<%BANNER%>

Description, mechanism and associated behaviors of substrate and airborne vibrations produced by Jadera haematoloma (Hem...

Permanent Link: http://ufdc.ufl.edu/UFE0042334/00001

Material Information

Title: Description, mechanism and associated behaviors of substrate and airborne vibrations produced by Jadera haematoloma (Hemiptera Rhopalidae)
Physical Description: 1 online resource (39 p.)
Language: english
Creator: Zimmerman, Ariel
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: communication, courtship, hemiptera, insect, rhopalidae, stridulation
Biology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The soapberry bug, Jadera haematoloma is a common insect found all across the United States. In the state of Florida, it is most often spotted in large urban aggregations around its host tree, the goldenrain tree. Though these insects are well-known to the general public and to science, this is the first time it has been shown that they produce sounds which may be used for acoustic communication. This discovery is especially important because soapberry bugs are from a family of insect which until now has not been known to communicate using what scientists call stridulation; scraping a pick-like appendage along a comb underneath the wings. These sounds are quiet, but audible to the human ear, and only occur when two adults of the species encounter one another. These sounds may be important for furthering our understanding of mating and aggregation behavior in this and other insect species.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Ariel Zimmerman.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Gillooly, James.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042334:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042334/00001

Material Information

Title: Description, mechanism and associated behaviors of substrate and airborne vibrations produced by Jadera haematoloma (Hemiptera Rhopalidae)
Physical Description: 1 online resource (39 p.)
Language: english
Creator: Zimmerman, Ariel
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: communication, courtship, hemiptera, insect, rhopalidae, stridulation
Biology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The soapberry bug, Jadera haematoloma is a common insect found all across the United States. In the state of Florida, it is most often spotted in large urban aggregations around its host tree, the goldenrain tree. Though these insects are well-known to the general public and to science, this is the first time it has been shown that they produce sounds which may be used for acoustic communication. This discovery is especially important because soapberry bugs are from a family of insect which until now has not been known to communicate using what scientists call stridulation; scraping a pick-like appendage along a comb underneath the wings. These sounds are quiet, but audible to the human ear, and only occur when two adults of the species encounter one another. These sounds may be important for furthering our understanding of mating and aggregation behavior in this and other insect species.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Ariel Zimmerman.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Gillooly, James.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042334:00001


This item has the following downloads:


Full Text

PAGE 1

DES CRIPTION, MECHANISM AND ASSOCI ATED BEHAVIORS OF SUBSTRATE AND AIRBORNE VIBRATIONS PROD UCED BY JADERA HAEMATOLOMA (HEMIPTERA: RHOPALIDAE) By ARIEL F. ZIMMERMAN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010 1

PAGE 2

2010 Ariel F. Zimmerman 2

PAGE 3

To my pare nts 3

PAGE 4

ACK NOWLEDGMENTS I would like to thank Noah, my close friends at the University of Florida, as well my friends and family for their support while I wa s completing this research. I would also like to thank my committee and collaborator s, which include my advisor Dr. Jamie Gillooly, Dr. Richard Mankin, Dr. H.J. Brockmann, Dr. Ch ristine Miller, and Everett Foremann. Thanks are due also to Dr. S. Tonia Hsieh for the use and assistance with high-speed filming equipment, Dr. Susan Ha lpert at the Flori da State Arthropod Collections, and Ann Heatherington of the UF Department of Geology for assistance with SEM image collection. Funding for this research was provided by an NSF graduate research fellowship and University of Florida Alumni Fellowship. 4

PAGE 5

TABL E OF CONTENTS page ACKNOWLEDG MENTS..................................................................................................4LIST OF TABLES............................................................................................................6LIST OF FI GURES..........................................................................................................7ABSTRACT.....................................................................................................................81INTRODUC TION......................................................................................................92METHOD S..............................................................................................................12Jadera haematoloma Natural History and Collect ion..............................................12Description of Sounds Produced by J. haematoloma .............................................13Identification of the Mechanism of Sound Produc tion.............................................14Identification of Plectrum Us ing High-Speed Vide o Analyses...........................14Visualization of Stri dulitrum and Pl ectrum........................................................15Experimental Manipulation of The Stridulatory Apparat us................................16Behaviors Associated with Sound Pr oduction.........................................................17Statistical Analys is............................................................................................18Acoustic Response to Threat St imuli................................................................193RESULT S...............................................................................................................21Description of Sounds Produced by J. haematoloma .............................................21Identification of the Mechanism of Sound Produc tion.............................................22Behaviors Associated with Signal Pr oduction .........................................................234DISCUSSI ON.........................................................................................................26LIST OF RE FERENCES...............................................................................................35BIOGRAPHICAL SKETCH ............................................................................................39 5

PAGE 6

LIST OF TABLES Table page 3-1 Influence of participant sex and behav ior on whether or not sounds were produced during an encount er............................................................................29 6

PAGE 7

LIST OF FIGURES Figure page 3-1 Spectrogram comparison of airborne (a ) and substrate (b) vibrations of a male Jadera haem atoloma.................................................................................303-2 Oscillogram of a microphone recordi ng of a single burst showing impulse structur e.............................................................................................................313-3 Pulse interval, the time between the first and second pulse of a burst, is positively correlated with body length. (N = 19, R-sq = 0.5078, p=0.0006*). Triangles are females, circles are males............................................................323-4 SEM image of the stridulitrum loca ted on the ventral side of the left metathoracic wing of an adult male Jadera haem atoloma..................................323-5 SEM image of right abdominal tergites I and II with illustration of plectrum motion. ................................................................................................................333-6 Spectrograms of bursts from a male with wings (a b), and a male with wings removed (c, d). .................................................................................................34 7

PAGE 8

8 Abstract of Thesis Pres ented to the Graduate School of the University of Florida in Partial Fulf illment of the Requirements for t he Degree of Master of Science DESCRIPTION, MECHANISM AND ASSOCI ATED BEHAVIORS OF SUBSTRATE AND AIRBORNE VIBRATIONS PROD UCED BY JADERA HAEMATOLOMA (HEMIPTERA: RHOPALIDAE) By Ariel F. Zimmerman December 2010 Chair: James F. Gillooly Major: Zoology To understand patterns in the evolution of communication in a diverse group such as insects, a better understanding of t he diversity of communication systems is necessary. Using the abundant and well-studied soapberry bug, Jadera haematoloma Herrich-Schaeffer (Hemiptera: Rhopalidae) I describe for the first time the sounds made, the mechanism of sound production, and associated behavior in a member of the family Rhopalidae. Jadera haematoloma produced substrate and airborne vibrations simultaneously, which were short, and highl y stereotyped sounds produced at variable rates. Sounds were produced by anterior-poste rior movement of abdominal tergites I and II against a stridulitrum located on the vent ral surface of the metathoracic wing. Sounds were produced by a single adult male or female when physically touched by another adult, and were strongly associated with being crawled on by the approaching individual but were not produced in response to contact with other arthropods or when pinched with forceps. Vibrations by Jadera haematoloma are likely communication signals, which are produced using a mechani sm common to vibratory communication systems in closely related Heteropteran-Hemiptera.

PAGE 9

CHA PTER 1 INTRODUCTION Acoustic and vibratory communication is in credibly diverse and has arisen multiple times over evolutionary time in the Hemiptera. The evidenc e in support of multiple evolutionary origins of vibratory communication in this group is quite extensive due to the characteristic morphology of diverse vi bration-producing structures in multiple families (Tishechkin 2006, Ashlock and La ttin 1963, Polhemus 1994, Schaefer 1980, Schaefer and Pupedis 1981). Hemiptera o ccupy a wide array of niches and communicate in many different ecol ogical and behavioral arenas (Cocroft and Rodriguez 2005). By comparing the structur es used for vibratory communication among distantly-related taxa, we may be able to use Hemiptera to understand the behavioral and ecological pressures that drive acoustic conv ergence or diversification in this group. However, developing Hemiptera as a clade fo r studying acoustic evolution requires a good record of the diversity of signals and signal-producing structures with some taxonomic resolution, a record which is st ill incomplete. Here I present an in-depth investigation of the vibrations produced by a well-studied member of the family Rhopalidae (Hemipte ra:Heteroptera), Jadera haematoloma Herrich-Schaefer, and describe for the first time the mechanism an d behavior associated with vibrations in this family for the first time. The body parts used by other closely-re lated Hemiptera to produce vibrations provide clues to the mechanism that may be used by Jadera haematoloma Structures that are shared among closely related fam ilies through common decent may have been similarly recruited for vibr ation production in the Rhopali dae. Rhopalidae lies within the infraorder Pentatomomorpha, a diverse group that includes Lygaeidae, Pentatomidae, 9

PAGE 10

Coreidae and others (Henry 1997). In the P entatomomorpha, a tergal plate formed by the fusion of abdominal tergites I and II is commonly associated with vibratory communication and which may be used in Rh opalidae (reviewed by Vibrant-Doberlet and Cokl 2004, Gogala 2006). Two mechanis ms of the tergal plate have been proposed as the vibrational mechanism. The fi rst is as a plectrum used in conjunction with a wing stridulitrum (Leston et al. 1954, Ashlock and Lattin 1963, Schuh and Slater 1995). The second is as a tymbal; a bi-stable plate which pops in and out of two stable configurations, similar to that used by cicadas and planthoppers (Gogala et al.1974, Gogala 2006). The tymbal mechanism was first hypothesized in Cydnidae, where Gogala and colleagues (2006) showed that wax application between tergites I and II silenced low-frequency signals. S ubsequent replications of this technique have turned up conflicting results (Lawson and Chu 1971, Numata et al 1989). Other vibrations in Pentatomomorpha have been attributed to a tymbal mechanism without direct observation or manipulation of the tergum (Schaefer 1980, Vibrant-Doberlet and Cokl 2004). Using J. haematoloma it is possible to address not only the persistence of tergal plate involvement in sound pr oduction in Pentatomomorpha, but potentially also determine whether it functions as a tymbal or a plectrum. My goals were to: 1) describe the sounds produced by J. haematoloma using recording and sound analysis software, 2) de scribe the mechanism of sound production, using film and microscopy techniques, and 3) explore whether sounds produced may be used for communication among members of the same species or as aposematic threats to potential predators. To address these goals, I analyzed the sounds and substrateborne vibrations produced by J. haematoloma in detail. Using scanning electron 10

PAGE 11

microscopy and high-s peed video analysis, I i dentified the stridulitrum and plectrum used to generate sounds. I used experimental mani pulation of the plectrum to verify that the structures identified are essential for generating high and low-frequency acoustic components. I then compared J. haematoloma sounds to published examples of species that use a similar mechanism to produce vibrations. Before the sounds and sound-associ ated morphology presented here can be contributed to the body of liter ature on the diversity of insect signals, it is important to distinguish between ra ndom or incidental sounds and thos e that may serve a role in communication. To disprove that sounds are produced randomly, I filmed interactions and then asked whether sounds were a ssociated with specific behaviors and participants. I then identified intraand inter-s pecific interactions which were more likely to produce sounds such as a defensive response to predator threats (Masters 1979) or as an attractive signal to conspecifics (e.g Wenninger et al. 2009). This behavioral context will play an important role in our future understanding of how vibrations are used for communication in the Rhopalidae and other related families. 11

PAGE 12

CHA PTER 2 METHODS Jadera haematoloma Natural History and Collection. J. haematoloma is an abundant species of Rhopal id common throughout the continental US, which has been well-studied as an example of rapid evolution associated with plant host shift (Carroll and Boyd 1992). The Rhopalidae, also called the scentless plant bugs, are common throughout the world and include the well known boxelder bug ( Boisea trivittata Say). Jadera sp. play a role in reducing the seed productivity of a species of Sapindaceae ( Koelreuteria elegans Laxmann ) classified as a Class II Invasive by the Florida Exotic Pe st Plant Council (Carro ll et al. 2003, FLEPPC 2009). Rhopalids are pests in countries wh ere Sapindales such as Lychee and Longan are cultivated (Waite and Hwang 2002). In sp ite of their ecological and economic importance, a single recording of a male Arhyssus hyoscyami is the only documentation of vibratory signals in this group (formerly Corizus hyoscyami L. Gogala 1990). Adult and immature Jadera haematoloma were field collected in July and August 2009 beneath large (>6m crown height) specimens of the lo cal host, Golden Raintree, Koelreuteria paniculata v. bipinnata in Northwest Gainesville (Alachua County) and on the University of Florida campus. Adults we re captured from lar ge canopy aggregations using an 18 bag net beaten against branches containing aggregations. Identification was verified with the help of members of the Florida State Collection of Arthropods in Gainesville, FL (Slater and Baranowski 1978, Schuh and Slater 1995). Groups of up to 100 adults and nymphs were housed in two-liter plastic buckets with screen lids and given fresh host leaves and water from soak ed wicks. Host seeds were omitted from enclosures to accurately reflect seed availability in the field at the time of collection (no 12

PAGE 13

intact seeds were present at the collection site). The buckets were held in a growth chamber maintained at 260C with 14:10h L:D photoperiod to simulate summer temperature and photoperiod. Indi viduals were housed for up to two weeks before being returned to the field and replac ed by new field collections. Description of Sounds Produced by J. haematoloma To fully characterize the vibrations produced by J. haematoloma, it was important to record and describe both substrate and air borne (acoustic) vibrations, as well as identify variation among individuals. Acoustic and vibratory recordings of groups of individuals took place in a vibration-shie lded anechoic chamber (M ankin et al.1996) at the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL kept at 260C and 60% RH. To capture both acoustic and vibratory recordings, 10-12 individuals were placed in a cylindrical cage (6cm diameter x 10cm height ) made of 1mm metal screen mesh for 30 minutes. A Brel and Kjaer accelerometer for re cording substrateborne vibrations (Wenninger et al. 2009) was clipped to the top edge of the screen lid. These accelerometer recordings were coupl ed with acoustic recordings using a Brel and Kjaer microphone (Mankin et al. 2000) horiz ontally positioned atop a foam block 1 cm from the cage. Both acoustic and substr ate-borne vibrations were recorded at the same time to determine whether they were produced synchronously and to determine how each differed from the other. All recordin gs were digitized and saved on a computer using a commercially available speech ana lysis system (Wenninger et al. 2009). In order to determine whet her sex or body length influenced variation in the sounds produced, a separate set of recordin gs were made of adults of known sex and body length. Body length was measured as t he tip of the clypeus to the posterior edge of the last abdominal segment. 19 adults wh ose sex and body length were determined 13

PAGE 14

(Carroll et al. 1987) were individually placed in the anechoic chamber setup with an indiv idual who was silenced by waxing (see sil encing protocol below). I recorded three bouts of sound production for each individual to associate sound characteristics with body length measurements. I described sounds using the follo wing attributes: duration of continuous sound production, duration of isolated bursts, repetition rate, dominant frequency, maximum frequency range, impulse number, inter-pulse interval, and amplitude. Sound analyses and visualizations were conducted using Raven Pro v 1.3 (Cornell Lab of Ornithology 2008). Identification of the Mech anism of Sound Production. I used three approaches to identify the me chanism used to produce sounds by J. haematoloma I first used a series of high-speed vid eo recordings to identify structures which move specifically in association with sound production and wh ich could function as a plectrum, the basic mechanism most co mmon in terrestrial Heteroptera. After identifying a putative plectr um, I then captured high-resolu tion surface images of the articulating side of the hind wi ngs to determine whether t here was a stridulitrum which articulated with the putative pl ectrum. Lastly, I performed a series of loss-of-function manipulations to verify that I had correctly identified the structures involved in sound production. These consisted of removing su spected structures, or preventing their movement, and then recording any sounds produced by those individuals in conspecific interactions. Identification of Plectrum Us ing High-Speed Video Analyses To identify a putative plectrum, I searched for body part movements that corresponded to the rate and behaviors during brief periods of sound production. Individuals with wings removed were f ilmed using a high-speed video camera (250 14

PAGE 15

frames/s) fitted with a macro lens under infra-red illumin ation (Autumn et al. 2006). Individuals were placed in five groups of four into small (10x 8x4cm) clear plastic enclosures, and recorded for 15-second intervals encompassing acoustic activity. The specific behavioral context in which sounds were observed from behavioral trials made it simple to attribute sound re cordings to specific individuals being filmed. Because a single individual per interaction produces signals, film analysis was restricted to encounters in which the individual producing sounds was isolated within a frame to ensure that body part movements were correctl y attributed to the st ridulating individual. Synchronous high speed video and sound recordi ng was not available for this analysis, but video analysis was restricted to those 15-se cond periods of video in which sounds were being continuously produced. When repetitive movements were discovered, the cycle-rates were calculated by counting the number of cycles per second using Photron Fastcam Viewer (Photron Limited 2006). This calculation was used in place of synchronous high-speed sound and video recordi ng in order to determine whether the putative plectrum moved at a rate sufficient to generate the repetition rates observed during recording sessions. Visualization of Stridulitrum and Plectrum The results of the high-s peed video analysis strongly s uggested that the moving part, or plectrum, associated with sound produc tion was the plate formed by the fusion of abdominal tergites I and II. I cons idered whether the undersurface of the metathoracic wing possessed a stridulitrum that could be used in conjunction with the moving plectrum to produce sound. I us ed Scanning Electron Microscopy (SEM) to capture a surface image of t he underside of the metathor acic wing. Images were obtained using a variable-pressure scanni ng electron microscope (Zeiss Evo MA10, 15

PAGE 16

www.ze iss.com) run at 70Pa. The left metath oracic wing was removed from freezekilled specimens using forceps and then m ounted on carbon tape dorsal side down. The remaining wings were removed using forc eps, and the whole body placed venter-side down for images of the thorax and abdominal tergites I and II. One male and one female was included in the SEM image set that were typical of the distribution of body lengths observed in the population. Only images of males are presented for brevity. SEM images of the underside of t he metathoracic wing and abdominal tergites were completed at the Thermal Ionization Ma ss Spectrometry and Scanning Electron Microscope Laboratory in the University of Fl orida Department of Geological Sciences in February 2010. Experimental Manipulation of The Stridulatory Apparatus In an effort to verify t hat the structures identifi ed using high-speed video analysis and SEM imaging are essential for sound producti on, I silenced individuals by removing independently the stridulitrum and preventing movement of the plectrum. Twenty male individuals were collected that had previously been observed producing signals. I chilled 10 males for 10 minutes in an airtight container at -10 C, and removed fore and metathoracic wings by pulling at the wi ng base slowly. Following wing removal, individuals were allowed to rest and come to room temperat ure for one hour before being placed together in the interaction containers and recorded. When it was found that wing removal did not result in complete silencing, melted paraffin wax was applied beneath the wings of the remaining 10 males between abdominal tergites I and II after Gogala (1990). This prevented anterior-poste rior movement of the abdominal tergites. Care was taken not to wax the wings to the t horax so that any role of wing movement in 16

PAGE 17

sound production independent of plectrum movement could still be observed. Individu als were checked after waxing to ens ure that they still had complete use of all their legs, wings, and antennae and did not show any noticeable alterations of their behavior. Following wax applicat ion, the 10 males were pl aced in the interaction container together and recorded to det ermine if muting was complete. Behaviors Associated with Sound Production In order to identify behaviors that may be associated with sound production, I filmed field-caught individuals while recording sounds, and asked whether or not sounds occurred more frequently when certain behaviors occurred. Preliminary observations showed that sounds were not produced outside of encounter s between adults. Behavioral analysis was therefore restrict ed to encounters between individuals. Ten groups of four to ten adults were placed in flat rectangular plastic interaction containers (5cm x 8cm x 2cm) with one of t he two widest surfaces of the container replaced with a fine mesh screen. Interaction containers were held vertically with one clear surface facing a SONY HD Handycam video camera, illuminated from 0.5m above using a 120W incandescent light bulb, with the screened side facing the microphone. Filming took place through the non-mesh face of the container at normal speed using the HD macro setting. Fresh field-collected adult individuals were used for each recording session, and were allowed to acc limate for 30 minutes prior to the start of recording. Sound and video reco rding continued for 60 minutes. To standardize among group interaction trials I restricted this analysis to the first ten encounters following the 30-minute a cclimation period. Encounters were characterized as the period starting when two individuals at least one body-length apart initiate physical contact with any appendage and ending the moment they move to 17

PAGE 18

greater than one body length apa rt. Encounters were then characterized according to the relative speed of individuals entering into the encounter, the sex of participants, the presence or absence of specific behaviors, and whether or not sounds were produced. The relative speed of each individual moving into and away from a physical contact was measured in terms of body lengths/second, and assigned to each participant according to approaching and approached as the individual moving with the greatest or least velocity at the start of an encounter (re spectively). I categorized three encounterspecific behaviors in addition to recordi ng the sex and speed of encounter participants. I defined leg grappling as repeated leg to leg contacts made between two individuals, either facing one another or next to one anot her without thorax or abdomen contact. I designated body rocking as taking place w hen an individual rolled or rocked its entire body from side to side around the anterior-posterior axis. Lastly, when the approaching individual crawled completely on top of the approached individual, I referred to this as crawling onto which was chosen over mounting to emphasize that no effort was made to associate this behavior with copulation. The relative speed of each individual moving into and away from a physical c ontact was measured in terms of body lengths/second, and assigned to each partici pant according to approaching and approached as the individual moving with the greatest or leas t velocity at the start of an encounter. The first ten encounters fo r each group were then pooled together totaling 100 scored encounters. Statistical Analysis For the series of behavioral trials, I pooled the encounters across interaction trials to total 100 encounters. This pooling was ne cessary to achieve adequate numbers of suspected behaviors to associate with sound production. Encounters were categorized 18

PAGE 19

by target behavior, signaler sex, and approaching individual sex category. A two-way contingency table with sound/no sound as the response variable was created for each encounter type. A Fishers chi-squared test was then used to determine if there was a significant difference in the number of encounters featuring a specific behavior or participant sex that resulted in signaling. Two-tailed chi-squared values are reported because they are a more conservative representation of the difference between two groups than a one-tailed test (Fisher 1922). Data analysis was completed using JMP statistical software (SAS Institute 2008). Acoustic Response to Threat Stimuli To determine whether sounds may be used as defensive signals in response to threat, I recorded sounds produced during filmed interactions with ants, cockroaches, and simulated predation events. I used two types of threat st imuli: arthropod threats, and simulated vertebrate predator threats. Two adult individua ls were placed in a large petri-dish fitted with a screen lid and sus pended in the same manner as the normal interaction trials and were allowed to acc limate for 10 minutes while being filmed and recorded. Threat stimuli consisted of either four large (>5mm in length) carpenter ants (Pogonomyrmex sp) or two American cockroaches ( Periplaneta americana L.) of approximately 10mm body length. Following the acclimation period, the threat stimuli were introduced to the container, and interactions and sounds were recorded for 30 minutes. This procedure was repeated two times with new adult individuals for each arthropod threat. Because these insects are highly chemically protected (Aldrich et al. 1990a), it is possible that other invertebr ates do not pose a serious th reat. Therefore, simulated vertebrate predator threats were conducted using isolated adult males in the sound 19

PAGE 20

chamber while recording with a microphone. Adult males were used because the interaction trials suggested they were the mo st likely to produce sounds in conspecific encounters Six males were individually attacked by tugging on the legs and antennae with forceps on a stage in front of a reco rding microphone. A separate set of six adult males were individually picked up betw een the thumb and index finger and rolled between the fingers in front of the microphone four times fo r approximately 30 seconds each. 20

PAGE 21

CHA PTER 3 RESULTS Description of Sounds Produced by J. haematoloma Vibrations were detectable both in t he substrate and as audible sound; each type of vibration was produced synchronously. These vi brations consisted of repetitions of a single short (~25ms) stereotyped burst without any frequency modulation (N=10). Burst rate was highly variable among bouts (up to 40 signals/second), how ever the structure of each individual burst remained fixed fo r an individual. The frequency range of each acoustic burst was contained within 0.5 and 12 kHz. The first dominant frequency band spanned 1-5.5 kHz, the second higher frequency band spanned 7.5-10kHz. The frequency ranges of sounds and associated substr ate-borne vibrations were within the detection range of insect vibration sensi ng organs found in other species of plantdwelling Hemiptera (Cokl 1983, Shaw 1994). Within a burst, there was a clear paired couplet structure in the airborne component of the signal, which consisted of two short, distinct pulses. The following results were typical of all signals recor ded for the 19 individuals measured and sexed for body-size variation. The first pulse c onsistently showed a higher amplitude (power) than the second (Figure 3-1a). This twopulse couplet was less apparent in the substrate-borne signal than in the airborne signal (Figure 3-1b) and was comprised of a series of 4-7 impulses per pulse (Figure 32). The mean values of three sets of 20 bursts per measured individual (N=19) were compared for t he following analyses. Pulse interval was positively correla ted with body length (N = 19, F= 17.54, r2 = 0.5078, P =0.0006*, Figure 3-3). The positive relationship between signal interval and body length is a common pattern among other insects (Cocroft and De Luca 2006). Though 21

PAGE 22

pulse interv al was fixed for an individual (s td dev +/0.002ms), bur st rate varied widely from 1 to 40 bursts per sec ond. In bouts of s ound production showing high burst rate, the two-pulse couplet was always produced fa ster (less time bet ween bursts), rather than decreasing the pulse interval within bursts. Identification of the Mech anism of Sound Production. High speed video of individual interacti ons with wings removed showed rapid (1525 cycles/second) anterior-posterior movement of the fused abdominal tergites I and II. During the period of rapid tergal movement s, all other parts of the body remained isolated from movement (including head, m outhparts, legs, and thorax). This form of tergal movement was only observed in the approached individual for the five interactions filmed during the high speed vi deo sessions. The rate of contractions (forward-backward) fell within the typical repetition rate observed when bursts are produced (25Hz). The anterior-posterior mo vement of the tergal plate was not accompanied by any deformation, depression, or folding of the tergit es or corresponding sternites. Because there wa s no deformation or conformational change of the tergal plate during movement and sound pr oduction, I can be fairly certain that the tergal plate does not function as a tymbal to produce si gnals, as has been suggested by previous authors for this and other families in the Pentatomomorpha (Gogal a 1974, 1984, VirantDoberlet and Cokl 2004). SEM images obtained of the undersides of the right and left metathoracic-wings confirmed the presence of a stri dulitrum located on the ventral si de of the costal vein of the metathoracic wing (Figure 3-4). The pos ition of the stridulitrum opposes a raised surface on the dorsal side of abdominal tergite I which, when moved along the observed anterior-posterior field of movement, follows the length of the stridulitrum against the 22

PAGE 23

grain of the stridulitrum teet h (Figure 3-5). Stridulitra we re found in both males and female adults and were absent on the wing pads of nymphs. The experimental loss-of-function manipulat ions suppor ted the hypothesis that the wings act in concert with abdominal tergit es I and II to produce sounds. Experimental removal of the wings followed by the ac oustic analysis revealed that wings are needed to produce high-frequency components of sounds, but not low-frequency components. Metathoracic wing removal eliminated all higher frequency components of signals, and reduced the two-pulse couplet structure to a single low-frequency pulse (0-1000Hz, Figure 3-6), however it did not silence signals completely. Application of wax between the thorax and abdominal tergites I and II successfully silenced individuals by preventing anterior-posterior movement of abdominal tergites I and II. These observations suggest that the high-frequency two-pulse couplet is generated by the forward (first pulse) and backward (second pulse ) movement of the tergal plate against a metathoracic wing stridulitru m. Without wings, the forwar d-reverse movements of the tergal plate no longer generate high-frequency sounds by rubbing against the stridulitrum. The remaining low-frequency pe rcussive signals following wing removal corresponded to the impact of the tergal plate on the posterior edge of the metanotum. Behaviors Associated with Signal Production All sounds recorded took place in a very specific behavioral context: they were exclusive to encounters between two adults of the same species. No mating was observed during the duration of these trials as specimens were collected from nonfeeding, non-mating aggregations. Sounds were only produced by a single interaction participant at the start of a physical encounter between two adults. Sounds were 23

PAGE 24

produced exclusively in this encounter contex t and wer e not made outside of periods of physical contact. The individual that produced sounds, re ferred to here as the signaler, was determined by the relative speed of encounter participants. The signaler was always the individual moving with the least relative velocity (body lengths/s) at the start of the encounter (N=100). The individual moving with the most velocity was always silent. These results suggest that signals are a direct response to approaches by other individuals and are not used in long or short-range mate attraction. Within the specific encounter context described above, certain target behaviors and sex combinations duri ng encounters strongly increased the probability that an encounter produced sounds (Table 3-1). S ounds were produced in 100% of encounters where the approaching individual climbed on top of the signaler (N=19). Approaching males crawled onto other individuals sign ificantly more than approaching females, regardless of the sex of the signaler (N=100, df= 1, chi-sq=9.005, p=0.0035*). Males also crawled onto other males more frequent ly than females. Because all encounters where an individual crawled on top of anot her resulted in sound production by the crawled-on individual, the male bias in cr awling behavior resulted in a male-bias in the sex of approachers during interactions which produced sounds. Signals were also produced much more frequently in encount ers where the approached signaler shook his/her body laterally from side to side, a behavior which occurred more frequently when that individual was crawled up on (N=100, df=1, chi-sq=13.020, P= 0.0062*). The strong association between being crawled upon and body rocking by the signaler suggests that the function of sounds may be to discourage close physical contact. 24

PAGE 25

In the series of arthropod threat enc ounters sounds were never produced in interspecies encounters, between Jadera and cockroaches (N=23) or ants (N=17). There was apparent release of chemical defen se volatiles by each adult which caused the roaches and ants to clean themselves thoroughly. Pinching legs and antennae with forceps did not successfully elicit sounds from any males. Smothering between the thumb and index finger encouraged sound production by all individuals (N=6) so long as constant pressure was applied. Defensive chemicals (toasty almond smell) could be smelled following the smothering treatment. 25

PAGE 26

CHA PTER 4 DISCUSSION I have shown that Jadera haematoloma produces substrate and airborne vibrations using similar morphological tools used by other closely-related Hemiptera in a unique behavioral context. The sounds present ed here show superficial similarity to other Hemiptera that have short stereot yped signals without mu ch signal modulation (Gogala 1984). Jadera haematoloma sounds lack the complex modulation or multiple song types that have been observed in the c ourtship rituals of some Pentatomidae (Cokl et al. 2001) and strongly differ from the continuous, heavily modulated sounds produced by various Cicadidae (Drosopoulos et al. 2006), Membracidae (Rodriguez et al. 2004), and Psyllidae (Percy et al. 2006). The tergal plate and wing-stridulitrum mechanism found in Jadera haematoloma has been observed in several other member s of the Pentatom omorpha; Piesmatidae (Leston et al. 1954, Jorigtoo et al. 1998), two Lygaeid genera ( Piesma and Kleidocerys, Ashlock and Lattin 1963), Cydnidae, and t he Thyreocoridae (Schaefer 1980, Gogala 1974) but is not similar to the tymbal me chanism observed in Homopteran Hemiptera. The stridulation shown here in absence of def ormation of the tergal plate favors the plectrum hypothesis over the tymbal hypothe sis for the role of the tergal plate in vibration production. The Cydnidae, wh ich also possess a metathoracic wing stridulitrum and abdominal pl ectrum, differs from Jadera in sound complexity. Jadera produced only a single repeated burst, wit h fewer discrete harmonics detectable through the substrate, and did not demonstrate the diversity of context-specific songs observed by Gogala and colleagues in the Cydnidae (1974). High-resolution recordings were unavailable for comparisons wit h sounds produced by the Lygaeidae, 26

PAGE 27

Tessaratomidae, Scutelleridae, Thaumastelli dae, and Leptopodidae, which have similar wing and tergal plate morphology. The reco rdings by Gogala (199 0) of adult male Arhyssus hyoscyam i L. (Hemiptera:Rhopalidae) very closely resembled those recorded here; signals were succinct and highly ster eotyped, however the frequency range was much lower than those recorded here (80Hz), potentially an artifact of the recording equipment used. From these observations drawn from the literat ure, it is clear that a shared sound producing mechanism does not nec essarily confer acoustic similarity. The behavioral context of sound production suggests that sounds may be signals in response to an approach by another i ndividual. Sound production began by an individual who was approached by a conspecific moving at greater speed. The specific behavioral context of sound production by J. haematoloma is unique because the sounding role in an encounter is determined by the relative speed of the individual, regardless of its sex. In most Hemipteran communication systems, the signaler role is stereotyped by sex or age as is appropriate signaler identification during courtship and mother-offspring interactions (Cocroft 2001, Cocroft and Rodriguez 2005). Because two adult J. haematoloma are already touching when soun ds are produced, and because it occurs in the absence of offspring, it is clear that sounds are not used as signals to attract conspecifics from a distance or to al ert offspring to threats. On the contrary, increased repetition rates associated with being crawled upon and simultaneous body rocking behavior suggest that sounds are more common in proximate interactions. This could explain the low-modulation and relatively simple repetition of sounds when compared to species which use signaling fo r species recognition or during complex 27

PAGE 28

courtship displays. If individuals ar e in close proximity, the sex, age, quality, and species of the signaler may be tr ansparent to the receiver. All inter-species interactions with ot her arthropods failed to produce sounds. Though handling the insects caused them to produce sound, all other threat stimuli failed to elicit signals. Jadera haematoloma is chemically protected, and may only experience real threat from larger vertebrate predators (Aldrich et al. 1990a, 1990b) which have been shown to respond negatively to aposematism in this species (Ribeiro 1989). These results support the hypothesis that sounds target nearby conspecifics and are not frequently used in interspecies interactions. My exploration of vibrations produced by Jadera haematoloma revealed that the vibration-producing struct ures are similar to other closel y related Hemiptera. The tergal plate plectrum which J. haematoloma uses to produce sounds is shared by several other Heteroptera, supporti ng the hypothesis presented by Schaefer (1993) that the tergal plate plectrum is largely conserv ed in terrestrial Heteroptera with multiple independent origins of wing stridulating struct ures. However, there is still considerable acoustic variation among species using the same mechanism as J. haematoloma. This suggests that while sound producing structur es themselves may be conserved, the sounds do not show phylogenetic signal. In stead, the function of signals and the behavioral context might be more important in shaping signal structure in this group of insects. Further exploration of signal divers ity in target clades, and descriptions of each behavioral context would help to addr ess this exciting question. 28

PAGE 29

29 Table 3-1. Influence of participant sex and behavior on whether or not sounds were produced during an encounter Variable N df 2 p -value Sex signaler sex (M & F approacher) 100 1 6.732 0.0159 signaler sex (M approacher) 59 1 0.299 0.7381 signaler sex (F approacher) 41 1 0.370 1 approacher sex (M & F signaler) 100 1 16.246 <0.0001 *** approacher sex (M signaler) 52 1 6.405 0.0202 approacher sex (F signaler) 48 1 4.396 0.0489 Behavior approacher crawls on approachee 100 1 22.537 <0.0001 *** signaler rocks body 100 1 2.912 0.2430 leg grappling 100 1 0.001 1.000 p-values from Fishers two-tailed test from ch i-squared contingency table against the presence or absence of signals during each encounter (*p<0.05, **p<0.001, ***p<0.0001)

PAGE 30

Figure 3-1. Spectrogram compar ison of airborne (a) and substrate (b) bursts of a male Jadera haematoloma The two-pulse couplet structure of each burst is less apparent in the substr ate-borne vibration. 30

PAGE 31

Figure 3-2. Oscillogram of a single burst showing impu lse structure in a microphone recording. Impulses 1-5 correspond to the first pulse; 6-11 correspond to the second pulse in the burst. 31

PAGE 32

Figure 3-3. Pulse interval, the time betw een the first and second pulse of a burst, is positively correlated with body length. (N = 19, R-sq = 0.5078, p=0.0006*). Triangles are females, circles are males. Figure 3-4. Adult male Jadera haematoloma SEM image of the ventral side of the left metathoracic wing. Arrow indicates st ridulitrum on costal vein; scale bar, 200um 32

PAGE 33

Figure 3-5. Adult male Jadera haematoloma right abdominal tergites I and II. Dashed double-headed arrow indicates field of motion of abdominal segments along anterior-posterior axis, single headed arrow indicates plectrum surface. Th, thorax; scale bar, 200um 33

PAGE 34

Figure 3-6. Spectrograms of bur sts from a male with wings (a, b), and a male with wings removed (c, d). Wing removal abruptly silenced all higher-frequency spectra, and eliminated two-pulse c ouplet structure (b, d) 34

PAGE 35

LIST OF REFERENCES Aldrich, J. R., S. P. Carroll, W. R. Lusby M. J. Thompson, J. P. Kochansky, and R. M. Waters, 1990a. Sapindaceae, cyanolipids, and bugs. J. Chem. Ecol. 16:199210 Aldrich, J. R., S. P. Carroll, J. E. Oliver, W. R. Lusby, A. A. Rudmann, and R. M. Waters. 1990b. Exocrine secretions of scentless plant bugs: Jadera, Boisea and Niesthrea species (Hemiptera: Heteroptera: Rhopalidae). Bioc hem. Syst. Ecol. 18:369-376 Ashlock, P. T., and J. D. Lattin. 1963. Stridulatory mechanisms in the Lygaediae, with a new American genus of Orsillinae (Hemipte ra:Heteroptera). Ann. Entomol. Soc. Am. 56:693-703 Autumn, K., S. T. Hsieh, D. M. Dudek, J. Chen, C. Chitaphan, and R. J. Full. 2006. Dynamics of geckos running vertically. J. Exp. Biol. 209: 260-272 Carroll, S. P., and J. E. Loye. 1987. Specialization of Jadera species (Hemiptera: Rhopalidae) on seeds of s apindaceae (Sapindales), and coevolutionary responses of defense and attack. Ann. Entomol. Soc. Am. 80:373-378 Carroll, S. P., and C. Boyd. 1992. Host race radiation in the soapberry bug: natural history with the history. Evolution. 46:1052-1069. Carroll, S. P., M. Marler, R. Winchell, and H. Dingle. 2003. Evolution of cryptic flight morph and life history differences during hos t race radiation in the soapberry bug, Jadera haematoloma Herrich-Schaeffer (Hemiptera : Rhopalidae). Ann. Entomol. Soc. Am. 96:135-143 Cocroft, R. B. 2001. Vibrational communication and the ecology of group-living, herbivorous insects. Am. Zool. 41:1215-1221 Cocroft, R. B., and R. L. Rodriguez. 2005. The behavioral ecology of insect vibrational communication. Bioscience. 55:323-334. Cocroft, R. B., and P. De Luca. 2006 Size-frequency relationships in insect vibratory signals. pp 99-110. In S. Drosopoulos and M. Claridge (eds.), Insect sounds and communication: physiology, behavior, ecology and evolution. Taylor and Francis Group, Boca Raton, FL. okl. A. 1983. Functional properties of vibroreceptors in the legs of Nezara viridula [L] (Heteroptera: Pentatomidae). J. Comp. Physiol. A. 150:261-269. okl, A., H. L. Mcbrien, and J. G. Millar. 2001. Comparison of substrate-borne vibrational signals of two stink bug species, Acrosternum hilare and Nezara viridula (Heteroptera: Pentat omidae). Ann. Entomol. Soc. Am. 94:471-479 35

PAGE 36

Cornell Lab of Ornithology 2008. Raven interactive sound analysis software v1.3. Cornell Lab of Orni thology, Ithaca, NY Drosopoulos, S., E. Eliopoulos, and P. Tsakalou. 2006. Is migration responsible for the peculiar geographic distribution and spec iation based on acoustic divergence of two cicadas in the Aegean Archipel ago?. pp 219-226. In S. Drosopoulos and M. Claridge (eds.), Insect sounds and communication: physiology, behavior, ecology and evolution. Taylor and Francis Group, Boca Raton, FL. Fisher, R.A. 1922. On the interpretation of chi-s quared from contingency tables, and the calculation of p. J. R. Stat. Soc. 85:87-94 Florida Exotic Pest Plant Council. 2009. FLEPPC 2009 list of invasive plant species Fall 2009. FLEPPC, University of Georgia, Athens, GA. Gogala, M., A. Cokl, K. Dr aslar, and A. Blazevic. 1974. Substrate-borne sound communication in Cydnidae (Heteropt era). J. Comp. Physiol. 94:25-31 Gogala, M. 1984. Vibration producing structures and songs of terrestrial Heteroptera as systematic character. Bioloski Vestnik (Ljubljana). 32:19-36 Gogala, M. 1990. Distribution of low frequency vibrational songs in local Heteroptera Scolopia. 1:125-132 Gogala, M. 2006. Vibratory signals produced by Heteroptera Pentatomorpha and Cimicomorpha. pp 275-295. In S. Drosopoulos and M. Claridge (eds.), Insect Sounds and Communication: physiology, behavior, ecology and evolution. Taylor and Francis Group, Boca Raton, FL. Henry, T. J. 1997. Phylogenetic analysis of family groups within the infraorder Pentatomomorpha (Hemiptera: Heteropt era), with emphasis on the Lygaeoidea. Ann. Entomol. Soc. Am. 90:275. Jorigtoo, N., C. W. Schaefer and J. A. Lockwood. 1998. Stridulatory apparatus of Piesma Le Peletier & Serville (Hemiptera: Pi esmatidae). Ann. Entomol. Soc. Am. 91:848-851 Lawson, F.A, a nd J. Chu. 1971. A scanning electron microscopy study of stridulating organs in two hemiptera. J. Kansas. Entomol. Soc. 44:245-253 Leston, D., J. G. Pendergrast, and T. R. E. Southwood. 1954. Classification of the terrestrial Heteroptera (Geocorisae). Nature. 174:91. Mankin, R. W., J. Brandhorst-Hubbard, K. L. Flanders, M. Zhang, R. L. Crocker, S. L. Lapointe, C. W. McCoy, J. R. Fisher, and D. K. Weaver. 2000. Eavesdropping on insects hidden in interior structures of plants. J. Econ. Entomol. 93:1173-1182. 36

PAGE 37

Mankin, R. W., D. Shuman, and J. A. Coffelt. 1996. Noise shielding of acoustic devices for insect detection. J. Econ. Entomol. 89:1301 Masters, W.M. 1979. Insect disturbance stridulation: its defensive role. Behav. Ecol. Sociob iol. 5:187-200 Numata, H., K. Masahiro, F. Hisashi, and T. Hidaka. 1989. Sound production in the bean bug, Riptortus clavatus Thunburg (Heteroptera: Alydidae). Appl. Ent. Zool. 24:169-173 Percy, D.M., G.S. Taylor, and M. Kennedy. 2004. Psyllidae: acoustic diversity, mate recognition, and phylogenetic signal Invertebr. Syst. 20:431-445 Photron Limited. 2006. Photron Fastcam Viewer for high speed digital imaging. Photron Limited, SanDiego, CA Polhemus, J.T. 1994. Stridulatory mechanisms in aquatic and semiaquatic Heteroptera. J. New York. Entomol. S 102:270-274 Ribeiro, S.T. 1989. Group effects and aposematism in Jadera haematoloma (Hemiptera: Rhopalidae). Ann. Entomol. Soc. Am. 82:466-475 Rodriguez, R.L., L.E. Sullivan and R. B. Cocroft. 2004. Vibrational communication and reproductive isolation in the Enchenopa binotata species complex of treehoppers (Hemiptera: Membracidae). Evolution. 58:571-578 SAS Institute Inc. 1989-2008. JMP Statistical Computi ng Software, v. 2.0. SAS Institute Inc., Cary, NC Schuh, R. T. and J. A. Slater. 1995. True bugs of the world (Hemiptera: Heteroptera). Cornell University Press, Ithaca, NY Schaefer, C.W. 1980. The sound producing structures of some primitive Pentatomoidea (Hemiptera:Heteroptera). J. New York. Entomol. S 88:230-235 Schaefer, C. W., and R. T. Pupedis. 1981. A Stridulatory Device in Certain Alydinae (Hemiptera:Heteroptera:Alydidae). J. Kansas. Entomol. Soc. 54:143-152 Schaefer, C.W. 1993. Origins of the New World Rhopalinae (Hemiptera: Rhopalidae) Ann. Entomol. Soc. Am. 86:127-133. Shaw, S. R. 1994. Detection of airborne sound by a cockroach vibration detector: a possible missing link in insect auditory evolution. J. Exp. Biol. 193:13-47. Slater, J. A., and R. M. Barankowski. 1978. How to know the true bugs (HemipteraHeteroptera). William. C. Brown Company, Dubuque, IA 37

PAGE 38

38 Tishechkin, D.Y. 2006. Acoustic characters in the cla ssification of higher taxa of Auchenorrhyncha (Hemiptera). pp 99-110. In S. Drosopoulos and M. Claridge (eds.), Insect sounds and communication: physiology, behavior, ecology and evolution. Taylor and Francis Group, Boca Raton, FL. Virant-Doberlet, M., and A. Cokl. 2004. Vibrational communication in insects. Neotrop. Entomol. 33:121-134 Wenninger, E. J., D. G. Ha ll, and R. W. Mankin. 2009. Vibrational communication between the sexes in Diaphorina citri (Hemiptera: Psyllidae). Ann. Entomol. Soc. Am. 102:547-555. Waite, J.K. and J. S. Hwang. 2002. Pests of litchi and longan. pp. 331. In J.E. Pena, J.L. Sharp & M. Wyso ki (eds.), tropical fruit pes ts and pollinators: biology, economic importance, natural enemies and control. CAB International Oxford, Oxford, UK.

PAGE 39

BIOGRAPHICAL SKETCH Ariel grew up in Portland, OR where she spent summers attending OMSI science camp, birding, camping with her parents, and volunteer ing at the Or egon Zoo. Ariels parents generously allowed a diversity of pets in to their home, which included at various times cats, dogs, mice, lizards, snakes, new ts, and a very large frog named Wilbur. These experiences helped generate a lifelong interest in ecology, conservation, and animal behavior. She attended Cornell Univ ersity to study biology and entomology. While at Cornell, she met her futu re husband and adventure buddy Noah, and began her research career studying snail parasites and social arachnid behavior. Ariel graduated from Cornell cum laude in 2007 with distinction in research. Following graduation, Ariel spent a year assisting with conservation research all around the country, and traveling to interesting plac es like Wisconsin and Ecuador for fun. She enthusiastically started her graduate studies at the University of Florida in fall of 2008. Future studies will be publ ished under her married name, Ariel Frances Zych. 39