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Estivation in the sirenid salamanders, Siren lacertina (Linnaeus) and Pseudobranchus striatus (Le Conte)

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Estivation in the sirenid salamanders, Siren lacertina (Linnaeus) and Pseudobranchus striatus (Le Conte)
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Etheridge, Kay, 1954-
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v, 67 leaves : ill. ; 28 cm.

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Subjects / Keywords:
Amphibians ( jstor )
Animals ( jstor )
Estivation ( jstor )
Moisture content ( jstor )
Salamanders ( jstor )
Sirens ( jstor )
Soil water ( jstor )
Soil water content ( jstor )
Soils ( jstor )
Species ( jstor )
Dissertations, Academic -- Zoology -- UF
Dormancy (Biology) ( lcsh )
Salamanders ( lcsh )
Sirenidae ( lcsh )
Zoology thesis Ph. D
City of Gainesville ( local )
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bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 1986.
Bibliography:
Bibliography: leaves 62-66.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Kay Etheridge.

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ESTIVATION IN THE SIRENID SALAMANDERS,
SIREN LACERTINA (LINNAEUS) AND
PSU=o RANCHUSSTRIATUS (LE CONTE)





BY





KAY ETHERIDGE


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


1986




ESTIVATION IN THE SIRENID SALAMANDERS,
SIREN LACERTINA (LINNAEUS) AND
PSEUDBRANCHiJ'S'STRIATUS (LE CONTE)
BY
KAY ETHERIDGE
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1986


ACKNOWLEDGMENTS
I would like to thank several people for their invaluable
assistance during this study. Marty Crump, my major advisor, has been
a great help throughout my studies, and her encouragement and common
sense advice have helped me over many obstacles. John Anderson, David
Evans, Harvey Lillywhite, Frank Nordlie and Michele Wheatly not only
gave me guidance and technical assistance, but also trusted me with
their equipment. Archie Carr and Walter Judd have advised me during
this study and have reviewed this dissertation. Mark Seyfried helped
me comprehend soil physics, and Lou Guillette introduced me to the art
of histology. Chip Oglesby, Allison Rogers and Sam Ward, who
volunteered their time through the undergraduate research assistant
program, were a tremendous help during one of the most labor intensive
portions of this study. Don Banknight helped supply many of the
salamanders used in this study.
I am grateful to many of the faculty, staff and graduate students
of the Department of Zoology for their assistance in innumerable
facets of this study. Financial support for this work was from the
Department of Zoology and a Sigma Xi Grant-in-Aid of Research.
Finally, I wish to thank my family and friends for their support
during my studies.
ii


TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
ABSTRACT iv
CHAPTERS
I INTRODUCTION 1
Background 1
Study Animals and Habitat 3
Objectives 5
II THE ENERGETICS OF ESTIVATION 9
Introduction 9
Materials and Methods 10
Resul ts 13
Discussion 23
III WATER BALANCE DURING ESTIVATION 33
Introduction 33
Materials and Methods 37
Resul ts 40
Discussion 47
IV SUMMARY AND CONCLUSIONS 56
LITERATURE CITED 62
BIOGRAPHICAL SKETCH 67
i i i


Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
ESTIVATION IN THE SIRENID SALAMANDERS,
SIREN LACERTINA (LINNAEUS) AND
PSEUDOBRANCHUS SRIATUS (LE CONTE)
BY
KAY ETHERIDGE
December, 1986
Chairman: Martha L. Crump
Major Department: Zoology
Siren lacertina and Pseudobranchus stria tus are aquatic
salamanders that inhabit drought-prone waters in the southeastern
United States. When drought occurs, sirenids burrow into the
substratum and remain inactive until the habitat is reflooded. This
study investigated adaptations that allow these two species to survive
drought.
Siren lacertina and P. stria tus were induced to estivate in the
laboratory and several parameters were measured: rates of metabolism,
blood lactate levels, ventilation rates, rates of water exchange with
soil, urinary bladder volumes and solute concentrations of plasma and
urine. In addition, lipids stores were measured in animals from
aquatic populations, and the cocoon of an estivating S_. lacertina was
examined by light microscopy.
In both species resting metabolic rates are 60 to 70% lower in
estiva tors than in aquatic animals. At these low metabolic rates
iv


adult S. lacertina can survive two to three years without food.
Smaller lacertina and P_. stria tus have higher mass-specific
metabolic rates during estivation, but even a 1 g sirenid can survive
for several months on stored energy. Ventilation rates decrease
during estivation, but low blood lactate levels indicate that
respiration is aerobic.
The cocoon is composed of dead squamous epithelial cells. This
layer does not block water movement and estivating sirenids exchange
water with the soil. The rate of water exchange with the soil
increases with a decrease in body size. Rate and direction of water
exchange are also related to the water potential of the soil.
Estiva tors maintain a positive water balance in soil with water
potential greater than -5 bars, but begin to lose water in drier soil.
Siren lacertina store dilute urine in their bladder; the mass of
this urine may be the equivalent of as much as 10% of their body
mass. Plasma concentrations of sodium, potassium and chloride are
similar in aquatic animals and estivators; however, plasma urea
concentrations are six times higher in estivators. Due to urea
accumulation, plasma osmolality is higher in estivators than aquatic
animals. This lowers the water potential of estivators and decreases
the rate at which they will lose water in very dry soil.
v


CHAPTER I
INTRODUCTION
Amphibians and reptiles can be described as low energy systems in
comparison to birds and mammals, which could be called high energy
systems (Pough 1983). This comparison relates to the fact that lower
vertebrates are primarily ectothermic and expend little energy for
maintenance of body temperature. Therefore, reptiles and amphibians
have low rates of energy intake and expenditure relative to birds and
mammals, which fuel their high metabolic rates with high rates of
energy intake. Differences in rates of energy flow have several
consequences, one of which is the frequency at which an animal must
"refuel." High energy systems require a constant source of food; low
energy systems can rely on a more variable supply. Under adverse
conditions most ectotherms can reduce their energy costs and remain
inactive for prolonged periods until conditions improve. Some birds
and mammals can lower their energy demand for short periods (torpor)
or seasonally (hibernation), but they cannot begin to approach the
length of time that ectotherms can remain inactive. The ability of
ectotherms to remain dormant for long periods allows them
opportunities to exploit transient or ephemeral resources that would
not support a high energy endotherm.
Energy may not be the only limiting resource, however, and lack
of water can restrict the use of some environments. Of all the
1


2
tetrapod vertebrates, amphibians appear to be the most closely tied to
moist or aquatic habitats. Most amphibians have an aquatic larval
stage and skin that offers little resistance to water loss; hence,
they seem to be ill-adapted for survival in a dry environment.
Nevertheless, several species of anurans and a few salamanders do live
in xeric habitats; some examples are Amby stoma ti grin urn (Del son and
Whitford 1973), Scaphiopus multipiicatus and S. couchii (Ruibal et al.
1969), Heleioporus eyreia (Bentley et al. 1958), Limnodynastes
spenceri, Neobatrachus pictus and several species of Cyclorana (Lee
and Mercer 1967). Typically, these animals are terrestrial, nocturnal
species that spend most of their adult lives in underground burrows,
surfacing to feed and breed for relatively brief periods when water is
available. In addition to behavioral adaptations these amphibians
have in common several physiological adaptations that permit this type
of life history. As is the case with other ectotherms, their
metabolic costs are low, and they can survive long periods of
estivation on stored energy (e.g., van Beurden 1980). This type of
strategy has been most thoroughly studied for several species of
Scaphiopus, the spadefoot toads (Ruibal et al. 1969; Seymour 1973c;
McClanahan et al. 1976). Most studies of amphibian estivation have
focused on terrestrial or semi-aquatic anurans. However, one aquatic
anuran, Xenopus laevis (Balinsky et al. 1967), and one family of
aquatic salamanders, the Sirenidae, are known to estivate when their
habitats dry up. Little is known concerning the effects of drought
upon aquatic amphibians. This study focused on the adaptations that
enable sirenid salamanders to survive prolonged drought.


3
Study Animals and Habitat
All three species in the family Sirenidae are indigenous to
shallow water habitats in the southeastern United States. The two
species investigated in this study were the greater siren, Siren
lacertina Linnaeus, which ranges from the District of Columbia south
to the tip of Florida, and the dwarf siren, Pseudobranchus striatus Le
Conte, which is found from southern South Carolina to the eastern half
of the Florida panhandle, and south to the tip of Florida (Conant
1975). The third species in the family, which is not included in this
study, is the lesser siren, S. intermedia Le Conte. These species are
similar in habitat and morphology, but are dissimilar in size; P_.
striatus rarely exceeds 25 cm in length, whereas lacertina may
reach almost 1 m.
Little is known about the life history of these secretive,
nocturnal salamanders. Reproduction occurs in late winter or early
spring and females deposit eggs singly or in pairs on submerged
aquatic vegetation (Goin 1941; Davis and Knapp 1953; U1tsch 1973).
Siren ingest large amounts of plant material along with prey items
such as crustaceans, mollusks and insect larvae, but it is not known
whether or not Siren digest cellulose (Davis and Knapp 1953; Burch and
Wood 1955; U1 tsch 1973; Hanlin 1978). Plant material has not been
reported in the gut of P_. striatus, but dwarf sirens do eat small
crustaceans and insect larvae (Freeman 1967). Sirenids may be among
some of the most productive salamanders; Gehlbach and Kennedy (1978)


4
found that S. intermedia was the dominant vertebrate species in a
Texas beaver pond, due in part to its great fecundity (151-226
eggs/female'year) and rapid growth to sexual maturity in one year.
This study was conducted from 1981 through 1986 in the vicinity
of Gainesville, Florida, where all three species occur sympatrically
in an array of aquatic habitats that vary in degree of permanency.
For example, all three species have been found both in the River Styx,
a permanent body of water, and in drought-prone ponds on Paynes
Prairie, Alachua County, Florida (A. Carr, pers. comm.). Typical
sirenid habitat in this area is characterized by shallow, soft-bottom,
weed-choked waters. One of the most common aquatic plants is the
introduced water hyacinth, Eichhornia crassipes, and sirenids are
often found in close association with the root systems of these
abundant floating plants. This type of habitat is uninhabitable for
many aquatic vertebrates because weed-choked waters are usually
hypoxic and hypercapnic (Ultsch 1976a), and are often transient
resources. Shallow aquatic habitats periodically dry out or change
with succession to a terrestrial environment, and survival of the
inhabitants is dependent upon an ability to withstand dehydrating
conditions, or an ability to move to new suitable habitat.
No evidence has been reported to suggest that sirenids migrate
overland in times of drought to seek new aquatic habitats. Instead,
they estivate during dry conditions by burrowing into the soil and
remaining inactive until the habitat is reflooded (Cockrum 1941;
Freeman 1958; Reno et al. 1972; Gehlbach et al. 1973). In the area of


5
this study drought can occur at any time of the year. Over a 70 year
period the summer months had the highest mean rainfall; however, in
1983 and 1984 there were summer droughts (Fig. 1-1). During this
study drought also occurred in winter and spring. Although the term
estivation was originally defined as summer inactivity (from the Latin
for summer, aestas), it also has traditional associations with
inactivity due to drought and is used in that sense here. Although
the ability to estivate permits these aquatic salamanders to colonize
potentially transient bodies of water, little is known about the
physiological mechanisms involved in estivation.
Objectives
This study centers on two species of sirenid salamanders (Siren
lacertina and Pseudobranchus stria tus) that serve as excellent models
for the study of estivation in amphibians; both species are aquatic,
but live in habitats susceptible to drought. Aquatic amphibians are
subjected to several stresses as their habitats dry up, including
dehydration, starvation and the accumulation of nitrogenous wastes
that are normally excreted in water. The objectives of this research
were to examine the adaptations used by sirenids to cope with these
stresses and to compare the abilities of these two species to survive
drought. These comparisons are important primarily because of the
size differences between these two species. Individuals of both
species were induced to estivate in the laboratory and, using a range
of sizes within each species, two major areas were investigated.


FIG. 1-1. Average monthly rainfall (cm) in the Gainesville, Florida, area, based on data from the
Agronomy Department, University of Florida, Gainesville, Florida. The solid bars
indicate the 70 year average, the striped bars indicate data from 1983, and the open
bars indicate data from 1984.


28
26
24
22
20
1 8
16
14
12
10
8
6
4
2
MONTH


8
Energetic Costs of Estivation
By measuring oxygen consumption during estivation, energy
expenditure was calculated and then compared to rates of energy
consumption in nonestivators. In addition, seasonal fluctuations in
energy stores available for use during estivation were measured by
extracting lipids from animals collected bimonthly throughout the
year.
Water Balance During Estivation
Rates of water loss and gain in soil were measured to determine
the effect of body size and soil water content on these rates. Plasma
and urine samples were analyzed to examine the effects of estivation
on ion concentrations and nitrogenous wastes.
Data from this study were used to determine adaptations used by
sirenids to survive drought and also allowed estimation of the length
of time different size classes can survive without standing water.
Finally, the responses of these aquatic animals to drought were
compared to those of terrestrial amphibians that estivate.


CHAPTER II
THE ENERGETICS OF ESTIVATION
Introduction
Because estivating animals are inactive and do not feed, they
must rely on stored energy for an unpredictable amount of time.
Potential survival time is dependent in part upon the quantity of
stored energy available to the estiva tor at the onset of estivation
and the rate at which this store is depleted. In amphibians, as in
most animals, energy stored as lipid tends to vary with body size, sex
and time of year (Rose 1967; Brenner 1969, Byrne and White 1975;
Fitzpatrick 1976; Morton 1981). Resting metabolic rates in amphibians
also vary with several factors, particularly temperature and body
size. Furthermore, in estivating lungfish (Delaney et al. 1974) and
anurans (Seymour 1973c; Loveridge and Withers 1981; van Beurden 1980;
McClanahan et al. 1983) resting metabolic rates are 50-70$ lower than
rates of nonestivators at the same temperatures.
In this part of the study the energetics of sirenid estivation
were investigated. Lipid content was measured in adult Siren
lacertina throughout a year to determine whether fat stores vary
seasonally, for if they do the timing of drought could affect survival
time. Metabolic rates were measured to estimate the potential amount
of time sirenids could survive before depleting stored energy and to
determine if metabolic rates could be reduced below resting levels.
9


10
In addition, the effect of body size on potential survival time was
studied by comparing the metabolic rates of adult and juvenile _S.
lacertina and Pseudobranchus striatus over a range of body sizes.
Materials and Methods
Metabolic Rates
Siren lacertina and Pseudobranchus striatus were collected from
ponds, rivers and lakes around Gainesville, Florida. Large S_.
lacertina were caught in a dipnet or on a hook and line using beef
heart as bait. Smaller animals were caught using a hand-held
dredge. Animals that were used for measurements of oxygen consumption
were held in water-filled aquaria for two weeks before estivation was
induced and were not fed during this period or during the experiment.
Both S. lacertina and P_. striatus were induced to estivate in the
laboratory at various times throughout the year. Animals were weighed
and placed individually into containers that held soil saturated with
water. Container size and soil depth varied with animal size;
containers were large enough to allow the salamanders to extend to
their full length, and soil depth was approximately four times the
body diameter of the animal. After animals burrowed into the soil,
the soil was allowed to dry slowly. Water was added as necessary to
maintain soil water content between 6 and 122 by mass. Estivating
animals were kept at 23C, the mean annual soil temperature at 10 cm
depth in the area of Gainesville, Florida (based on data from the
University of Florida Agronomy Department).


11
Rates of oxygen consumption (V, ) were measured at one- to two-
u2
week intervals early in estivation and at one-month intervals after 50
days in estivation. For each point during estivation, sirenids
representing a range of body size were carefully excavated from their
burrows and weighed. Metabolic measurements were made for 53
individuals, ranging in mass from 0.9 g to 1061 g. Oxygen consumption
of animals smaller than 20 g was measured using a Gilson respirometer
and standard stoichiometric techniques. Oxygen consumption of larger
animals was measured using a flow-through system. Each animal was
placed in a plastic tube slightly larger than its body dimensions.
This tube was sealed except for incurrent and excurrent air ports at
opposite ends. A pump was used to draw air sequentially through the
tube, a column of soda lime to remove CO2, a column of silica gel to
remove water and an Applied Electrochemistry Oxygen Analyser Model
S-3A, to measure the fraction of oxygen in the air sample. Rates of
oxygen consumption were calculated using equations given by Withers
(1977) and were corrected to standard temperature and pressure
(STPO). All measurements were made during the animals' inactivity
periods, between 0800 and 1300 h. Handling of animals in an
estivating state had negligible effect. After the animal had spent
one to two hours in the metabolic chamber the rate of oxygen
consumption was stable enough to be measured. Rates of oxygen
consumption were measured at 23C for all estivating sirenids. To
estimate for estiva tors, rates of oxygen consumption were measured
at 23C and 32C for seven S. lacertina (404 to 733 g) that had been
in estivation for more than four months.


12
Blood lactate levels were measured for estivating S_. lacertina to
determine if anaerobic metabolism was an important component of the
energy budget of these animals. Eight adult salamanders that had been
estivating for seven or more months were excavated and anesthetized
with sodium brevitol (0.01 mg/g). Blood was collected by cardiac
puncture, using a heparinized syringe and 23 gauge needle. Whole
blood was diluted 1 to 2 in 8% perchloric acid to precipitate proteins
and then centrifuged. Samples were analyzed for lactate content using
a colorimetric assay from Sigma Diagnostics.
Ventilation rate was measured in 15 animals at several intervals
during estivation. If an animal was positioned in a flow-through
chamber such that its mouth was near the excurrent port, ventilation
could be detected by a rapid and extreme change in the fraction of
oxygen in the excurrent air. This could be measured accurately only
for large animals.
Lipid Stores
In 1984 eight to ten adult S_. lacertina were collected bimonthly
from Orange Lake, Alachua County, Florida, and frozen for later
analysis. Orange Lake is a relatively permanent body of water;
therefore, lipid stores of these specimens were not affected by
periodic droughts. In March of 1986 nine juvenile S_. lacertina (3.6
to 25.5 g body mass) were collected and frozen. Unfortunately, it was
impossible to collect significant numbers of juveniles year round.
Animals were later thawed, weighed, macerated in a tissue homogenizer
with 70 ethanol and dried to a constant mass. The dry tissue was


13
weighed and each sample was extracted several times with petroleum
ether at 35C to remove all lipids (Martof 1969). Samples were dried
once more and reweighed. Total body lipid content was calculated for
each animal by subtracting lean dry mass from total dry mass.
Results
Sirenids that were induced to estivate behaved similarly
regardless of size, species or time of year. When placed in saturated
soil, they burrowed into the substratum using their snout as a
shovel. As long as the soil was saturated with water, each animal
kept its mouth in contact with the surface, but as the soil dried the
salamanders retreated into the burrow formed by their body
movements. In some cases an opening was maintained with the surface,
but in several containers the opening collapsed and was filled as the
soil dried. Animals survived for several months in soil regardless of
whether burrows were open or closed. When they were removed for
metabolic measurements, the salamanders often made a sudden jerky
movement, emitted a yelping sound and ventilated by gulping three or
four times. All animals became still soon after handling ceased.
During estivation the gills atrophied and the entire body of an
estiva tor became covered with layers of dead epithelial cells.
Metabolic Rates

The mass-specific rate of oxygen consumption (Vn /M)
u2
was inversely correlated with body size (y = -11.37x + 50.4,
2
r = 0.7992; Fig. 2-1). Mass-specific metabolic rate


FIG. 2-1. Rate of oxygen consumption (pi Oo/g'h STPD) of estivating P_. striatus (open circles)
and S. lacertina (closed circles) of different body mass. All measurements were made
at 23C between day 25 and day 30 of estivation.


LOG MASS (g)
RATE OF 02 CONSUMPTION Oil 02/g-h)
ST


16
(Vn /M) decreased with time in estivation for sirenids of all sizes
2
(Figs. 2-2, 2-3, and 2-4). Time of year had no effect on metabolic
rate during estivation. The effect of sex on metabolic rate is
unknown because it was difficult to determine the sex of individuals
externally. Larval S_. lacertina (under 2 g mass) had rates of oxygen
consumption that appeared similar to rates of P_. stria tus of similar
body size (Fig. 2-2); however, the sample sizes were too small for
statistical comparison. By day 60 of estivation, the Vn /M for these
smallest sirenids had decreased to 24.5 1.2 ul 02/g*h (mean S.E.),
a reduction of 562 from the mean rate of 53.6 2.4 ul 0£/gh at day

18. A similar decrease in Vn /M was seen in the other size groups of
u2
estivating sirenids. Juvenile sirenids (6-110 g) measured near day 60

of estivation had a mean V~ /M (18.0 3.0 ul 0£/g*h) that was 59.72
2
lower than the mean rate during the first two weeks of estivation
(44.7 5.8 ul 02/g*h). Mean VQ /M of adult S_. lacertina measured
over the same two month interval decreased 63.92 (from 30.5 5.9 ul
02/g*h to 11.0 0.7 ul 02/g*h). In all size classes the greatest

decline in Vn /M occurred during the first two months of estivation
u2
and leveled off with only a slight decrease thereafter.

The Q10 (mean S.E.) for VQ /M in estivating S_. lacertina was
2.1 0.1 for seven animals measured at 23C and 32C. Whole blood
lactate levels in estivating S_. lacertina were low (0.58 0.13
mmol/1; mean S.E.), indicating that metabolism in these animals was
predominantly aerobic. Ventilation rate decreased from 5 to 12
breaths per hour during the first week of estivation, to one or less
breaths per hour by day 300.


FIG. 2-2. Rate of oxygen consumption (STPD) of estivating P_. stria tus (closed circles) and larval
S. lacertina (open circles) weighing less than 5 g. Measurements were made at 23C.


00


FIG. 2-3. Rate of oxygen consumption (STPD) of estivating juvenile^. lacertina weighing 6-
110 g. Measurements were made at 23C.


60
3
Z 40
O
H
Ql
LU
I-
<
oc
0
40 80 120
NUMBER OF DAYS IN ESTIVATION
l>0
o
0
I
160


FIG. 2-4. Rate of oxygen consumption (STPD) of estivating adult S_. lacertina weighing 282-
1061 g. Measurements were made at 23C.


RATE OF 02 CONSUMPTION Oil 02/g-h)
NUMBER OF DAYS IN ESTIVATION


23
Lipid Stores
Lipid stores varied seasonally in adul t S_. lacertina (Fig.
2-5). Females had the largest percentage of dry mass as lipid in the
fall whereas fat stores of males peaked in the summer. Both sexes had
the lowest total body lipid content from January through March. The
total body lipid content expressed as a percentage of dry mass for all
adult animals examined (n = 56) was 7.6 1.0 (mean S.E.). Mean dry
mass in these animals was 20.4% of total wet mass; therefore, average
lipid content was 1.6% of wet mass. Juvenile S_. lacertina collected
in March had a total body lipid content of 5.4 1.8% (mean S.E.);
this amount was not significantly different from that of adults
collected during the same month (2.7 0.6%; t = 1.51, p > .05).
Discussion
Sirenid salamanders conserve energy during drought-triggered
estivation by becoming inactive and by substantially reducing their
metabolic rate. Aquatic Siren and Pseudobranchus are capable of
trimodal respiration, exchanging gases across branchial, cutaneous and
pulmonary respiratory surfaces. The partitioning of gas exchange in
aquatic sirenids is dependent upon body size, ambient gas tensions,
temperature and the activity level of the animals (Guimond and
Hutchison 1973; U1tsch 1976b; Wakeman and U1tsch 1976). In Florida,
typical sirenid habitats are shallow, plant-choked waters that are
often hypoxic and hypercapic. Under these conditions, sirenids rely
largely upon their lungs for both 0^ uptake and removal of


FIG. 2-5. Seasonal changes in total body lipids (mean percentage of dry mass) of adult S_.
lacertina collected bimonthly. Females are represented by open circles and males by
closed circles. Bar length represents two standard errors of the mean.


CO
CO
<
30 -
>-
CO
a
Li.
O
*
CO
g
GL
_l
>-
Q
O
m
_i
<
f
o
20-
10-
Pi
?
4
i 1 1 r
Nov Jan March May
MONTH
I
r\j
<_n
r~
July
r~
Sept


25
COp (Guimond and Hutchison 1973; 111 tsch 1975a). The lungs of S_.
lacertina are nearly two-thirds of the body length and are septate and
infolded, thus providing a large respiratory surface area (Guimond and
Hutchison 1973). These effective lungs provide for gas exchange when
sirenids retreat into the substratum during drought. While the soil
is still saturated with water, these salamanders must breathe at the
surface, but as the soil dries the animals can retreat deeper into the
substratum. Because the gills atrophy during estivation and the layer
of dead epithelial cells covering the body probably impedes cutaneous
respiration, the lungs may become the primary site of gas exchange.
In very porous soil, such as sand or sandy loam, interstitial spaces
allow sufficient gas diffusion such that an opening to the surface
need not be maintained. Seymour (1973b) found that gas concentrations
in sandy soil next to buried spadefoot toads were close to atmospheric
levels even at a depth of 70 cm. Sirenids estivating in the
laboratory at 23C did not need an opening to their burrows; however,
at higher temperatures or in less porous soil an opening to the
surface may be needed for gas exchange.
Estivating sirenids move very little unless they are disturbed by
handling. Most estiva tors moved suddenly when touched and then became
motionless again, but few attempted to crawl away. These animals
appeared to be in a state of light torpor similar to that described
for the estivating lungfish Protopterus aethiopicus (Delaney et al.
1974) and for estivating mammals (Hudson and Bartholomew 1964). This
ability to respond to external stimuli during estivation could aid in


27
avoidance of predation, particularly because sirenids often couple
their sudden jerky movements with a startling yelping noise.
The rates of oxygen consumption measured at the onset of
estivation are close to the resting rates measured by Ultsch (1976a)
for aquatic S_. lacertina and P_. stria tus of the same body size. The
metabolic rates of sirenids of all sizes decline gradually during the
first two months of estivation and then reach a plateau that is 60 to
70% lower than the rate at the onset of estivation. Gehlbach et al.
(1973) measured V /M at 25C in aquatic and estivating S_. intermedia
U2
from Texas, but they reported rates that were nearly three times as
high as those of estiva tors measured in this study and aquatic animals
measured by Ultsch (1976a). It is possible that these S_. intermedia
were not at rest when rates of oxygen consumption were measured.
Even though ventilation rates decreased dramatically as
estivation proceeds, lacertina relied primarily on aerobic
pathways. Mean blood lactate levels for estivating S_. lacertina (0.58
0.13 mmol/1) were similar to those of Scaphiopus hammondii resting
on the surface (Seymour 1973c).
Several species of frogs and a species of lungfish that estivate
in response to drought show a decrease in metabolic rate similar to
that of sirenids (Table 2-1). The rate of this decline varies among
these species. In the frog Lepidobatrachus llanensis VA /M drops
2
nearly 80% after only seven days of dormancy (McClanahan et al. 1983),
whereas a drop of 32% is evident after 25 days in dormant Scaphiopus
couchii (Seymour 1973b). These differences may reflect different
environmental conditions in the habitats where these species occur, or


23
TABLE 2-1
Oxygen Consumption Rates of Estivating Amphibians
and Lungfish (Protopterus) at 23-25C

Minimum VQ /M
during Dormancy
(yl 02/g*h)
Species (Mass)
Resting V /M
2
(yl 02/g*h
Reference
Lepidobatrachus
llanensis
("52-11$' g)
97
20
McClanahan et al.
1933
Pyxicephalus
adspersus
TT!FI3~g)
37
10
Loveridge and
Withers 1980
Scaphiopus
couchi
51
11
Seymour 1973a
(x=20 g)
Cyclorana
platycephal us
156
45
van Beurden 1980
(x=14 g)
Protopterus
aethiopicus
(4100 kg)
25
5
Oelaney et al. 1974


29
differences in the way that estivation/dormancy was induced in these
separate studies. Rate of dehydration, for example, could affect the
time frame of a change in metabolic rate. Unfortunately, the
physiologial mechanisms involved in the reduction of metabolic rate in
these dormant ectotherms are unknown. Although starvation alone has
been shown to reduce the metabolic rate of many vertebrates including
reptiles (Benedict 1932; Belkin 1965), lungfish (Delaney etal. 1974)
and frogs (Hill 1911), the pathways that mediate this effect are
unclear. Even less is known about the direct effects of desiccation
upon metabolism. Changes in the metabolic rate of estivating sirenids
may be related to thyroid function. Siren lacertina that had been
estivating for eight months had circulating levels of thyroxine that
were significantly lower than the plasma thyroxine levels of active
animals (Etheridge, unpublished data). However, no experimental
evidence exists to indicate that the reduction in metabolic rate seen
in estiva tors is thyroid mediated.
One common thread appears in the comparison of V /M of
U2
estivating amphibians and lungfish; the minimum Vn /M during dormancy
U2
for each species is similar (Table 2-1). When the data for each
species are adjusted for body size and temperature, the
minimum V /M of estivators is between 10 and 20 ul Oo/gh for each
u2
species. Resting V~ /M for the same group of species varies much
u2
more, ranging from 37 to 150 yl O2/g*h. This consistency of the
lowest V, /M may indicate that these rates represent the minimum cost
2
of existence for these ectotherms. In these animals resting metabolic
rates appear to be the "idling speeds" when resources (i.e., food and


30
water) are abundant. In animals that become dormant these idling
speeds" can be reset 60-80% lower.
The amount of time an animal can survive without food is
dependent upon its rate of energy consumption and upon the amount of
stored energy the animal can utilize. For estivating sirenids the
most important determinants of metabolic rate are body size, length of
time in estivation and body temperature. The energy stores of each
animal will vary with time of year and possibly with body size.
The number of days estivating sirenids could survive without food
was estimated by calculating energy stores and rates of energy
consumption for animals of various sizes and lipid content (Table
2-2). The higher mass-specific metabolic rate of the sinaller
salamanders results in a more rapid depletion of stored energy than in
the larger animals. A 1 g animal would deplete its energy reserves
1.5 times as fast as a 500 g animal even if both began estivation with
the same body composition (Table 2-2). Increasing environmental
temperatures would cause more rapid depletion of energy stores;
conversely, lower burrow temperatures would prolong the length of time
an animal could estivate. The Q1q of estivating S_. lacertina (Q^ =
2.1) is essentially the same as that reported by Guimond and Hutchison
(1973) for aquatic S_. lacertina (Q-^g = 2.2).
Differences in total body lipid stores at the onset of estivation
would also contribute to differences in potential survival time. The
greater total caloric content of a 500 g S_. lacertina with lipid
stores totaling 20% of its dry mass (the mean lipid content for
females in fall) would allow it to survive 40 days longer without food


TABLE 2-2
Energetics of Estivation in Sirenid Salamanders (at 23C)
An ima1
Wet Mass
(g)
Dry Lipid
mass (g)
Dry Lean
mass (g)
Energy
Availabled
Energy
Costsd
Potential
Survival
KCAL
Lipids
KAL
Lean
Day 1-60
KCAL/Day
After Day 60
KCAL/0ay
Number
Days
Ia
1
0.01
0.18
0.1
0.4
0.004e
0.003e
146
2b
500
7.8
94.2
57.5
197.8
0.961f
0.607f
386
3C
1125
86.0
134.0
877.4
324.5
2.160f
1.366f
842
NOTE: Ory mass averaged 20.4$ of wet mass for freshly caught sirenids.
a Hypothetical sirenid representing the smallest size class (P_. striatus and larval lacertina).
For comparative calculations, lipid content is assumed to be 7.6% of dry mass.
b Hypothetical adult S_. lacertina assumed to have mean lipid content of 7.6%.
c Based on data from an individual female caught November 1984. This animal had a total body lipid
content that was 43% of its dry weight.
d Assumptions: 1. Maximum lean tissue metabolized is 50%; maximum lipid metabolized is 80% (Martof
1969). .
2. Oxidation of lipids yields 9.3 kcal/g; oxidation of lean tissue yields 4.2 kcal/g.
3. Mean of 4.6 kcal/liter 02 consumed.

e Mean Vn /M for this size class was 35.2 M1 /g*h during the first 50 days of estivation, and 23.5
u2
M1 /g*h thereafter.
f
Mean V /M for sirenids in this class size was 17.4 pl/g*h during the first 60 days and 11.0 U1 /g*h
U2
thereafter.


32
than a 500 g estiva tor with lipid stores comprising only 3% of its dry
mass (the mean lipid content for summer animals). A very large $_.
lacertina with a large quantity of stored lipid, such as the 1125 g
female with 43% body lipid (Table 2-2), potentially could survive two
to three years without food. Even a 1 g si reid could survive for
several months (Table 2-2) on stored energy, and in most cases Florida
droughts last only a few weeks or months. Hence, during an average
drought, most of the sirenids in a population may be able to survive
by estivating. In a prolonged drought, however, the continuation of a
population of sirenids at a given site may be dependent upon the
survival of a few large individuals with greater than average lipid
stores.


CHAPTER III
WATER BALANCE DURING ESTIVATION
Introduction
When an amphibian remains inactive in a burrow energy stores
decline because energy cannot be replenished until the animal can
emerge and feed. Body water fluxes are more complex, because water
can be gained or lost at several sites (Fig. 3-1). In amphibians
water can be lost by evaporation from the respiratory surfaces, via
urine, or across the skin. Most vertebrates must eat or drink to
replenish body water, for their only source of water gain during
prolonged inactivity is the very slight amount of metabolic water that
is formed when foodstuffs are oxidized. Amphibians, on the other
hand, can take up water across their permeable skin (for review see
Duellman and Trueb 1986) and many can reabsorb water from their
urinary bladder (e.g., Ruibal 1962; Main and Bentley 1964; Bentley
1966). In addition, amphibians and lungfish that estivate burrow into
the soil to avoid desiccating surface conditions and employ various
strategies to maintain water balance.
One strategy involves increasing resistance to water loss as much
as possible by forming an impermeable "cocoon." In estivating African
lungfish (Protopterus) this cocoon is composed of dried mucus (Kitzan
and Sweeney 1963), but in most estivating amphibians studied thus far
electron microscopy has revealed the cocoon to be composed of multiple
33


FIG. 3-1. Pathways of water exchange in an estivating amphibian.


WATER GAIN
Metabolic Wafer
Soil Water
Bladder Water
WATER LOSS
-> Respiratory
> Soil
Co
cn
* Urine


36
layers of unshed epithelial cells (Lae and Mercer 1967; McClanahan et
al. 1976; Loveridge and Craye 1979; RuiDal and Hillman 1981). In two
anurans, Pyxicephalus adspersus (Loveridge and Withers 1980) and
Lepidobatrachus llanensis (McClanahan et al. 1976), the cocoon of
estivators reduces water loss so effectively that these animals can
survive for several months in dry soil with little change in
concentrations of their internal solutes.
A second strategy for water balance during estivation has been
described for spadefoot toads. These animals maintain a favorable
water potential gradient with moist soil such that water is absorbed
from the soil across the skin. Scaphiopus hammondii can decrease
their body water potential to levels as low as -15 bars and thus
absorb water from any soil with a higher water potential (Ruibal et
al. 1969). Spadefoot toads maintain these low water potentials
primarily by accumulating urea in their plasma, thereby greatly
increasing their osmotic potential without disrupting ion balance
(McClanahan 1967, 1972; Shoemaker etal. 1969).
The objectives of this portion of the study were to investigate
adaptations that allow S_. lacertina and P_. stria tus to survive the
dehydrating conditions of drought and to compare these adaptations to
those of other estivating amphibians. One specific area investigated
was the way in which these animals maintain water balance during
estivation, that is, whether they become water-resistant or exchange
water with the soil. The contribution of the urinary bladder to water
balance and the effect of estivation on plasma and urine solute


37
concentrations were determined. In addition, the effects of body size
and soil water potential on potential survival time were studied.
Materials and Methods
Siren lacertina and P_. stria tus were collected and induced to
estivate in the laboratory as previously described. These estivators
were maintained in moist soil (5 to 12% water content) so that plasma
parameters would reflect a hydrated state. Blood and urine samples
were collected from three S_. lacertina on day 210 of estivation and
from five S_. lacertina on day 260 of estivation. Concurrently, blood
samples were taken from 13 freshly caught, aquatic S_. lacertina. An
attempt was made to collect urine from the aquatic animals as well.
Animals were maintained at 23C for all experiments.
Animals were anesthetized with sodium brevitol (0.01 mg/g) and
blood was collected by cardiac puncture using a heparinized syringe
and a 23 gauge needle. Each blood sample was centrifuged, the
hematocrit determined and the plasma frozen for later analysis. Urine
was collected by palpating the area of the urinary bladder; these
samples were frozen immediately. To estimate the volume of urine held
in the bladder of each estiva tor, animals were weighed before and
after urine was expressed.
Plasma and urine samples later were thawed for the following
analyses. Sodium and potassium concentrations ([Na+], [K+]; meq/1)
were determined for 5 yl samples using an Instrumentation Laboratory
443 Flame Photometer. Urea and ammonia concentrations ([NH^], [NH*];
mmol/1) were determined using the colorimetric Berthelot method (Sigma


33
test kit 640). Chloride concentration ([Cl-]; meq/1) was determined
for 10 yl samples using a Radiometer CMT 10 Chloride Titrator. A
Wescor 5100 B Vapor Pressure Osmometer was used to determine the total
osmotic concentration (m0sm/kg) of 5 U1 samples. A one-tailed
Students t-test was used to compare sample means of estiva tors and
active animals for each parameter.
Rates of water loss and gain were measured for estivating S_.
lacertina (3-550 g body mass) and estivating P_. stria tus (less than
2 g) in soils of varying water content. The soil used for these
experiments was obtained from typical sirenid habitat in Alachua
County, Florida. Mechanical analysis of this soil established the
composition as 92.662 sand (primarily 0.25-0.50 mm particle size),
4.522 silt and 2.322 clay. This soil was mixed thoroughly and
filtered through a screen (1 mm mesh) to remove debris. A
characteristic moisture curve for this specific soil was constructed
by beginning with saturated soil and then measuring water potential
and water content at several intervals as the soil dried slowly in
room air. Water potential (- bars) was measured with a ceramic tip
tensiometer. Soil water content was determined by weighing the
sample, drying it to a constant mass and then reweighing it. The
percent of mass lost during drying represented the percent of water
content by mass. Once the characteristic moisture curve was
established the soil water potential of any sample of this soil could
be determined by calculating percent water content.
Large plastic containers (50 x 39 x 20 cm) were set up to hold
soils of three different moisture contents (0.72, 5.02 and 6.02


39
water). Air dry soil (0.7? water) was used to simulate the most
dehydrating possible field conditions. Preliminary observations
indicated that estiva tors maintained mass in soil with greater than
7.0? water content; therefore, slightly drier soils (5.0? and 6.0?
water content) were used to establish the point at which estiva tors
began to lose water to soil. Each container was tightly covered and
the water content of the soil was checked periodically to insure
stability. Salamanders estivating for seven months or more were used
for this experiment. Estiva tors had been maintained in moist soil
(10-12? water content) to insure maximum hydration before these
experiments. They were then exposed to the most dehydrating soil
(0.7? water content). After this they were exposed to the soils of
different water content in the following order: 5.0?, 0.7? and
6.0?. Each animal was weighed and then buried in the soil with only
its head exposed. Respiratory water loss was assumed minimal because
estiva tors ventilate only once or twice each hour. After two hours
the animal was excavated, any soil adhering was carefully brushed off,
and the animal was reweighed. All mass changes were recorded as water
lost or gained (mg/g body mass hour). Data from animals that moved
or urinated (as indicated by any moisture around the cloaca) during
the experiment were discarded. The protocol was designed to maximize
the rates of water exchange by putting hydrated salamanders into
dehydrating soil for measurements of water loss, then moving these
dehydrated animals into soil with a higher water potential to
determine rates of water uptake. For example, animals were placed in


40
tne driest soil (0.7% water) to dehydrate them prior to exposure to
the soil with 6% water content.
The tail tip of an estivating S_. lacertina (day 210) was removed
and examined to determine the structure of the cocoon. The tissue was
fixed in 10% neutral buffered formalin, transferred to 70% ethanol and
then prepared for paraffin embedding. The tissue was sectioned at
10 ym, stained with Alcian Blue and counter-stained with Hematoxylin
and Eosin (Humason 1972) for examination by 1ight microscopy. Because
Alcian Blue stains mucopolysaccharides, it was used to indicate
whether mucus was a major component of the cocoon. Hematoxylin stains
nuclear material; hence, it was used to determine the presence or
absence of cells in the cocoon layer.
Rasults
The body position of estivating sirenids is such that most of the
surface area of the animal is in direct contact with the surrounding
soil. Siren lacertina do not coil, but maintain a somewhat S-shaped
configuration. In some individuals the tail was curled forward with
the tip touching the body. Estivating P_. stria tus were usually curled
into a figure eight with the head resting near the tail.
Blood parameters of S_. lacertina estivating 210 days were not
significantly different from those of animals estivating 260 days;
therefore, these data were pooled for comparison with the aquatic
animals. Plasma ion concentrations ([Na+], [K+], [Cl-]) were not
significantly different between the two groups (Table 1). However,
plasma urea concentration was significantly higher in the estivators


TABLE 3-1
Solute Concentrations of Plasma from Active S. lacertina and of
Plasma and Urine from Estivating S. lacertTna (Mean S.E.)
Sodium
(meq/1)
Potassium
(meq/1)
Chloride
(meq/1)
Urea
(mmol/I)
Ammonia
(mmol/I)
Other'1
Total
(mOsm/kg)
Active Animals
PLASMA (n=13)
119.02.2
3.80.2
78.13.3
7.81.5
2.410.2
13.2
229.3111.7
Estivators
PLASMA (n=3)
113.04.5
3.80.4
71.94.6
49.115.0
4.210.9
22.2
264.219.3
Estiva tors
LJRIME (n=3)
11.3l6.7
8.911.8
6.012.5
63.617.4
45.7110.2
45.0
130.5125.3
a Other = plasma proteins, Ca++, Mg+, glucose, HCO3, etc. This component makes up the difference
between the total concentration and the summed concentrations of measured solutes.


42
(t = 9.39, p < .001) as was the total plasma osmotic concentration (t
= 3.89, p < .005). The mean hematocrit was higher in estivators (33.9
3.9%) than in active animals (26.1 2.7%), but the difference was
not statistically significant (t = 1.55, p > .05).
No urine could be expressed from any active Siren despite
numerous attempts. Estivating sirenids were never observed to void
urine unless disturbed by handling. Urine collected from 10
estivating S_. lacertina (mean mass of 479.7 41.2 g) made up 5.3
0.8% (mean S.E.) of the mass of these animals. The maximum amount
of stored urine measured was 10.1% of body mass. Urine collected from
estivators was hyposmotic in comparison to the plasma (Table 3-1).
Concentrations of Na+ and Cl" were significantly lower in urine than
in plasma (t = 18.4, p < .001; t = 2.21, p < 0.05), whereas the
concentration of K+ was slightly higher in urine (t = 2.53,
p < 0.025). Urea concentration was not significantly higher in the
urine (t = 1.51, p > 0.05). Levels of ammonia were very low in the
plasma of both aquatic (2.4 0.2 mmol/1) and estivating (4.2 0.9
mmol/1) S_. lacertina. Ammonia concentration in the urine of
estivators was ten times that in the plasma (45.7 10.2 mmol/1).
Soil water potential of the sand used in these experiments
remained high (between 0 and -1 bars) when soil water content was
greater than 8% (Fig. 3-2). At soil water contents below 6% the water
potential of this soil begins to increase exponentially with slight
decreases in water content. The rate of water exchange with the soil
was related to body size of the salamanders. This relationship was
strongest in the driest soil (Fig. 3-3), where it can be related as a


FIG. 3-2. Characteristic moisture curve for soil used in water
exchange experiments.


WATER POTENTIAL (-bars)
-P
-P*
ro "


FIG. 3-3. Rates of water loss for estivating S. lacertina in soil
with Q.7% water content (closed circles) and in soil with
5.0% water content (open circles).


46


47
power function (y = 215x-^*^, r^ = 0.96). Two 1 g P_. stria tus placed
in this same soil (0.7% water content) lost water at rates of 51 and
92 mg/g'h. Six of 14 animals maintained their original mass in the
soil with 5.0% water content; the other eight lost mass, but at a much
lower rate than in the drier soil (Fig. 3-3). Similarly, 4 of 13 S_.
lacertina maintained their weight in the soil with 6.0% water content,
and the remainder gained water from this soil (Fig. 3-4). Thus, a
positive water balance is achieved by estiva tors in soil with water
potential greater than -5 bars (6% water content), whereas estivators
in drier soil (i.e., 5% 1^0 content, less than -5 bars) may lose water
(Fig. 3-4).
Light microscopy revealed the dry outer layer or "cocoon" of
estivating S_. lacertina to be composed primarily of dead, squamous
epithelial cells. This layer did not stain for mucopolysaccharides as
it would if mucus were the primary component, but remained brown in
color. In a few animals that were allowed to dehydrate in dry soil,
the cocoon appeared to be thicker than in hydrated estivators.
Discussion
The long cylindrical body shape of sirenid salamanders results in
a relatively high surface to volume ratio. While this may be
advantageous for cutaneous respiration in water, it is disadvantageous
during a drought because it creates a large surface area for water
loss. Siren lacertina are fairly stout animals with a thick, muscular
body wall and tightly wrapped skin, and they are incapable of coiling
up to reduce surface area. Pseudobranchus striatus are more slender


FIG. 3-4. Rates of water exchange with the soil for estivating S_.
lacertina in soil with 5.0% water content (closed circles)
and in soil with 6.0% water content (open circles).


100 200 300 400 500 600
MASS (g)
CHANGE IN MASS (mg/g-h)
i i i i i i
OJOl -I^GOlO-tO-tlOCO


50
and can coil somewhat, but most of the surface area of both species is
in direct contact with soil during estivation. Consequently, water
exchange with the soil is the most important factor in water balance
of estivating sirenids. The rate of water exchange with soil is a
function of several parameters, primarily surface area, resistance and
the difference between the water potential of the soil and that of the
animal.
The water potential of an estivating animal is related to the
osmotic potential of its body fluids. An amphibian with high plasma
solute concentrations has lower water potential (- bars) than an
animal with lower plasma solute concentrations, and all else being
equal more water will move across the skin of the first animal. The
water potential of estivating S_. lacertina is increased by urea
accumulated in the plasma. Elevated plasma urea levels in estiva tors
accounted for the difference between total plasma osmolality of
estiva tors and aquatic animals. On the other hand, plasma ion
concentrations appear to be closely regulated. This strategy of
decreasing water potential by storing urea has been demonstrated in
several species of amphibians, including Ambystoma tigrinum (Delson
and Whitford 1973), Xenopus laevis (Balinsky et al. 1967), Bufo
viridis (Oegani et al. 1984), and several species of Scaphipus
(McClanahan 1967; Shoemaker et al. 1969; Jones 1980). In these
species plasma ion concentrations increased much less (no more than
two times hydrated levels) than plasma urea levels (up to 30-fold
increase). The difference between the two variables of soil water
potential and water potential of the animal not only determines the


51
direction of water exchange (water moves from an area of higher to
lower water potential), but the rate at which the exchange occurs.
Sirenids lost water in soil with water potentials lower than -5 bars
(5.0% water content), but they lost water more rapidly in the soil
with 0.7% water content (water potential less than -15 bars). The
rate of water loss was greatly affected by the third variable, surface
area of the estivator. Small S_. lacertina and P_. stria tus dehydrated
rapidly due to their high surface to volume ratio. The relationship
of body size to rate of water exchange could be seen most clearly in
the driest soil (0.7% water), where hydric properties of the soil play
the major role in determining water loss. In soils with 5.0 or 6.0%
water content the correlation between rate of water exchange and body
size is less evident. This increased variability in rates indicates
that water exchange in soils of higher water potential may be mediated
more by hydric properties of the animal than by those of the soil.
Variability in rates of water exchange may reflect differences in
water potential of individual animals and/or differences in resistance
to water flux.
Resistance is the fourth variable in determining rates of water
exchange and is the most difficult to measure. Resistance as defined
here is the capacity of the outer layer of the animal to retard water
flux. This involves many factors such as the degree of vasodilation
or vasoconstriction, hormonally mediated processes and physical
properties of the outer layer. A salient characteristic of estivating
amphibians is the outer covering of the animal referred to as the
cocoon, and this is usually the focus of any investigation of


52
resistance to water loss. The cocoon of sirenids examined in this
study appears to be layers of stratum corneum. Examination by light
microscopy revealed flattened, nucleated cells. Furthermore, these
layers do not stain for mucopolysaccharides as they would if mucus
were the main component. These findings differ from those of Reno st
al. (1972) who described the cocoon of estivating intermedia as
layers of dried mucus with no cellular integrity. For sirenids in
this study, the cocoon layer could be peeled off in sheets and
preserved intact, indicating that it is much like a typical sned skin
of any amphibian. McClanahan et al. (1983) described cocoon formation
in Lepidobatrachus llanensis as a normal shedding cycle in which the
layers do not detach from the animals. Water loss in air in cocooned
L_. Ilamensis was reduced as much as 70% after one week of estivation
(McClanahan et al. 1976) and was further reduced with each additional
layer of stratum corneum added to the cocoon of these frogs during
estivation (McClanahan etal. 1983). Unfortunately, the degree to
which the cocoon retards water flux in soil has not been measured for
any estiva tor. These types of measurements are difficult to make, and
there is the further complication of trying to separate the
contribution of the cocoon from the other factors involved in
resistance. Using an in vitro technique, Reno et al. (1972) measured
the effect of the cocoon of S_. intermedia upon water uptake from agar
blocks and found that the cocoon alone decreased water uptake by
31%. Dehydrated Siren did appear to have a thicker cocoon layer than
hydrated estivators, and it may be that resistance is varied by
increasing the rate of shedding; however, this warrants further study.


53
Amphibians from different environments may respond differently to
drought depending upon the type of soil in which they burrow. The
strategy employed by sirenids, spadefoot toads and others of storing
urea and absorbing water from the soil may be useful only in sandy
soils, where large interstitial spaces cause high water potentials
even at low moisture contents. Frogs that become almost waterproof,
such as P_. adspersus and l_. llanensis, may live where soils have a
high clay content. Clay soils have small pore size and consequently
low water potential even at high moisture content (Noble 1974). Thus
amphibians burrowed in this type of soil may not be able to reduce
their water potential below that of the soil; they therefore avoid
dehydration by becoming as impermeable to water loss as possible. The
possibility that amphibians can vary resistance according to the water
potential of the soil in which they burrow warrants additional study.
Several estivating amphibians store large quantities of dilute
urine when in positive water balance and later reabsorb water from the
bladder to rehydrate body fluids during drought (e.g., Ruibal 1962;
Bentley 1966). In some fossorial desert frogs, bladder volumes may
account for as much as 50% of the animals' body mass (Bentley 1966).
Siren lacertina can reabsorb water from its bladder (Bentley 1973).
No urine could be collected from aquatic animals, possibly because
active sirenids excrete urine continuously. Urine expressed from
hydrated estiva tors averaged 5.3% of body mass, and a maximum of 10.0%
of body mass was measured for one animal. These values are lower than
those reported for most other estivating amphibians, but are higher
than the values of 1 and 2% reported for the aquatic amphibians


55
would be due to metabolized tissue, and sirenids could survive as long
as energy stores persisted. Under field conditions it may be rare for
water to be the limiting factor in survival during estivation. In
Florida brief showers occur even during severe droughts, and although
these showers do not reflood the habitat, they may suffice to moisten
the soil such that sirenids can maintain a positive water balance.
Furthermore, water potential can vary greatly from site to site
depending upon such factors as soil type, plant cover and proximity to
the water table. For example, sandy soil within a meter of the water
table would remain virtually saturated due to capillary action, even
during a drought. Sirenids in such a place would not be in danger of
dehydration and could serve to re-establish populations at sites that
did reach critical water tensions during drought.


CHAPTER IV
SUMMARY AND CONCLUSIONS
Throughout the southeastern coastal plain of the United States
there is an abundance of shallow water habitat suitable for sirenid
salamanders. This is often a transient resource, however, because
drought is common in this region. Sirenid salamanders, although
aquatic, are well-adapted for survival during drought and thus can
exploit impermanent bodies of water. As their habitat dries out,
sirenid salamanders burrow into the substratum and remain inactive
until the area is reflooded. Survival during estivation is due to
their abilities to live for prolonged periods on stored energy and to
maintain water balance in drying soil.
Energy is unlikely to be the limiting factor in sirenid survival
during estivation except in rare cases. The metabolic rates of
estivating S_. lacertina and P. stria tus are reduced 60 to 70S below
rates of resting aquatic sirenids. Coupled with substantial energy
stores, these low rates of energy consumption would permit large S_.
lacertina to survive for two to three years without food and would
allow even a 1 g animal to survive for several months. In a prolonged
drought the largest animals with the greatest energy stores may be the
only survivors, but these could serve to found a new population.
Water is more likely to be limiting to survival than energy, but
under usual field conditions lethal dehydration of estivating sirenids
55


57
is probably rare. The cocoon of lacertina, composed of dead
epithelial cells, may retard water exchange (Reno et al. 1972), but it
does not make estiva tors impermeable to water loss. Si reid
salamanders exchange water with soil at a rate that shows a strong
inverse correlation with body size, indicating that relative surface
area is a major factor in water balance. The other major determinant
of the rate and direction of water flux is the magnitude of the
difference in water potential of the soil and water potential of the
esti va tor.
Water potential of an animal buried in soil is dependent
primarily upon the concentration of internal solutes in the animal's
body fluids. Siren lacer tina that had been estivating seven or more
months had a mean plasma osmotic concentration of 264.2 9.8 mOsm/kg,
which is the equivalent of -5.8 bars of water potential. Most animals
maintained a positive water balance in soil with water potential
greater than -5.7 bars, but began to lose water in soil with water
potential lower than this. Aquatic S_. lacertina had a lower mean
plasma osmotic concentration (229.8 11.7 mOsm/kg), the equivalent of
-5.0 bars of water potential, and would lose water in soil with a
higher content than would estivators. This difference in osmotic
concentration is due to the higher plasma urea concentration of the
estivating S_. lacerti na. The salamanders used in this experiment had
been kept in moist soil and were hydrated; it is possible that plasma
urea concentrations can be increased in estivators as they become
dehydrated, decreasing their water potential even further. This has
been well-documented in species such as Scaphiopus couchii


58
(McCl ana han 1972), which can actively increase urea concentrations in
body fluids in response to decreasing soil water potential.
Water potential of soil is dependent upon the soil structure and
composition (i.e., percentages of sand, silt and clay) and upon the
water content (Fig. 4-1). Clay has smaller pore sizes than sand,
higher matric potentials, and consequently, much higher water
potential than sand at any given water content. Thus, a siren
estivating in clay would be in a potentially more stressful hydric
environment than one in sand. It may be that sirenid salamanders can
inhabit drought-prone waters only in areas of sandy soil. This could
help to explain the geographic distribution of sirenids, which live
primarily in the coastal plain, where soils tend to be sandy. Even
within a large area such as the coastal plain soil type varies, and
there may be areas within this mosaic that are unsuitable for sirenid
estivation. Hence, sirenid distribution may be affected by soil type
as well as water availability.
Although the physiological mechanisms associated with estivation
seem to be evolutionarily conservative among amphibians, many of these
adaptations are not present in other vertebrates. Indeed, in many
ways amphibians such as sirenid salamanders are uniquely suited to
survival during drought. Rates of energy consumption are low in
amphibians, particularly salamanders, even in comparison to reptiles
(Pough 1983). Other vertebrates must rehydrate by drinking or eating;
amphibians can absorb water from moist soil and store excess water in
the bladder for later use. Lastly, the ability to tolerate high
concentrations of urea in body tissues has not been demonstrated for


FIG. 4-1. Hypothetical water potentials of different soil types at
varying water content. (See Noble 1974 for a review of
soil water potentials.)


60


61
any of the higher vertebrates. Ironically, the highly permeable skin
of amphibians, which would appear to be a disadvantage in xeric
conditions, is actually highly advantageous (e.g., Bentley 1966;
McClanahan 1972). Even though amphibians cannot maintain prolonged
surface activity during drought, they can survive for months or years
in the absence of food and free water, a feat well beyond the
abilities of any endotherm. In the case of sirenid salamanders, the
ability to survive drought by estivating allows them to exploit
potentially transient aquatic habitats that would be uninhabitable for
many species.


LITERATURE CITED
Balinsky, J.B., E.L. Choritz, C.G.L. Coe, and G.S. Van Der Schans.
1967. Amino acid metabolism and urea synthesis in naturally
aestivating Xenopus laevis. Comp. Biochem. Physiol. 22:59-63.
Belkin, D.A. 1965. Reduction of metabolic rate in response to
starvation in the turtle Sternothaerus minor. Copeta 1965:367-
363.
Benedict, F.G. 1932. The physiology of large reptiles. Carnegie
Inst. Washington Publ. 425.
Bentley, P.J. 1966. The physiology of the urinary bladder of
amphibia. Biol. Rev. 41:275-316.
Bentley, P.J. 1973. Osmoregulation in the aquatic urodeles Amphiuma
means (the congo eel) and Siren lacertina (the mud eel). Effects
of vasotocin. Gen. and Comp. Endocrinology 20:386-391.
Bentley, P.J., and H. Heller. 1964. The action of neurohypophysical
hormones on the water and sodium metabolism of urodele
amphibians. J. Physiol. 171:434-453.
Bentley, P.J., A.K. Lee, and A.R. Main. 1958. Comparison of
dehydration and hydration of two genera of frogs (Heleioporus and
Neobatrachus) that live in areas of varying aridity. J. Exp.
Zool. 35:577-684.
Brenner, F.J. 1969. The role of temperature and fat deposition in
hibernation and reproduction in two species of frogs.
Herpetologica 25:105-113.
Burch, P.R., and J.T. Wood. 1955. The salamander Siren lacertina
feeding on clams and snails. Copeia 1955:255-256.
Byrne, J.J., and R.J. White. 1975. Cyclic changes in liver and
muscle glycogen tissue lipid and blood glucose in a naturally
occurring population of Rana catesbeiana. Comp. Biochem.
Physiol. 50A:709-715.
Cockrum, L. 1941. Notes Siren intermedia. Copeia 1941:265.
Conant, R. 1975. A field guide to reptiles and amphibians of eastern
and central North America. Houghton Mifflin Co., Boston.
62


64
Hudson, J.W., and G.A. Bartholomew. 1964. Terrestrial animals in dry
heat: Aestivators. Pages 541-550 in D.B. Dill, E.F. Adolph and
C.G. Wilbur, eds. Handbook of physiology. Williams and Wilkins
Co., Baltimore.
Humason, G.L. 1972. Animal tissue techniques. W.H. Freeman and Co.,
San Francisco.
Jones, R.M. 1980. Metabolic consequences of accelerated urea
synthesis during seasonal dormancy of spadefoot toads, Scaphiopus
couchi and Scaphiopus multipiicatus. J. Exp. Zool. 212:255-257.
Kitzan, S.M., and P.R. Sweeny. 1963. A light and electron microscope
study of the structure of Protopterus annectens epidermis. I.
Mucous production. Caad. J. Zool. 46:767-773.
Lee, A.K., and E.H. Mercer. 1967. Cocoon surrounding desert-dwelling
frogs. Science 157:87-83.
Loveridge, J.P., and G. Craye. 1979. Cocoon formation in two species
of Southern African frogs. South Africa J. Sci. 75:13-20.
Loveridge, J.P., and P.C. Withers. 1981. Metabolism and water
balance of active and cocooned African bull frogs Pyxicephalus
adspersus. Physiol. Zool. 54:203-214.
Main, A.R., and P.J. 3entley. 1964. Water relations of Australian
burrowing frogs and tree frogs. Ecology 45:379-332.
Martof, B.S. 1969. Prolonged inanition in Siren lacertina. Copeia
1969:285-239.
McClanahan, L. 1967. Adaptations of the spadefoot toad, Scaphiopus
couchi, to desert environments. Comp. Biochem. Physiol. 20:73-
99.
McClanahan, L., Jr. 1972. Changes in body fluids of burrowed
spadefoot toads as a function of soil water potential. Copeia
1972:209-216.
McClanahan, L., R. Ruibal, and V.H. Shoemaker. 1983. Rate of cocoon
formation and its physiological correlates in a ceratophryd
frog. Physiol. Zool. 56:430-435.
McClanahan, L.L., Jr., V.H. Shoemaker, and R. Ruibal. 1976.
Structure and function of the cocoon of a ceratophryd frog.
Copeia 1976:179-185.
Morton, M.L. 1981. Seasonal changes in total body lipid and liver
weight in the Yoseinite toad. Copeia 1931:234-238.


55
Noble, P.S. 1974. Introduction to biophysical plant physiology.
W.H. Freeman, San Francisco.
Pough, F.H. 1983. Amphibians and reptiles as low-energy systems.
Pages 141-188 _m_ W.P. Aspey and S.I. Lustick, eds. Behavioral
energetics. Ohio State University Press, Columbus, Ohio.
Ray, C. 1958. Vital limits of desiccation in salamanders. Ecology
39:75-83.
Reno, H.W., F.R. Gehlbach, and R.A. Turner. 1972. Skin and
aestivational cocoon of the aquatic amphibian, Siren
intermedia. Copeia 1972:625-631.
Rose, F.L. 1967. Seasonal changes in lipid levels of the salamander
Amphiuma means. Copeia 1967:562-566.
Ruibal, R. 1962. The adaptive value of bladder water in the toad,
Bufo cognatus. Physiol. Zool. 35:213-223.
Ruibal, R., and S.S. Hillman. 1981. Cocoon structure and function in
the burrowing hylid frog, Pternohyla fodiens. J. Herpetology
15:403-408.
Ruibal, R., L. Tevis, Jr., and V. Roig. 1969. The terrestrial
ecology of the spadefoot toad Scaphiopus hammondii. Copeia
1969:571-584.
Seymour, R.S. 1973a. Energy metabolism of dormant spadefoot toads
(Scaphiopus). Copeia 1973:435-446.
Seymour, R.S. 1973b. Gas exchange in spadefoot toads beneath the
ground. Copeia 1973:452-460.
Seymour, R.S. 1973c. Physiological correlates of forced activity and
burrowing in the spadefoot toad, Scaphiopus hammondii. Copeia
1973:103-115.
Shoemaker, V.H., l.L. McClanahan, Or., and R. Ruibal. 1969. Seasonal
changes in body fluids in a field population of spadefoot
toads. Copeia 1969:585-591.
Ultsch, G.R. 1973. Observations on the life history of Siren
lacertina. Herpetologica 29:304-305.
Ultsch, G.R. 1976a. Ecophysiological studies of some metabolic and
respiratory adaptations of sirenid salamanders. Pages 287-312 i^
G.M. Hughes, ed. Respiration of amphibious vertebrates.
Academic Press, London.


56
Ultsch, G.R. 1976b. Respiratory surface area as a factor controlling
the standard rate of Op consumption of aquatic salamanders.
Resp. Physiol. 26:357-369.
van Beurden, E.K. 1980. Energy metabolism of dormant Australian
water-holding frogs (Cyclorana platycephalus). Copeia 1980:787-
799.
Wakeman, J.R, and G.R. Ultsch. 1975. The effects of dissolved Op and
COo on metabolism and gas-exchange partitioning in aquatic
salamanders. Physiol. Zool. 48:348-359.
Withers, P.C. 1977. Measurement of V
J2
water loss with a flow through mask.
123.
J.
, and evaporative
1. Physiol. 42:120-


BIOGRAPHICAL SKETCH
Kay Etheridge was born in Clarksdale, Mississippi, in 1954. She
grew up in Alabama and attended Auburn University where she received
her B.S. in zoology in 1975 and her M.S. in zoology in 1980. Hot yet
satiated with higher education, she migrated still farther south to
the University of Florida where she pursued her Ph.O. During this
pursuit she also worked with manatees and became interested in
tropical biology during a course in Costa Rica. Her primary research
interests involve the physiological ecology of reptiles and
amphibians. Her spare time is devoted largely to the practice of
martial arts and the search for the ultimate chocolate ice cream.
67


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
^77 <
, .
Martha L. Crump, Chairman
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
(aJ
Walter Judd ?
Associate Professor of Botany
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
if
! M L ,
Harvey B. Lilflywhite
Professor of oology


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Michelle Wheatly
Assistant Professor of Zoology
This dissertation was submitted to the Graduate Faculty of the
Department of Zoology in the College of Liberal Arts and Sciences and
to the Graduate School and was accepted as partial fulfillment of the
requirements for the degree of Doctor of Philosophy.
December, 1986
Dean, Graduate School


Full Text
UNIVERSITY OF FLORIDA
3 1262 08554 1448


ESTIVATION IN THE SIRENID SALAMANDERS,
SIREN LACERTINA (LINNAEUS) AND
PSEUDÓBRANCHU'S'STRIATüS (LE CONTE)
BY
KAY ETHERIDGE
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1986

ACKNOWLEDGMENTS
I would like to thank several people for their invaluable
assistance during this study. Marty Crump, my major advisor, has been
a great help throughout my studies, and her encouragement and common
sense advice have helped me over many obstacles. John Anderson, David
Evans, Harvey Lillywhite, Frank Nordlie and Michele Wheatly not only
gave me guidance and technical assistance, but also trusted me with
their equipment. Archie Carr and Walter Judd have advised me during
this study and have reviewed this dissertation. Mark Seyfried helped
me comprehend soil physics, and Lou Guillette introduced me to the art
of histology. Chip Oglesby, Allison Rogers and Sam Ward, who
volunteered their time through the undergraduate research assistant
program, were a tremendous help during one of the most labor intensive
portions of this study. Don Banknight helped supply many of the
salamanders used in this study.
I am grateful to many of the faculty, staff and graduate students
of the Department of Zoology for their assistance in innumerable
facets of this study. Financial support for this work was from the
Department of Zoology and a Sigma Xi Grant-in-Aid of Research.
Finally, I wish to thank my family and friends for their support
during my studies.
ii

TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
ABSTRACT iv
CHAPTERS
I INTRODUCTION 1
Background 1
Study Animals and Habitat 3
Objectives 5
II THE ENERGETICS OF ESTIVATION 9
Introduction 9
Materials and Methods 10
Resul ts 13
Discussion 23
III WATER BALANCE DURING ESTIVATION 33
Introduction 33
Materials and Methods 37
Resul ts 40
Discussion 47
IV SUMMARY AND CONCLUSIONS 56
LITERATURE CITED 62
BIOGRAPHICAL SKETCH , 67
i i i

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
ESTIVATION IN THE SIRENID SALAMANDERS,
SIREN LACERTINA (LINNAEUS) AND
PSEUDOBRANCHUS SÍRIATUS (LE CONTE)
BY
KAY ETHERIDGE
December, 1986
Chairman: Martha L. Crump
Major Department: Zoology
Siren lacertina and Pseudobranchus stria tus are aquatic
salamanders that inhabit drought-prone waters in the southeastern
United States. When drought occurs, sirenids burrow into the
substratum and remain inactive until the habitat is reflooded. This
study investigated adaptations that allow these two species to survive
drought.
Siren lacertina and P. stria tus were induced to estivate in the
laboratory and several parameters were measured: rates of metabolism,
blood lactate levels, ventilation rates, rates of water exchange with
soil, urinary bladder volumes and solute concentrations of plasma and
urine. In addition, lipids stores were measured in animals from
aquatic populations, and the cocoon of an estivating S_. lacertina was
examined by light microscopy.
In both species resting metabolic rates are 60 to 70% lower in
estiva tors than in aquatic animals. At these low metabolic rates
iv

adult S. lacertina can survive two to three years without food.
Smaller lacertina and P_. stria tus have higher mass-specific
metabolic rates during estivation, but even a 1 g sirenid can survive
for several months on stored energy. Ventilation rates decrease
during estivation, but low blood lactate levels indicate that
respiration is aerobic.
The cocoon is composed of dead squamous epithelial cells. This
layer does not block water movement and estivating sirenids exchange
water with the soil. The rate of water exchange with the soil
increases with a decrease in body size. Rate and direction of water
exchange are also related to the water potential of the soil.
Estiva tors maintain a positive water balance in soil with water
potential greater than -5 bars, but begin to lose water in drier soil.
Siren lacertina store dilute urine in their bladder; the mass of
this urine may be the equivalent of as much as 10% of their body
mass. Plasma concentrations of sodium, potassium and chloride are
similar in aquatic animals and estivators; however, plasma urea
concentrations are six times higher in estivators. Due to urea
accumulation, plasma osmolality is higher in estivators than aquatic
animals. This lowers the water potential of estivators and decreases
the rate at which they will lose water in very dry soil.
v

CHAPTER I
INTRODUCTION
Amphibians and reptiles can be described as low energy systems in
comparison to birds and mammals, which could be called high energy
systems (Pough 1983). This comparison relates to the fact that lower
vertebrates are primarily ectothermic and expend little energy for
maintenance of body temperature. Therefore, reptiles and amphibians
have low rates of energy intake and expenditure relative to birds and
mammals, which fuel their high metabolic rates with high rates of
energy intake. Differences in rates of energy flow have several
consequences, one of which is the frequency at which an animal must
"refuel." High energy systems require a constant source of food; low
energy systems can rely on a more variable supply. Under adverse
conditions most ectotherms can reduce their energy costs and remain
inactive for prolonged periods until conditions improve. Some birds
and mammals can lower their energy demand for short periods (torpor)
or seasonally (hibernation), but they cannot begin to approach the
length of time that ectotherms can remain inactive. The ability of
ectotherms to remain dormant for long periods allows them
opportunities to exploit transient or ephemeral resources that would
not support a high energy endotherm.
Energy may not be the only limiting resource, however, and lack
of water can restrict the use of some environments. Of all the
1

2
tetrapod vertebrates, amphibians appear to be the most closely tied to
moist or aquatic habitats. Most amphibians have an aquatic larval
stage and skin that offers little resistance to water loss; hence,
they seem to be ill-adapted for survival in a dry environment.
Nevertheless, several species of anurans and a few salamanders do live
in xeric habitats; some examples are Amby stoma ti grin urn (Del son and
Whitford 1973), Scaphiopus multipiicatus and S. couchii (Ruibal et al.
1969), Heleioporus eyreia (Bentley et al. 1958), Limnodynastes
spenceri, Neobatrachus pictus and several species of Cyclorana (Lee
and Mercer 1967). Typically, these animals are terrestrial, nocturnal
species that spend most of their adult lives in underground burrows,
surfacing to feed and breed for relatively brief periods when water is
available. In addition to behavioral adaptations these amphibians
have in common several physiological adaptations that permit this type
of life history. As is the case with other ectotherms, their
metabolic costs are low, and they can survive long periods of
estivation on stored energy (e.g., van Beurden 1980). This type of
strategy has been most thoroughly studied for several species of
Scaphiopus, the spadefoot toads (Ruibal et al. 1969; Seymour 1973c;
McClanahan et al. 1976). Most studies of amphibian estivation have
focused on terrestrial or semi-aquatic anurans. However, one aquatic
anuran, Xenopus laevis (Balinsky et al. 1967), and one family of
aquatic salamanders, the Sirenidae, are known to estivate when their
habitats dry up. Little is known concerning the effects of drought
upon aquatic amphibians. This study focused on the adaptations that
enable sirenid salamanders to survive prolonged drought.

3
Study Animals and Habitat
All three species in the family Sirenidae are indigenous to
shallow water habitats in the southeastern United States. The two
species investigated in this study were the greater siren, Siren
lacertina Linnaeus, which ranges from the District of Columbia south
to the tip of Florida, and the dwarf siren, Pseudobranchus striatus Le
Conte, which is found from southern South Carolina to the eastern half
of the Florida panhandle, and south to the tip of Florida (Conant
1975). The third species in the family, which is not included in this
study, is the lesser siren, S_. intermedia Le Conte. These species are
similar in habitat and morphology, but are dissimilar in size; P_.
striatus rarely exceeds 25 cm in length, whereas lacertina may
reach almost 1 m.
Little is known about the life history of these secretive,
nocturnal salamanders. Reproduction occurs in late winter or early
spring and females deposit eggs singly or in pairs on submerged
aquatic vegetation (Goin 1941; Davis and Knapp 1953; U1tsch 1973).
Siren ingest large amounts of plant material along with prey items
such as crustaceans, mollusks and insect larvae, but it is not known
whether or not Siren digest cellulose (Davis and Knapp 1953; Burch and
Wood 1955; U1 tsch 1973; Hanlin 1978). Plant material has not been
reported in the gut of P_. striatus, but dwarf sirens do eat small
crustaceans and insect larvae (Freeman 1967). Sirenids may be among
some of the most productive salamanders; Gehlbach and Kennedy (1978)

4
found that S. intermedia was the dominant vertebrate species in a
Texas beaver pond, due in part to its great fecundity (151-226
eggs/female'year) and rapid growth to sexual maturity in one year.
This study was conducted from 1981 through 1986 in the vicinity
of Gainesville, Florida, where all three species occur sympatrically
in an array of aquatic habitats that vary in degree of permanency.
For example, all three species have been found both in the River Styx,
a permanent body of water, and in drought-prone ponds on Paynes
Prairie, Alachua County, Florida (A. Carr, pers. comm.). Typical
sirenid habitat in this area is characterized by shallow, soft-bottom,
weed-choked waters. One of the most common aquatic plants is the
introduced water hyacinth, Eichhornia crassipes, and sirenids are
often found in close association with the root systems of these
abundant floating plants. This type of habitat is uninhabitable for
many aquatic vertebrates because weed-choked waters are usually
hypoxic and hypercapnic (Ultsch 1976a), and are often transient
resources. Shallow aquatic habitats periodically dry out or change
with succession to a terrestrial environment, and survival of the
inhabitants is dependent upon an ability to withstand dehydrating
conditions, or an ability to move to new suitable habitat.
No evidence has been reported to suggest that sirenids migrate
overland in times of drought to seek new aquatic habitats. Instead,
they estivate during dry conditions by burrowing into the soil and
remaining inactive until the habitat is reflooded (Cockrum 1941;
Freeman 1958; Reno et al. 1972; Gehlbach et al. 1973). In the area of

5
this study drought can occur at any time of the year. Over a 70 year
period the summer months had the highest mean rainfall; however, in
1983 and 1984 there were summer droughts (Fig. 1-1). During this
study drought also occurred in winter and spring. Although the term
estivation was originally defined as summer inactivity (from the Latin
for summer, aestas), it also has traditional associations with
inactivity due to drought and is used in that sense here. Although
the ability to estivate permits these aquatic salamanders to colonize
potentially transient bodies of water, little is known about the
physiological mechanisms involved in estivation.
Objectives
This study centers on two species of sirenid salamanders (Siren
lacertina and Pseudobranchus stria tus) that serve as excellent models
for the study of estivation in amphibians; both species are aquatic,
but live in habitats susceptible to drought. Aquatic amphibians are
subjected to several stresses as their habitats dry up, including
dehydration, starvation and the accumulation of nitrogenous wastes
that are normally excreted in water. The objectives of this research
were to examine the adaptations used by sirenids to cope with these
stresses and to compare the abilities of these two species to survive
drought. These comparisons are important primarily because of the
size differences between these two species. Individuals of both
species were induced to estivate in the laboratory and, using a range
of sizes within each species, two major areas were investigated.

FIG. 1-1. Average monthly rainfall (cm) in the Gainesville, Florida, area, based on data from the
Agronomy Department, University of Florida, Gainesville, Florida. The solid bars
indicate the 70 year average, the striped bars indicate data from 1983, and the open
bars indicate data from 1984.

28
26
24
22
20
1 8
16
14
12
10
8
6
4
2
MONTH

8
Energetic Costs of Estivation
By measuring oxygen consumption during estivation, energy
expenditure was calculated and then compared to rates of energy
consumption in nonestivators. In addition, seasonal fluctuations in
energy stores available for use during estivation were measured by
extracting lipids from animals collected bimonthly throughout the
year.
Water Balance During Estivation
Rates of water loss and gain in soil were measured to determine
the effect of body size and soil water content on these rates. Plasma
and urine samples were analyzed to examine the effects of estivation
on ion concentrations and nitrogenous wastes.
Data from this study were used to determine adaptations used by
sirenids to survive drought and also allowed estimation of the length
of time different size classes can survive without standing water.
Finally, the responses of these aquatic animals to drought were
compared to those of terrestrial amphibians that estivate.

CHAPTER II
THE ENERGETICS OF ESTIVATION
Introduction
Because estivating animals are inactive and do not feed, they
must rely on stored energy for an unpredictable amount of time.
Potential survival time is dependent in part upon the quantity of
stored energy available to the estiva tor at the onset of estivation
and the rate at which this store is depleted. In amphibians, as in
most animals, energy stored as lipid tends to vary with body size, sex
and time of year (Rose 1967; Brenner 1969, Byrne and White 1975;
Fitzpatrick 1976; Morton 1981). Resting metabolic rates in amphibians
also vary with several factors, particularly temperature and body
size. Furthermore, in estivating lungfish (Delaney et al. 1974) and
anurans (Seymour 1973c; Loveridge and Withers 1981; van Beurden 1980;
McClanahan et al. 1983) resting metabolic rates are 50-70$ lower than
rates of nonestivators at the same temperatures.
In this part of the study the energetics of sirenid estivation
were investigated. Lipid content was measured in adult Siren
lacertina throughout a year to determine whether fat stores vary
seasonally, for if they do the timing of drought could affect survival
time. Metabolic rates were measured to estimate the potential amount
of time sirenids could survive before depleting stored energy and to
determine if metabolic rates could be reduced below resting levels.
9

10
In addition, the effect of body size on potential survival time was
studied by comparing the metabolic rates of adult and juvenile _S.
lacertina and Pseudobranchus striatus over a range of body sizes.
Materials and Methods
Metabolic Rates
Siren lacertina and Pseudobranchus striatus were collected from
ponds, rivers and lakes around Gainesville, Florida. Large S_.
lacertina were caught in a dipnet or on a hook and line using beef
heart as bait. Smaller animals were caught using a hand-held
dredge. Animals that were used for measurements of oxygen consumption
were held in water-filled aquaria for two weeks before estivation was
induced and were not fed during this period or during the experiment.
Both lacertina and P_. striatus were induced to estivate in the
laboratory at various times throughout the year. Animals were weighed
and placed individually into containers that held soil saturated with
water. Container size and soil depth varied with animal size;
containers were large enough to allow the salamanders to extend to
their full length, and soil depth was approximately four times the
body diameter of the animal. After animals burrowed into the soil,
the soil was allowed to dry slowly. Water was added as necessary to
maintain soil water content between 6 and 12% by mass. Estivating
animals were kept at 23°C, the mean annual soil temperature at 10 cm
depth in the area of Gainesville, Florida (based on data from the
University of Florida Agronomy Department).

11
Rates of oxygen consumption (V, ) were measured at one- to two-
u2
week intervals early in estivation and at one-month intervals after 50
days in estivation. For each point during estivation, sirenids
representing a range of body size were carefully excavated from their
burrows and weighed. Metabolic measurements were made for 53
individuals, ranging in mass from 0.9 g to 1061 g. Oxygen consumption
of animals smaller than 20 g was measured using a Gilson respirometer
and standard stoichiometric techniques. Oxygen consumption of larger
animals was measured using a flow-through system. Each animal was
placed in a plastic tube slightly larger than its body dimensions.
This tube was sealed except for incurrent and excurrent air ports at
opposite ends. A pump was used to draw air sequentially through the
tube, a column of soda lime to remove CO2, a column of silica gel to
remove water and an Applied Electrochemistry Oxygen Analyser Model
S-3A, to measure the fraction of oxygen in the air sample. Rates of
oxygen consumption were calculated using equations given by Withers
(1977) and were corrected to standard temperature and pressure
(STPO). All measurements were made during the animals' inactivity
periods, between 0800 and 1300 h. Handling of animals in an
estivating state had negligible effect. After the animal had spent
one to two hours in the metabolic chamber the rate of oxygen
consumption was stable enough to be measured. Rates of oxygen
consumption were measured at 23°C for all estivating sirenids. To
estimate for estiva tors, rates of oxygen consumption were measured
at 23°C and 32°C for seven S. lacertina (404 to 733 g) that had been
in estivation for more than four months.

12
Blood lactate levels were measured for estivating S_. lacertina to
determine if anaerobic metabolism was an important component of the
energy budget of these animals. Eight adult salamanders that had been
estivating for seven or more months were excavated and anesthetized
with sodium brevitol (0.01 mg/g). Blood was collected by cardiac
puncture, using a heparinized syringe and 23 gauge needle. Whole
blood was diluted 1 to 2 in 8% perchloric acid to precipitate proteins
and then centrifuged. Samples were analyzed for lactate content using
a colorimetric assay from Sigma Diagnostics.
Ventilation rate was measured in 15 animals at several intervals
during estivation. If an animal was positioned in a flow-through
chamber such that its mouth was near the excurrent port, ventilation
could be detected by a rapid and extreme change in the fraction of
oxygen in the excurrent air. This could be measured accurately only
for large animals.
Lipid Stores
In 1984 eight to ten adult S_. lacertina were collected bimonthly
from Orange Lake, Alachua County, Florida, and frozen for later
analysis. Orange Lake is a relatively permanent body of water;
therefore, lipid stores of these specimens were not affected by
periodic droughts. In March of 1986 nine juvenile S_. lacertina (3.6
to 25.5 g body mass) were collected and frozen. Unfortunately, it was
impossible to collect significant numbers of juveniles year round.
Animals were later thawed, weighed, macerated in a tissue homogenizer
with 70Í ethanol and dried to a constant mass. The dry tissue was

13
weighed and each sample was extracted several times with petroleum
ether at 35°C to remove all lipids (Martof 1969). Samples were dried
once more and reweighed. Total body lipid content was calculated for
each animal by subtracting lean dry mass from total dry mass.
Results
Sirenids that were induced to estivate behaved similarly
regardless of size, species or time of year. When placed in saturated
soil, they burrowed into the substratum using their snout as a
shovel. As long as the soil was saturated with water, each animal
kept its mouth in contact with the surface, but as the soil dried the
salamanders retreated into the burrow formed by their body
movements. In some cases an opening was maintained with the surface,
but in several containers the opening collapsed and was filled as the
soil dried. Animals survived for several months in soil regardless of
whether burrows were open or closed. When they were removed for
metabolic measurements, the salamanders often made a sudden jerky
movement, emitted a yelping sound and ventilated by gulping three or
four times. All animals became still soon after handling ceased.
During estivation the gills atrophied and the entire body of an
estiva tor became covered with layers of dead epithelial cells.
Metabolic Rates
•
The mass-specific rate of oxygen consumption (Vn /M)
u2
was inversely correlated with body size (y = -11.37x + 50.4,
2
r = 0.7992; Fig. 2-1). Mass-specific metabolic rate

FIG. 2-1. Rate of oxygen consumption (pi Oo/g’h STPD) of estivating P_. striatus (open circles)
and S. lacertina (closed circles) of different body mass. All measurements were made
at 23°C between day 25 and day 30 of estivation.

LOG MASS (g)
RATE OF 02 CONSUMPTION Oil 02/g-h)
ST

16
(Vn /M) decreased with time in estivation for sirenids of all sizes
2
(Figs. 2-2, 2-3, and 2-4). Time of year had no effect on metabolic
rate during estivation. The effect of sex on metabolic rate is
unknown because it was difficult to determine the sex of individuals
externally. Larval S_. lacertina (under 2 g mass) had rates of oxygen
consumption that appeared similar to rates of P_. stria tus of similar
body size (Fig. 2-2); however, the sample sizes were too small for
statistical comparison. By day 60 of estivation, the Vn /M for these
smallest sirenids had decreased to 24.5 ± 1.2 ul 02/g*h (mean ± S.E.),
a reduction of 56? from the mean rate of 53.6 ± 2.4 ul 0£/g‘h at day
•
18. A similar decrease in Vn /M was seen in the other size groups of
u2
estivating sirenids. Juvenile sirenids (6-110 g) measured near day 60
•
of estivation had a mean V~ /M (18.0 ± 3.0 ul 0£/g*h) that was 59.7?
2
lower than the mean rate during the first two weeks of estivation
(44.7 ± 5.8 ul 02/g*h). Mean VQ /M of adult S_. lacertina measured
over the same two month interval decreased 63.9? (from 30.5 ± 5.9 ul
02/g*h to 11.0 ± 0.7 ul 02/g*h). In all size classes the greatest
•
decline in Vn /M occurred during the first two months of estivation
u2
and leveled off with only a slight decrease thereafter.
•
The Q10 (mean ± S.E.) for VQ /M in estivating S_. lacertina was
2.1 ± 0.1 for seven animals measured at 23°C and 32°C. Whole blood
lactate levels in estivating S_. lacertina were low (0.58 ± 0.13
mmol/1; mean ± S.E.), indicating that metabolism in these animals was
predominantly aerobic. Ventilation rate decreased from 5 to 12
breaths per hour during the first week of estivation, to one or less
breaths per hour by day 300.

FIG. 2-2. Rate of oxygen consumption (STPD) of estivating P_. stria tus (closed circles) and larval
S. lacertina (open circles) weighing less than 5 g. Measurements were made at 23°C.

00

FIG. 2-3. Rate of oxygen consumption (STPD) of estivating juvenile S_. lacertina weighing 6-
110 g. Measurements were made at 23°C.

60
3
Z 40
O
H
Ql
LU
I-
<
oc
0
40 80 120
NUMBER OF DAYS IN ESTIVATION
l>0
o
0
1
160

FIG. 2-4. Rate of oxygen consumption (STPD) of estivating adult S_. lacertina weighing 282-
1061 g. Measurements were made at 23°C.

RATE OF 02 CONSUMPTION Oil 02/g-h)
NUMBER OF DAYS IN ESTIVATION

23
Lipid Stores
Lipid stores varied seasonally in adul t S_. lacertina (Fig.
2-5). Females had the largest percentage of dry mass as lipid in the
fall whereas fat stores of males peaked in the summer. Both sexes had
the lowest total body lipid content from January through March. The
total body lipid content expressed as a percentage of dry mass for all
adult animals examined (n = 56) was 7.6 ± 1.0 (mean ± S.E.). Mean dry
mass in these animals was 20.4% of total wet mass; therefore, average
lipid content was 1.6% of wet mass. Juvenile S_. lacertina collected
in March had a total body lipid content of 5.4 ± 1.8% (mean ± S.E.);
this amount was not significantly different from that of adults
collected during the same month (2.7 ± 0.6%; t = 1.51, p > .05).
Discussion
Sirenid salamanders conserve energy during drought-triggered
estivation by becoming inactive and by substantially reducing their
metabolic rate. Aquatic Siren and Pseudobranchus are capable of
trimodal respiration, exchanging gases across branchial, cutaneous and
pulmonary respiratory surfaces. The partitioning of gas exchange in
aquatic sirenids is dependent upon body size, ambient gas tensions,
temperature and the activity level of the animals (Guimond and
Hutchison 1973; U1tsch 1976b; Wakeman and U1tsch 1976). In Florida,
typical sirenid habitats are shallow, plant-choked waters that are
often hypoxic and hypercapic. Under these conditions, sirenids rely
largely upon their lungs for both 0^ uptake and removal of

FIG. 2-5. Seasonal changes in total body lipids (mean percentage of dry mass) of adult S_.
lacertina collected bimonthly. Females are represented by open circles and males by
closed circles. 8ar length represents two standard errors of the mean.

CO
CO
<
30 -
>-
CE
O
U.
O
CO
g
GL
_l
>-
Q
O
m
_i
<
f—
o
20-
10-
Pi
?
4
—i 1 1 r—
Nov Jan March May
MONTH
I
r\j
<_n
—r~
July
—r~
Sept

26
COp (Guimond and Hutchison 1973; U1 tsch 1975a). The lungs of S_.
lacertina are nearly two-thirds of the body length and are septate and
infolded, thus providing a large respiratory surface area (Guimond and
Hutchison 1973). These effective lungs provide for gas exchange when
sirenids retreat into the substratum during drought. While the soil
is still saturated with water, these salamanders must breathe at the
surface, but as the soil dries the animals can retreat deeper into the
substratum. Because the gills atrophy during estivation and the layer
of dead epithelial cells covering the body probably impedes cutaneous
respiration, the lungs may become the primary site of gas exchange.
In very porous soil, such as sand or sandy loam, interstitial spaces
allow sufficient gas diffusion such that an opening to the surface
need not be maintained. Seymour (1973b) found that gas concentrations
in sandy soil next to buried spadefoot toads were close to atmospheric
levels even at a depth of 70 cm. Sirenids estivating in the
laboratory at 23°C did not need an opening to their burrows; however,
at higher temperatures or in less porous soil an opening to the
surface may be needed for gas exchange.
Estivating sirenids move very little unless they are disturbed by
handling. Most estiva tors moved suddenly when touched and then became
motionless again, but few attempted to crawl away. These animals
appeared to be in a state of light torpor similar to that described
for the estivating lungfish Protopterus aethiopicus (Delaney et al.
1974) and for estivating mammals (Hudson and Bartholomew 1964). This
ability to respond to external stimuli during estivation could aid in

27
avoidance of predation, particularly because sirenids often couple
their sudden jerky movements with a startling yelping noise.
The rates of oxygen consumption measured at the onset of
estivation are close to the resting rates measured by Ultsch (1976a)
for aquatic S_. lacertina and P_. stria tus of the same body size. The
metabolic rates of sirenids of all sizes decline gradually during the
first two months of estivation and then reach a plateau that is 60 to
70% lower than the rate at the onset of estivation. Gehlbach et al.
(1973) measured V /M at 25°C in aquatic and estivating S_. intermedia
U2
from Texas, but they reported rates that were nearly three times as
high as those of estiva tors measured in this study and aquatic animals
measured by Ultsch (1976a). It is possible that these S_. intermedia
were not at rest when rates of oxygen consumption were measured.
Even though ventilation rates decreased dramatically as
estivation proceeds, lacertina relied primarily on aerobic
pathways. Mean blood lactate levels for estivating S_. lacertina (0.58
± 0.13 mmol/1) were similar to those of Scaphiopus hammondii resting
on the surface (Seymour 1973c).
Several species of frogs and a species of lungfish that estivate
in response to drought show a decrease in metabolic rate similar to
that of sirenids (Table 2-1). The rate of this decline varies among
these species. In the frog Lepidobatrachus llanensis VA /M drops
2
nearly 80% after only seven days of dormancy (McClanahan et al. 1983),
whereas a drop of 32% is evident after 25 days in dormant Scaphiopus
couchii (Seymour 1973b). These differences may reflect different
environmental conditions in the habitats where these species occur, or

23
TABLE 2-1
Oxygen Consumption Rates of Estivating Amphibians
and Lungfish (Protopterus) at 23-25°C
•
Minimum VQ /M
during Dormancy
(yl 02/g‘h)
Species (Mass)
Resting V /M
2
(yl 02/g*h
Reference
Lepidobatrachus
llanensis
("52-11$' g)
97
20
McClanahan et al.
1933
Pyxicephalus
adspersus
TTCTJSTg)
37
10
Loveridge and
Withers 1980
Scaphiopus
couchi
51
11
Seymour 1973a
(x=20 g)
Cyclorana
platycephal us
156
45
van Beurden 1980
(x=14 g)
Protopterus
aethiopicus
(4100 kg)
25
5
Oelaney et al. 1974

29
differences in the way that estivation/dormancy was induced in these
separate studies, Rate of dehydration, for example, could affect the
time frame of a change in metabolic rate. Unfortunately, the
physiologial mechanisms involved in the reduction of metabolic rate in
these dormant ectotherms are unknown. Although starvation alone has
been shown to reduce the metabolic rate of many vertebrates including
reptiles (Benedict 1932; Belkin 1965), lungfish (Delaney etal. 1974)
and frogs (Hill 1911), the pathways that mediate this effect are
unclear. Even less is known about the direct effects of desiccation
upon metabolism. Changes in the metabolic rate of estivating sirenids
may be related to thyroid function. Siren lacertina that had been
estivating for eight months had circulating levels of thyroxine that
were significantly lower than the plasma thyroxine levels of active
animals (Etheridge, unpublished data). However, no experimental
evidence exists to indicate that the reduction in metabolic rate seen
in estiva tors is thyroid mediated.
One common thread appears in the comparison of V /M of
U2
estivating amphibians and lungfish; the minimum Vn /M during dormancy
U2
for each species is similar (Table 2-1). When the data for each
species are adjusted for body size and temperature, the
minimum V„ /M of estivators is between 10 and 20 yl Oo/g’h for each
u2
species. Resting V~ /M for the same group of species varies much
u2
more, ranging from 37 to 150 yl 0£/g*h. This consistency of the
lowest V, /M may indicate that these rates represent the minimum cost
2
of existence for these ectotherms. In these animals resting metabolic
rates appear to be the "idling speeds" when resources (i.e., food and

30
water) are abundant. In animals that become dormant these "idling
speeds" can be reset 60-80% lower.
The amount of time an animal can survive without food is
dependent upon its rate of energy consumption and upon the amount of
stored energy the animal can utilize. For estivating sirenids the
most important determinants of metabolic rate are body size, length of
time in estivation and body temperature. The energy stores of each
animal will vary with time of year and possibly with body size.
The number of days estivating sirenids could survive without food
was estimated by calculating energy stores and rates of energy
consumption for animals of various sizes and lipid content (Table
2-2). The higher mass-specific metabolic rate of the smaller
salamanders results in a more rapid depletion of stored energy than in
the larger animals. A 1 g animal would deplete its energy reserves
1.5 times as fast as a 500 g animal even if both began estivation with
the same body composition (Table 2-2). Increasing environmental
temperatures would cause more rapid depletion of energy stores;
conversely, lower burrow temperatures would prolong the length of time
an animal could estivate. The Q1q of estivating S_. lacertina (Q^ =
2.1) is essentially the same as that reported by Guimond and Hutchison
(1973) for aquatic S_. lacertina (Q^g = 2.2).
Differences in total body lipid stores at the onset of estivation
would also contribute to differences in potential survival time. The
greater total caloric content of a 500 g S_. lacertina with lipid
stores totaling 20% of its dry mass (the mean lipid content for
females in fall) would allow it to survive 40 days longer without food

TABLE 2-2
Energetics of Estivation in Sirenid Salamanders (at 23°C)
An ima1
Wet Mass
(g)
Dry Lipid
mass (g)
Dry Lean
mass (g)
Energy
Availabled
Energy
Costsd
Potential
Survival
KCAL
Lipids
KÃœAL
Lean
Day 1-60
KCAL/Day
After Day 60
KCAL/0ay
Number
Days
Ia
1
0.01
0.18
0.1
0.4
0.004e
0.003e
146
2b
500
7.8
94.2
57.5
197.8
0.961f
0.607f
386
3C
1125
86.0
134.0
877.4
324.5
2.160f
1.366f
842
NOTE: Ory mass averaged 20.4$ of wet mass for freshly caught sirenids.
a Hypothetical sirenid representing the smallest size class (P_. striatus and larval lacertina).
For comparative calculations, lipid content is assumed to be 7.6% of dry mass.
b Hypothetical adult S_. lacertina assumed to have mean lipid content of 7.6%.
c Based on data from an individual female caught November 1984. This animal had a total body lipid
content that was 43% of its dry weight.
d Assumptions: 1. Maximum lean tissue metabolized is 50%; maximum lipid metabolized is 80% (Martof
1969). .
2. Oxidation of lipids yields 9.3 kcal/g; oxidation of lean tissue yields 4.2 kcal/g.
3. Mean of 4.6 kcal/liter 02 consumed.
•
e Mean Vn /M for this size class was 35.2 M1 /g*h during the first 50 days of estivation, and 23.5
u2
M1 /g*h thereafter.
f
Mean V /M for sirenids in this class size was 17.4 pl/g*h during the first 60 days and 11.0 U1 /g*h
U2
thereafter.

32
than a 500 g estiva tor with lipid stores comprising only 3% of its dry
mass (the mean lipid content for summer animals). A very large $_.
lacertina with a large quantity of stored lipid, such as the 1125 g
female with 43% body lipid (Table 2-2), potentially could survive two
to three years without food. Even a 1 g si reñid could survive for
several months (Table 2-2) on stored energy, and in most cases Florida
droughts last only a few weeks or months. Hence, during an average
drought, most of the sirenids in a population may be able to survive
by estivating. In a prolonged drought, however, the continuation of a
population of sirenids at a given site may be dependent upon the
survival of a few large individuals with greater than average lipid
stores.

CHAPTER III
WATER BALANCE DURING ESTIVATION
Introduction
When an amphibian remains inactive in a burrow energy stores
decline because energy cannot be replenished until the animal can
emerge and feed. Body water fluxes are more complex, because water
can be gained or lost at several sites (Fig. 3-1). In amphibians
water can be lost by evaporation from the respiratory surfaces, via
urine, or across the skin. Most vertebrates must eat or drink to
replenish body water, for their only source of water gain during
prolonged inactivity is the very slight amount of metabolic water that
is formed when foodstuffs are oxidized. Amphibians, on the other
hand, can take up water across their permeable skin (for review see
Duellman and Trueb 1986) and many can reabsorb water from their
urinary bladder (e.g., Ruibal 1962; Main and Bentley 1964; Bentley
1966). In addition, amphibians and lungfish that estivate burrow into
the soil to avoid desiccating surface conditions and employ various
strategies to maintain water balance.
One strategy involves increasing resistance to water loss as much
as possible by forming an impermeable "cocoon." In estivating African
lungfish (Protopterus) this cocoon is composed of dried mucus (Kitzan
and Sweeney 1963), but in most estivating amphibians studied thus far
electron microscopy has revealed the cocoon to be composed of multiple
33

FIG. 3-1. Pathways of water exchange in an estivating amphibian.

WATER GAIN
Metabolic Wafer
Soil Water
Bladder Water
WATER LOSS
-> Respiratory
> Soil
Co
cn
* Urine

36
layers of unshed epithelial cells (Lae and Mercer 1967; McClanahan et
al. 1976; Loveridge and Craye 1979; RuiDal and Hillman 1981). In two
anurans, Pyxicephalus adspersus (Loveridge and Withers 1980) and
Lepidobatrachus llanensis (McClanahan et al. 1976), the cocoon of
estivators reduces water loss so effectively that these animals can
survive for several months in dry soil with little change in
concentrations of their internal solutes.
A second strategy for water balance during estivation has been
described for spadefoot toads. These animals maintain a favorable
water potential gradient with moist soil such that water is absorbed
from the soil across the skin. Scaphiopus hammondii can decrease
their body water potential to levels as low as -15 bars and thus
absorb water from any soil with a higher water potential (Ruibal et
al. 1969). Spadefoot toads maintain these low water potentials
primarily by accumulating urea in their plasma, thereby greatly
increasing their osmotic potential without disrupting ion balance
(McClanahan 1967, 1972; Shoemaker etal. 1969).
The objectives of this portion of the study were to investigate
adaptations that allow S_. lacertina and P_. stria tus to survive the
dehydrating conditions of drought and to compare these adaptations to
those of other estivating amphibians. One specific area investigated
was the way in which these animals maintain water balance during
estivation, that is, whether they become water-resistant or exchange
water with the soil. The contribution of the urinary bladder to water
balance and the effect of estivation on plasma and urine solute

37
concentrations were determined. In addition, the effects of body size
and soil water potential on potential survival time were studied.
Materials and Methods
Siren lacertina and P_. stria tus were collected and induced to
estivate in the laboratory as previously described. These estivators
were maintained in moist soil (5 to 12% water content) so that plasma
parameters would reflect a hydrated state. Blood and urine samples
were collected from three S_. lacertina on day 210 of estivation and
from five S_. lacertina on day 260 of estivation. Concurrently, blood
samples were taken from 13 freshly caught, aquatic S_. lacertina. An
attempt was made to collect urine from the aquatic animals as well.
Animals were maintained at 23°C for all experiments.
Animals were anesthetized with sodium brevitol (0.01 mg/g) and
blood was collected by cardiac puncture using a heparinized syringe
and a 23 gauge needle. Each blood sample was centrifuged, the
hematocrit determined and the plasma frozen for later analysis. Urine
was collected by palpating the area of the urinary bladder; these
samples were frozen immediately. To estimate the volume of urine held
in the bladder of each estiva tor, animals were weighed before and
after urine was expressed.
Plasma and urine samples later were thawed for the following
analyses. Sodium and potassium concentrations ([Na+], [K+]; meq/1)
were determined for 5 yl samples using an Instrumentation Laboratory
443 Flame Photometer. Urea and ammonia concentrations ([NH^], [NH*];
mmol/1) were determined using the colorimetric Berthelot method (Sigma

33
test kit 640). Chloride concentration ([Cl-]; meq/1) was determined
for 10 yl samples using a Radiometer CMT 10 Chloride Titrator. A
Wescor 5100 B Vapor Pressure Osmometer was used to determine the total
osmotic concentration (m0sm/kg) of 5 U1 samples. A one-tailed
Students t-test was used to compare sample means of estiva tors and
active animals for each parameter.
Rates of water loss and gain were measured for estivating S_.
lacertina (3-550 g body mass) and estivating P_. stria tus (less than
2 g) in soils of varying water content. The soil used for these
experiments was obtained from typical sirenid habitat in Alachua
County, Florida. Mechanical analysis of this soil established the
composition as 92.662 sand (primarily 0.25-0.50 mm particle size),
4.522 silt and 2.322 clay. This soil was mixed thoroughly and
filtered through a screen (1 mm mesh) to remove debris. A
characteristic moisture curve for this specific soil was constructed
by beginning with saturated soil and then measuring water potential
and water content at several intervals as the soil dried slowly in
room air. Water potential (- bars) was measured with a ceramic tip
tensiometer. Soil water content was determined by weighing the
sample, drying it to a constant mass and then reweighing it. The
percent of mass lost during drying represented the percent of water
content by mass. Once the characteristic moisture curve was
established the soil water potential of any sample of this soil could
be determined by calculating percent water content.
Large plastic containers (50 x 39 x 20 cm) were set up to hold
soils of three different moisture contents (0.72, 5.02 and 6.02

39
water). Air dry soil (0.7? water) was used to simulate the most
dehydrating possible field conditions. Preliminary observations
indicated that estiva tors maintained mass in soil with greater than
7.0? water content; therefore, slightly drier soils (5.0? and 6.0?
water content) were used to establish the point at which estiva tors
began to lose water to soil. Each container was tightly covered and
the water content of the soil was checked periodically to insure
stability. Salamanders estivating for seven months or more were used
for this experiment. Estiva tors had been maintained in moist soil
(10-12? water content) to insure maximum hydration before these
experiments. They were then exposed to the most dehydrating soil
(0.7? water content). After this they were exposed to the soils of
different water content in the following order: 5.0?, 0.7? and
6.0?. Each animal was weighed and then buried in the soil with only
its head exposed. Respiratory water loss was assumed minimal because
estiva tors ventilate only once or twice each hour. After two hours
the animal was excavated, any soil adhering was carefully brushed off,
and the animal was reweighed. All mass changes were recorded as water
lost or gained (mg/g body mass * hour). Data from animals that moved
or urinated (as indicated by any moisture around the cloaca) during
the experiment were discarded. The protocol was designed to maximize
the rates of water exchange by putting hydrated salamanders into
dehydrating soil for measurements of water loss, then moving these
dehydrated animals into soil with a higher water potential to
determine rates of water uptake. For example, animals were placed in

40
tne driest soil (0.7$ water) to dehydrate them prior to exposure to
the soil with 6% water content.
The tail tip of an estivating S_. lacertina (day 210) was removed
and examined to determine the structure of the cocoon. The tissue was
fixed in 10$ neutral buffered formalin, transferred to 70$ ethanol and
then prepared for paraffin embedding. The tissue was sectioned at
10 ym, stained with Alcian Blue and counter-stained with Hematoxylin
and Eosin (Humason 1972) for examination by 1ight microscopy. Because
Alcian Blue stains mucopolysaccharides, it was used to indicate
whether mucus was a major component of the cocoon. Hematoxylin stains
nuclear material; hence, it was used to determine the presence or
absence of cells in the cocoon layer.
Rasults
The body position of estivating sirenids is such that most of the
surface area of the animal is in direct contact with the surrounding
soil. Siren lacertina do not coil, but maintain a somewhat S-shaped
configuration. In some individuals the tail was curled forward with
the tip touching the body. Estivating P_. stria tus were usually curled
into a figure eight with the head resting near the tail.
Blood parameters of S_. lacertina estivating 210 days were not
significantly different from those of animals estivating 260 days;
therefore, these data were pooled for comparison with the aquatic
animals. Plasma ion concentrations ([Na+], [K+], [Cl-]) were not
significantly different between the two groups (Table 1). However,
plasma urea concentration was significantly higher in the estivators

TABLE 3-1
Solute Concentrations of Plasma from Active S. lacertina and of
Plasma and Urine from Estivating S. lacertTna (Mean ± S.E.)
Sodium
(meq/1)
Potassium
(meq/1)
Chloride
(meq/1)
Urea
(mmol/I)
Ammonia
(mmol/I)
Other'1
Total
(mOsm/kg)
Active Animals
PLASMA (n=13)
119.0±2.2
3.8±0.2
73.U3.3
7.8±1.5
2.410.2
13.2
229.3111.7
Estivators
PLASMA (n=3)
113.0±4.5
3.8±0.4
71.9±4.6
49.115.0
4.210.9
22.2
264.219.3
Estiva tors
LJRIME (n=3)
11.3l6.7
8.911.8
6.012.5
63.617.4
45.7110.2
45.0
130.5125.3
a Other = plasma proteins, Ca++, Mg+, glucose, HCO3, etc. This component makes up the difference
between the total concentration and the summed concentrations of measured solutes.

42
(t = 9.39, p < .001) as was the total plasma osmotic concentration (t
= 3.89, p < .005). The mean hematocrit was higher in estivators (33.9
± 3.9%) than in active animals (26.1 ± 2.7%), but the difference was
not statistically significant (t = 1.55, p > .05).
No urine could be expressed from any active Siren despite
numerous attempts. Estivating sirenids were never observed to void
urine unless disturbed by handling. Urine collected from 10
estivating S_. lacertina (mean mass of 479.7 ± 41.2 g) made up 5.3 ±
0.8% (mean ± S.E.) of the mass of these animals. The maximum amount
of stored urine measured was 10.1% of body mass. Urine collected from
estivators was hyposmotic in comparison to the plasma (Table 3-1).
Concentrations of Na+ and Cl" were significantly lower in urine than
in plasma (t = 18.4, p < .001; t = 2.21, p < 0.05), whereas the
concentration of K+ was slightly higher in urine (t = 2.53,
p < 0.025). Urea concentration was not significantly higher in the
urine (t = 1.51, p > 0.05). Levels of ammonia were very low in the
plasma of both aquatic (2.4 ± 0.2 mmol/1) and estivating (4.2 ± 0.9
mmol/1) S_. lacertina. Ammonia concentration in the urine of
estivators was ten times that in the plasma (45.7 ± 10.2 mmol/1).
Soil water potential of the sand used in these experiments
remained high (between 0 and -1 bars) when soil water content was
greater than 8% (Fig. 3-2). At soil water contents below 6% the water
potential of this soil begins to increase exponentially with slight
decreases in water content. The rate of water exchange with the soil
was related to body size of the salamanders. This relationship was
strongest in the driest soil (Fig. 3-3), where it can be related as a

FIG. 3-2. Characteristic moisture curve for soil used in water
exchange experiments.

WATER POTENTIAL (-bars)
-P»
-P*

FIG. 3-3. Rates of water loss for estivating S. lacertina in soil
with Q.7% water content (closed circles) and in soil with
5.0% water content (open circles).

46

47
power function (y = 215x-^*^, r^ = 0.96). Two 1 g P_. stria tus placed
in this same soil (0.7% water content) lost water at rates of 51 and
92 mg/g'h. Six of 14 animals maintained their original mass in the
soil with 5.0% water content; the other eight lost mass, but at a much
lower rate than in the drier soil (Fig. 3-3). Similarly, 4 of 13 S_.
lacertina maintained their weight in the soil with 6.0% water content,
and the remainder gained water from this soil (Fig. 3-4). Thus, a
positive water balance is achieved by estiva tors in soil with water
potential greater than -5 bars (6% water content), whereas estivators
in drier soil (i.e., 5% 1^0 content, less than -5 bars) may lose water
(Fig. 3-4).
Light microscopy revealed the dry outer layer or "cocoon" of
estivating S_. lacertina to be composed primarily of dead, squamous
epithelial cells. This layer did not stain for mucopolysaccharides as
it would if mucus were the primary component, but remained brown in
color. In a few animals that were allowed to dehydrate in dry soil,
the cocoon appeared to be thicker than in hydrated estivators.
Discussion
The long cylindrical body shape of sirenid salamanders results in
a relatively high surface to volume ratio. While this may be
advantageous for cutaneous respiration in water, it is disadvantageous
during a drought because it creates a large surface area for water
loss. Siren lacertina are fairly stout animals with a thick, muscular
body wall and tightly wrapped skin, and they are incapable of coiling
up to reduce surface area. Pseudobranchus striatus are more slender

FIG. 3-4. Rates of water exchange with the soil for estivating S_.
lacertina in soil with 5.0% water content (closed circles)
and in soil with 6.0% water content (open circles).

100 200 300 400 500 600
MASS (g)
CHANGE IN MASS (mg/g-h)
i i i i i i
ojoi â– &'G}N>_i.o-iroco

50
and can coil somewhat, but most of the surface area of both species is
in direct contact with soil during estivation. Consequently, water
exchange with the soil is the most important factor in water balance
of estivating sirenids. The rate of water exchange with soil is a
function of several parameters, primarily surface area, resistance and
the difference between the water potential of the soil and that of the
animal.
The water potential of an estivating animal is related to the
osmotic potential of its body fluids. An amphibian with high plasma
solute concentrations has lower water potential (- bars) than an
animal with lower plasma solute concentrations, and all else being
equal more water will move across the skin of the first animal. The
water potential of estivating S_. lacertina is increased by urea
accumulated in the plasma. Elevated plasma urea levels in estiva tors
accounted for the difference between total plasma osmolality of
estiva tors and aquatic animals. On the other hand, plasma ion
concentrations appear to be closely regulated. This strategy of
decreasing water potential by storing urea has been demonstrated in
several species of amphibians, including Ambystoma tigrinum (Delson
and Whitford 1973), Xenopus laevis (Balinsky et al. 1967), Bufo
viridis (Degani et al. 1984), and several species of Scaphipus
(McClanahan 1967; Shoemaker et al. 1969; Jones 1980). In these
species plasma ion concentrations increased much less (no more than
two times hydrated levels) than plasma urea levels (up to 30-fold
increase). The difference between the two variables of soil water
potential and water potential of the animal not only determines the

51
direction of water exchange (water moves from an area of higher to
lower water potential), but the rate at which the exchange occurs.
Sirenids lost water in soil with water potentials lower than -5 bars
(5.0% water content), but they lost water more rapidly in the soil
with 0.7% water content (water potential less than -15 bars). The
rate of water loss was greatly affected by the third variable, surface
area of the estivator. Small S_. lacertina and P_. stria tus dehydrated
rapidly due to their high surface to volume ratio. The relationship
of body size to rate of water exchange could be seen most clearly in
the driest soil (0.7% water), where hydric properties of the soil play
the major role in determining water loss. In soils with 5.0 or 6.0%
water content the correlation between rate of water exchange and body
size is less evident. This increased variability in rates indicates
that water exchange in soils of higher water potential may be mediated
more by hydric properties of the animal than by those of the soil.
Variability in rates of water exchange may reflect differences in
water potential of individual animals and/or differences in resistance
to water flux.
Resistance is the fourth variable in determining rates of water
exchange and is the most difficult to measure. Resistance as defined
here is the capacity of the outer layer of the animal to retard water
flux. This involves many factors such as the degree of vasodilation
or vasoconstriction, hormonally mediated processes and physical
properties of the outer layer. A salient characteristic of estivating
amphibians is the outer covering of the animal referred to as the
cocoon, and this is usually the focus of any investigation of

52
resistance to water loss. The cocoon of sirenids examined in this
study appears to be layers of stratum corneum. Examination by light
microscopy revealed flattened, nucleated cells. Furthermore, these
layers do not stain for mucopolysaccharides as they would if mucus
were the main component. These findings differ from those of Reno st
al. (1972) who described the cocoon of estivating intermedia as
layers of dried mucus with no cellular integrity. For sirenids in
this study, the cocoon layer could be peeled off in sheets and
preserved intact, indicating that it is much like a typical sned skin
of any amphibian. McClanahan et al. (1983) described cocoon formation
in Lepidobatrachus llanensis as a normal shedding cycle in which the
layers do not detach from the animals. Water loss in air in cocooned
L_. Ilamensis was reduced as much as 70% after one week of estivation
(McClanahan et al. 1976) and was further reduced with each additional
layer of stratum corneum added to the cocoon of these frogs during
estivation (McClanahan etal. 1983). Unfortunately, the degree to
which the cocoon retards water flux in soil has not been measured for
any estiva tor. These types of measurements are difficult to make, and
there is the further complication of trying to separate the
contribution of the cocoon from the other factors involved in
resistance. Using an in vitro technique, Reno et al. (1972) measured
the effect of the cocoon of S_. intermedia upon water uptake from agar
blocks and found that the cocoon alone decreased water uptake by
31%. Dehydrated Siren did appear to have a thicker cocoon layer than
hydrated estivators, and it may be that resistance is varied by
increasing the rate of shedding; however, this warrants further study.

53
Amphibians from different environments may respond differently to
drought depending upon the type of soil in which they burrow. The
strategy employed by sirenids, spadefoot toads and others of storing
urea and absorbing water from the soil may be useful only in sandy
soils, where large interstitial spaces cause high water potentials
even at low moisture contents. Frogs that become almost waterproof,
such as P_. adspersus and l_. llanensis, may live where soils have a
high clay content. Clay soils have small pore size and consequently
low water potential even at high moisture content (Noble 1974). Thus
amphibians burrowed in this type of soil may not be able to reduce
their water potential below that of the soil; they therefore avoid
dehydration by becoming as impermeable to water loss as possible. The
possibility that amphibians can vary resistance according to the water
potential of the soil in which they burrow warrants additional study.
Several estivating amphibians store large quantities of dilute
urine when in positive water balance and later reabsorb water from the
bladder to rehydrate body fluids during drought (e.g., Ruibal 1962;
Bentley 1966). In some fossorial desert frogs, bladder volumes may
account for as much as 50% of the animals' body mass (Bentley 1966).
Siren lacertina can reabsorb water from its bladder (Bentley 1973).
No urine could be collected from aquatic animals, possibly because
active sirenids excrete urine continuously. Urine expressed from
hydrated estiva tors averaged 5.3% of body mass, and a maximum of 10.0%
of body mass was measured for one animal. These values are lower than
those reported for most other estivating amphibians, but are higher
than the values of 1 and 2% reported for the aquatic amphibians

54
Xenopus laevis (Bentley 1966) and Triturns crista tus (Bentley and
Heller 1964). Sirenids may be morphologically constrained to low
bladder volumes; they are long and cylindrical and their tight skin
and thick body wall do not allow for a very distensible body cavity
like that of most frogs. However, even a water reservoir of 5 to 10%
of body weight would extend survival time.
The length of time estivating sirenids could survive without
reaching lethal dehydration levels is dependent primarily upon body
size and soil water potential. In very dry soil (0.7% water content)
a 20 g S_. lacertina losing water at a constant rate would lose 50% of
its body mass as water in 16 h. This level of water loss is lethal
for most amphibians (Ray 1953). A 500 g animal under the same
conditions would last 125 h. In soil with a water potential
approaching -5 bars (5.0% water content for the soil used in these
experiments) the 20 g animal would reach 50% dehydration in 272 h (11
days); the 500 g animal would last 594 h (29 days). Under field
conditions the rates of water loss would decrease as the soil around
the animals gained water (and increased in water potential) and as the
animals' water potential decreased due to dehydration. Thus actual
survival times would be longer, although a larger animal would still
survive longer than a smaller one in the same soil. Gehlbach et al.
(1973) reported that S_. intermedia lost 26-28% of their body mass
during 16 weeks of estivation; however, these animals were in soil
that was allowed to dry out. Sirenids estivating in soil with water
potential equal to or greater than their body water potential would
not lose water to soil. Under such conditions the only mass loss

55
would be due to metabolized tissue, and sirenids could survive as long
as energy stores persisted. Under field conditions it may be rare for
water to be the limiting factor in survival during estivation. In
Florida brief showers occur even during severe droughts, and although
these showers do not reflood the habitat, they may suffice to moisten
the soil such that sirenids can maintain a positive water balance.
Furthermore, water potential can vary greatly from site to site
depending upon such factors as soil type, plant cover and proximity to
the water table. For example, sandy soil within a meter of the water
table would remain virtually saturated due to capillary action, even
during a drought. Sirenids in such a place would not be in danger of
dehydration and could serve to re-establish populations at sites that
did reach critical water tensions during drought.

CHAPTER IV
SUMMARY AND CONCLUSIONS
Throughout the southeastern coastal plain of the United States
there is an abundance of shallow water habitat suitable for sirenid
salamanders. This is often a transient resource, however, because
drought is common in this region. Sirenid salamanders, although
aquatic, are well-adapted for survival during drought and thus can
exploit impermanent bodies of water. As their habitat dries out,
sirenid salamanders burrow into the substratum and remain inactive
until the area is reflooded. Survival during estivation is due to
their abilities to live for prolonged periods on stored energy and to
maintain water balance in drying soil.
Energy is unlikely to be the limiting factor in sirenid survival
during estivation except in rare cases. The metabolic rates of
estivating S_. lacertina and P. stria tus are reduced 60 to 70* below
rates of resting aquatic sirenids. Coupled with substantial energy
stores, these low rates of energy consumption would permit large S_.
lacertina to survive for two to three years without food and would
allow even a 1 g animal to survive for several months. In a prolonged
drought the largest animals with the greatest energy stores may be the
only survivors, but these could serve to found a new population.
Water is more likely to be limiting to survival than energy, but
under usual field conditions lethal dehydration of estivating sirenids
55

57
is probably rare. The cocoon of lacertina, composed of dead
epithelial cells, may retard water exchange (Reno et al. 1972), but it
does not make estiva tors impermeable to water loss. Si reñid
salamanders exchange water with soil at a rate that shows a strong
inverse correlation with body size, indicating that relative surface
area is a major factor in water balance. The other major determinant
of the rate and direction of water flux is the magnitude of the
difference in water potential of the soil and water potential of the
esti va tor.
Water potential of an animal buried in soil is dependent
primarily upon the concentration of internal solutes in the animal's
body fluids. Siren lacer tina that had been estivating seven or more
months had a mean plasma osmotic concentration of 264.2 ± 9.8 mOsm/kg,
which is the equivalent of -5.8 bars of water potential. Most animals
maintained a positive water balance in soil with water potential
greater than -5.7 bars, but began to lose water in soil with water
potential lower than this. Aquatic S_. lacertina had a lower mean
plasma osmotic concentration (229.8 ± 11.7 mOsm/kg), the equivalent of
-5.0 bars of water potential, and would lose water in soil with a
higher content than would estivators. This difference in osmotic
concentration is due to the higher plasma urea concentration of the
estivating S_. lacerti na. The salamanders used in this experiment had
been kept in moist soil and were hydrated; it is possible that plasma
urea concentrations can be increased in estivators as they become
dehydrated, decreasing their water potential even further. This has
been wel1-documented in species such as Scaphiopus couchii

58
(McClanahan 1972), which can actively increase urea concentrations in
body fluids in response to decreasing soil water potential.
Water potential of soil is dependent upon the soil structure and
composition (i.e., percentages of sand, silt and clay) and upon the
water content (Fig. 4-1). Clay has smaller pore sizes than sand,
higher matric potentials, and consequently, much higher water
potential than sand at any given water content. Thus, a siren
estivating in clay would be in a potentially more stressful hydric
environment than one in sand. It may be that sirenid salamanders can
inhabit drought-prone waters only in areas of sandy soil. This could
help to explain the geographic distribution of sirenids, which live
primarily in the coastal plain, where soils tend to be sandy. Even
within a large area such as the coastal plain soil type varies, and
there may be areas within this mosaic that are unsuitable for sirenid
estivation. Hence, sirenid distribution may be affected by soil type
as well as water availability.
Although the physiological mechanisms associated with estivation
seem to be evolutionarily conservative among amphibians, many of these
adaptations are not present in other vertebrates. Indeed, in many
ways amphibians such as sirenid salamanders are uniquely suited to
survival during drought. Rates of energy consumption are low in
amphibians, particularly salamanders, even in comparison to reptiles
(Pough 1983). Other vertebrates must rehydrate by drinking or eating;
amphibians can absorb water from moist soil and store excess water in
the bladder for later use. Lastly, the ability to tolerate high
concentrations of urea in body tissues has not been demonstrated for

FIG. 4-1. Hypothetical water potentials of different soil types at
varying water content. (See Noble 1974 for a review of
soil water potentials.)

60

61
any of the higher vertebrates. Ironically, the highly permeable skin
of amphibians, which would appear to be a disadvantage in xeric
conditions, is actually highly advantageous (e.g., Bentley 1966;
McClanahan 1972). Even though amphibians cannot maintain prolonged
surface activity during drought, they can survive for months or years
in the absence of food and free water, a feat well beyond the
abilities of any endotherm. In the case of sirenid salamanders, the
ability to survive drought by estivating allows them to exploit
potentially transient aquatic habitats that would be uninhabitable for
many species.

LITERATURE CITED
Balinsky, J.B., E.L. Choritz, C.G.L. Coe, and G.S. Van Der Schans.
1967. Amino acid metabolism and urea synthesis in naturally
aestivating Xenopus laevis. Comp. Biochem. Physiol. 22:59-63.
Belkin, D.A. 1965. Reduction of metabolic rate in response to
starvation in the turtle Sternothaerus minor. Copeta 1965:367-
363.
Benedict, F.G. 1932. The physiology of large reptiles. Carnegie
Inst. Washington Publ. 425.
Bentley, P.J. 1966. The physiology of the urinary bladder of
amphibia. Biol. Rev. 41:275-316.
Bentley, P.J. 1973. Osmoregulation in the aquatic urodeles Amphiuma
means (the congo eel) and Siren lacertina (the mud eel). Effects
of vasotocin. Gen. and Comp. Endocrinology 20:386-391.
Bentley, P.J., and H. Heller. 1964. The action of neurohypophysical
hormones on the water and sodium metabolism of urodele
amphibians. J. Physiol. 171:434-453.
Bentley, P.J., A.K. Lee, and A.R. Main. 1958. Comparison of
dehydration and hydration of two genera of frogs (Heleioporus and
Neobatrachus) that live in areas of varying aridity. J. Exp.
Zool. 35:577-684.
Brenner, F.J. 1969. The role of temperature and fat deposition in
hibernation and reproduction in two species of frogs.
Herpetologica 25:105-113.
Burch, P.R., and J.T. Wood. 1955. The salamander Siren lacertina
feeding on clams and snails. Copeia 1955:255-256.
Byrne, J.J., and R.J. White. 1975. Cyclic changes in liver and
muscle glycogen tissue lipid and blood glucose in a naturally
occurring population of Rana catesbeiana. Comp. Biochem.
Physiol. 50A:709-715.
Cockrum, L. 1941. Notes Siren intermedia. Copeia 1941:265.
Conant, R. 1975. A field guide to reptiles and amphibians of eastern
and central North America. Houghton Mifflin Co., Boston.
62

63
Davis, W.B., and F.T. Knapp. 1953. Notes on the salamander Siren
intermedia. Copeia 1953:119-121.
Degani, G., N. Silanikove, and A. Shkolnik. 1984. Adaptation of
green toad (3ufo viridis) to terrestrial life by urea
accumulation. Comp. Biochem. Physiol. 77A:585-587.
Delaney, R.G., S. lahiri, and A.P. Fishman. 1974. Aestivation of the
African lungfish Protopterus aethiopicus: Cardiovascular and
respiratory functions. J. Exp. Biol. 61:111-128.
Delson, J., and W.G. Whitford. 1973. Adaptations of the tiger
salamander, Ambystoma tigrinum, to arid habitats. Comp. Biochem.
Physiol. 46A:631-638.
Duellman, W.E., and L. Trueb. 1986. Biology of amphibians. McGraw-
Hill, Inc., New York.
Fitzpatrick, L.C. 1976. Life history patterns of storage and
utilization of lipids for energy in amphibians. Amer. Zool.
16:725-732.
Freeman, J.R. 1958. Burrowing in the salamanders Pseudobranchus
striatus and Siren lacertina. Herpetologica 14:130.
Freeman, J.R. 1967. Feeding behavior of the narrow-striped dwarf
siren Pseudobranchus striatus axanthus. Herpetologica 23:313-
314.
Gehlbach, F.R., R. Gordon, and J.B. Jordan. 1973. Aestivation of the
salamander, Siren intermedia. Am. Mid. Nat. 89:455-463.
Gehlbach, F.R., and S.E. Kennedy. 1978. Population ecology of a
highly productive aquatic salamander (Siren intermedia).
Southwestern Naturalist 23:423-430.
Goin, C.J. 1941. The striped siren, Pseudobranchus striatus (Le
Conte). M.A. thesis, University of Florida, Gainesville.
Guimond, R.W., and V.H. Hutchison. 1973. Trimodal gas exchange in
the large aquatic salamander, Siren lacertina. Comp. Biochem.
Physiol. 46A:249-268. '
Hanlin, H.G., Jr. 1973. Food habits of the greater siren, Siren
lacertina, in Alabama coastal plain pond. Copeia 1973:358-359.
Hill, A.V. 1911. The total energy exchanges of intact cold-blooded
animals at rest. J. Physiol. 43:379-394.

64
Hudson, J.W., and G.A. Bartholomew. 1964. Terrestrial animals in dry
heat: Aestivators. Pages 541-550 in D.B. Dill, E.F. Adolph and
C.G. Wilbur, eds. Handbook of physiology. Williams and Wilkins
Co., Baltimore.
Humason, G.L. 1972. Animal tissue techniques. W.H. Freeman and Co.,
San Francisco.
Jones, R.M. 1980. Metabolic consequences of accelerated urea
synthesis during seasonal dormancy of spadefoot toads, Scaphiopus
couchi and Scaphiopus multipiicatus. J. Exp. Zool. 212:255-267.
Kitzan, S.M., and P.R. Sweeny. 1963. A light and electron microscope
study of the structure of Protopterus annectens epidermis. I.
Mucous production. Cañad. J. Zool. 46:767-773.
Lee, A.K., and E.H. Mercer. 1967. Cocoon surrounding desert-dwelling
frogs. Science 157:87-83.
Loveridge, J.P., and G. Craye. 1979. Cocoon formation in two species
of Southern African frogs. South Africa J. Sci. 75:13-20.
Loveridge, J.P., and P.C. Withers. 1981. Metabolism and water
balance of active and cocooned African bull frogs Pyxicephalus
adspersus. Physiol. Zool. 54:203-214.
Main, A.R., and P.J. 3entley. 1964. Water relations of Australian
burrowing frogs and tree frogs. Ecology 45:379-332.
Martof, B.S. 1969. Prolonged inanition in Siren lacertina. Copeia
1969:285-239.
McClanahan, L. 1967. Adaptations of the spadefoot toad, Scaphiopus
couchi, to desert environments. Comp. Biochem. Physiol. 20:73-
99.
McClanahan, L., Jr. 1972. Changes in body fluids of burrowed
spadefoot toads as a function of soil water potential. Copeia
1972:209-216.
McClanahan, L., R. Ruibal, and V.H. Shoemaker. 1983. Rate of cocoon
formation and its physiological correlates in a ceratophryd
frog. Physiol. Zool. 56:430-435.
McClanahan, L.L., Jr., V.H. Shoemaker, and R. Ruibal. 1976.
Structure and function of the cocoon of a ceratophryd frog.
Copeia 1976:179-185.
Morton, M.L. 1981. Seasonal changes in total body lipid and liver
weight in the Yoseinite toad. Copeia 1931:234-238.

55
Noble, P.S. 1974. Introduction to biophysical plant physiology.
W.H. Freeman, San Francisco.
Pough, F.H. 1983. Amphibians and reptiles as low-energy systems.
Pages 141-188 _m_ W.P. Aspey and S.I. Lustick, eds. Behavioral
energetics. Ohio State University Press, Columbus, Ohio.
Ray, C. 1958. Vital limits of desiccation in salamanders. Ecology
39:75-83.
Reno, H.W., F.R. Gehlbach, and R.A. Turner. 1972. Skin and
aestivational cocoon of the aquatic amphibian, Siren
intermedia. Copeia 1972:625-631.
Rose, F.L. 1967. Seasonal changes in lipid levels of the salamander
Amphiuma means. Copeia 1967:562-566.
Ruibal, R. 1962. The adaptive value of bladder water in the toad,
Bufo cognatus. Physiol. Zool. 35:213-223.
Ruibal, R., and S.S. Hillman. 1981. Cocoon structure and function in
the burrowing hylid frog, Pternohyla fodiens. J. Herpetology
15:403-408.
Ruibal, R., L. Tevis, Jr., and V. Roig. 1969. The terrestrial
ecology of the spadefoot toad Scaphiopus hammondii. Copeia
1969:571-584.
Seymour, R.S. 1973a. Energy metabolism of dormant spadefoot toads
(Scaphiopus). Copeia 1973:435-446.
Seymour, R.S. 1973b. Gas exchange in spadefoot toads beneath the
ground. Copeia 1973:452-460.
Seymour, R.S. 1973c. Physiological correlates of forced activity and
burrowing in the spadefoot toad, Scaphiopus hammondii. Copeia
1973:103-115.
Shoemaker, V.H., l.L. McClanahan, Or., and R. Ruibal. 1969. Seasonal
changes in body fluids in a field population of spadefoot
toads. Copeia 1969:585-591.
Ultsch, G.R. 1973. Observations on the life history of Siren
lacertina. Herpetologica 29:304-305.
Ultsch, G.R. 1976a. Ecophysiological studies of some metabolic and
respiratory adaptations of sirenid salamanders. Pages 287-312 i£
G.M. Hughes, ed. Respiration of amphibious vertebrates.
Academic Press, London.

56
Ultsch, G.R. 1976b. Respiratory surface area as a factor controlling
the standard rate of Op consumption of aquatic salamanders.
Resp. Physiol. 26:357-369.
van Beurden, E.K. 1980. Energy metabolism of dormant Australian
water-holding frogs (Cyclorana platycephalus). Copeia 1980:787-
799.
Wakeman, J.R, and G.R. Ultsch. 1975. The effects of dissolved Op and
COo on metabolism and gas-exchange partitioning in aquatic
salamanders. Physiol. Zool. 48:348-359.
Withers, P.C. 1977. Measurement of V
J2
water loss with a flow through mask.
123.
J.
, and evaporative
1. Physiol. 42:120-

BIOGRAPHICAL SKETCH
Kay Etheridge was born in Clarksdale, Mississippi, in 1954. She
grew up in Alabama and attended Auburn University where she received
her B.S. in zoology in 1975 and her M.S. in zoology in 1980. Hot yet
satiated with higher education, she migrated still farther south to
the University of Florida where she pursued her Ph.O. During this
pursuit she also worked with manatees and became interested in
tropical biology during a course in Costa Rica. Her primary research
interests involve the physiological ecology of reptiles and
amphibians. Her spare time is devoted largely to the practice of
martial arts and the search for the ultimate chocolate ice cream.
67

I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
^77 <
, . .
Martha L. Crump, Chairman
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
(jJod'h-
r9^
Walter Judd
Associate Professor of Botany
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
A/
: Li , l ,
Harvey B. Lilflywhite
Professor of ¿oology

I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Michelle Wheatly
Assistant Professor of Zoology
This dissertation was submitted to the Graduate Faculty of the
Department of Zoology in the College of Liberal Arts and Sciences and
to the Graduate School and was accepted as partial fulfillment of the
requirements for the degree of Doctor of Philosophy.
December, 1986
Dean, Graduate School

UNIVERSITY OF FLORIDA
3 1262 08554 1448



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