 pelvic muscles, 100, 102, 143-145 pelvic vein, 61, 100 pelvis, see pelvic girdle penis, 102, 153, 162-164 pericardial sac, 74, pericardial veins, 79, 100 pericardium, 37-38, 63, 74-76, 111 peripheral bones, 42, 45-46, 48, 50, 64 peripheral nerves, 141-145 peritoneum, 35-37, 40, 74, 76, 100, 106, 114, 119, 121, 153, 157, 162 peroneal nerve, 71, 73, 143-145 phalanges, 43, 52-54, 55-58 pia mater, see leptomenix pineal, 116, 127, 129, 131-132, 134-140 pisiform, 52-54, 67 pituitary, 42, 115-116, 127-128, 131-132, 134, 136, 140 PL, see plastron length plastron length, 31 plastron,1-2, 4-6, 31-32, 34-35, 42-43, 46, 50-51, 59, 110, 121-123, 165 pleural bones 2, 45, 48, 64 popletial veins, 100-101 pores, 4, 7-8, 35, 121-123 portal systems, 79, 100, 119 postcava, 79, 84, 100 postcentral scutes, 2, 28, see suprapygal scute posterior muscles, 58-60, 71-74, 102 posterior pancreatic veins, 79, 103 posterior pancreaticoduodenal artery, 80 postorbital bone, 9, 11-12, 18 precava, 76, 79, 85, 88, 98-99 prefrontal bone, 9 prefrontal scale, 2, 4-6 premaxilla, 9-11, 16, 18-19, 21, 131, 134, 139 prootic, 12, 68, 125 proximal tubule, 154 pterygoid, 9-10, 12, 19, 131, 136 pterygoideus muscle, 70 PVTL, see tail length pubis, 41, 54-56, 59, 61, 111, 154-155 puboischiofemoralis, 71-73, 145 pubotibialis, 71-73, 101, 145 pulmonary artery, 37-38, 74-78, 104-105 pulmonary system, 105-107 pulmonary trunk, 38, 76-78, 84, 104 pulmonary veins, 79, 85, 104 pupil, 147-151 pygal, 45, 48 pyloric sphincter, 39, 81, 108, 111-113 pyramidalis muscle, 150-151Qquadrate, 11 quadratojugal, 11-12, 69, 151Rradial artery, 77-78 radial nerve, 64, 141-143, 145 radiale, 52 radius, 52-54, 59, 67 Rathke's glands, 120-123 Rathke's pores, 8, 35, 121-123 recessus cavi tympani, 152 rectum, 38-41, 102, 108, 112, 114, 153154, 163 renal arteries, 78, 83-84, 86, 154, 156 renal capsule, 154 renal corpuscles, 154 renal portal vein, 79, 100, 102, 154 renal veins, 114, 154, 157 respiratory muscles, 59, 62, 64, 141, 142-145 rete system, 85 retina, 150-151 rhamphotheca, 6, 26-27, 30, 131, 132 ribs, 43, 45-51 right aorta, 38, 40, 75-78, 83, 118 rods, 151Ssacral plexus, 71, 141, 143-145, 155 sacral vertebrae, 45-46, 54-55, 143, 155 salt gland, 42, 115, 125, 139-140, 146, 150-151 scales, 1-8, 13, 116, 122-123, 151-152 scapula, 37, 51, 52, 59, 64-67, 77, 83, 85, 88, 99 scapular vein, 79, 85, 99 sciatic artery, 78, 84-85, 101 The Anatomy of Sea Turtles 171 INDEX

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sciatic nerve, 73, 101, 143-145 scleral ossicles, 43, 150 SCLmax, see carapace length SCLmin, see carapace length scutes, 1-2, 4-7, 29, 31, 34, 46, 49, 102, 120-122, 165 SCW, see carapace width secondary palate, 16-18, 21-23 sella tursica, 115-116, 128, 132 semicircular canals, 152 sense organs, 8, 146-152 sexual dimorphism, 164-165 shell gland, see glandular segment shell membrane, 162 shoulder muscles, 62, 64, 66-67, 99, 107, 140, 143 sinus venosus, 38, 74, 76, 79, 85, 100, 111, 119 skull, 8-25, 42-44, 115, 128-129, 132140, 152 small intestine, 38-39, 103, 108, 111-112, 120-121 snout, 5, 8, 13, 16, 18, 20-21, 26-27, 42 species identification, 1-27, 50-51 spinal accessory nerves, 127-129, see cranial nerves spinal cord, 47, 127, 129, 138-139, 141 SPL, see plastron length splanchnocranium, 8-9 spleen, 39, 82, 103, 108, 119-120 splenial, 9, 11 splenic vein, 79, 103 squamosal, 9, 11-12, 17, 68-69, 151 standard carapace length, 28 standard measurements, 28-32 stapes, 12, 152 statoacoustic nerve, see cranial nerves, acoustic nerve stomach, 38-39, 80-82, 102-103, 106, 108112, 119-121 straightline carapace lengths 28-29 straightline measurements, 28-31 subclavian arteries, 38, 76-78, 99, 115-118 subclavian vein, 79, 84, 88 sulcus spermaticus, see urethral groove superficial limb retractors, 61, 72 superior mesenteric artery, 78, 80 superior oblique muscle, 150-151 superior rectus muscle, 150-151 superior vena cava, 85, 88, see precava supernumery scales, 3 supracaudal scute, 2, 28, 49 supraoccipital, 9, 16, 30, 68, 70, 125, 131, 134, 137, 139 supraocular scales, see scales suprapygal bone, 45, 48 suprapygal scutes, see supracaudalTtail length, 32, 164 tail, 46, 68, 72-73, 83, 85 tapetum lucidum, 151 tarsals, 56, 57 taste buds, 148 tela choroidea, 125-126, 131-132 telencephalon, 126-127 temporal bone, see squamosal temporal scale, 3 tendons, 59, 64-65, 67-68, 71, 101 terminology, 1, 85, 145 testes, see testis, gonads testis, 40-41, 82, 100, 114, 153, 156, 159, 162, 163, see gonads thalamus, 127 third ventricle, 127, 132, 134 thoracodorsal artery, 99 thymus, 35, 38, 76, 116-118 thyroid artery, 38, 76-78, 116 thyroid, 35, 37-38, 76-77, 85, 116-117 thyroscapular vein, 79, 85 tibia, 57-58 tibial nerve, 71, 143-145 tibial vein, 100 TTL, see tail length tongue, 38, 44, 68, 105, 108-109, 131, 133, 135-136, 138-140, 146 tools, 33 trachea, 37-41, 6970, 76, 95-96, 105-106, 109, 111, 117, 131, 133, 135, 137-139 transverse branch, see transverse cervical branch transverse cervical branch, 87, 94-95 transverse cervical muscles, 68, 86-97 trigeminal nerve, 68, 127-129, see cranial nerves trochlear nerve, 127, 150, see cranial nerves tympanic cavity, 152, see otic notch tympanic scale, 3, 151 tympanum, 151-153Uulna, 52-54 ulnar artery, 77-78 ulnar nerve, 141-143, 145 ulnare 52-54 ultimobranchial bodies, 116-118 ureters, 41-42, 114, 153-154 urethral groove, 163 urinary bladder, 40-41, 114, 153-155, 158 urinary papilla, 114, 153-154 urodeum, 114, 153, 157, 160 urogenital papilla, 153-154 urogenital system, 41, 153-165 uvea, 150-151Vvagina, 160, 162 vagus nerve, 98, 127-128, see cranial nerves vas deferens, 41, 156, 159, 162-163 vascular circumflex, 85 veins, 79, 82, 85-98, 100-104, 114, 119, 125, 153, 157, 161, 163 ventral cervical arteries, 77, 95, 117-118 ventral hip muscles, 71-73, 145 ventral muscles, 59-60, 62, 65, 107, 143 ventral neck muscles, 68-69 ventricle (of brain), 126-128, 132, 134, 136, 138 ventricle (of heart), 38, 74-77, 102-104, 111, 118, 121 vertebrae, 47-48, 141-143, 155 vertebral arch, 45, 47 vertebral artery, 78, 84-85, 95 vertebral body, 9, 45, 47 vertebral branches, 83, 88-96 vertebral column, 41-42, 45, 102, 106-107 vertebral scutes, 1-2, 4, 6, 8, 49 vertebral vein, 79, 88-89, 93, 102 vesicular veins, 78, 100 vestibular, 146, 152 vision, 147-151 vitreous body, 150 vomer, 10, 18-19, 21 vomeronasal organ, 146 VTTL, see tail lengthXxiphiplastron, 50 The Anatomy of Sea Turtles 172 INDEX