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805
HERPETOLOGICAL NOTES
pared to that of fishes and amphibians, and
serves an entirely different function than it
does in these latter groups.
ECG's seem to indicate that the bulbus
cordis in squamate reptiles does not react
primarily to transmitted depolarization influences from other parts of the heart. The
behavior of the bulbus suggests that its
primary contraction stimulus may arise from
pulmonary filling pressure. Since this pressure will depend upon a variable pulmonary
circuit compliance, the bulbus may not be
expected to contract in absolute synchrony
with the ventricle. If the bulbus cordis does
react to pulmonary filling pressure, this
structure may then act as a differential flow
regulator and, as such, is an homeostatic influence in the reptilian central circulation.
Support for this view lies in the fact that
when the bulbus cordis contracts, it is observed to obstruct the pulmonary outflow
tract of the chelonian heart (Woodbury and
Robertson, 1942; March, 1961). White (1969)
has also demonstrated that the site of pulmonary resistance in the crocodilian heart
is in the pulmonary outflow tract.
Since the pulmonary circuit possesses considerable volumetric compliance, the bulbus
cordis in the squamate heart likely does not
function to prevent overloading of the pulmonary circulation, but permits adequate
filling of the systemic circulation. However
one interprets the end function of the bulbus
cordis, experimental evidence leaves little
question that it does function to moderate
a left-to-right shunt. To so function, the
bulbus cordis must contract during the ventricular ejection phase. To contract after
ventricular systole would be an hemodynamically neutral event. Thus, if bulbus
cordis activity is to be seen in the limb lead
ECG of reptiles, the recorded event will
be quite proximal to, or superimposed upon,
the ventricular QRS.
Acknowledgments.-This research was supported, in part, through contract AT(29-1)1183 between the U.S. Atomic Energy Commission and EG8cG, Inc., and Public Health
Service, National Institutes of Health Grants
H-7014 and HE07014-01S1, James A. Peters,
Principal Investigator, to whose memory this
paper is dedicated.
LITERATURECITED
BRADY,A. J. 1964. Physiology of the amphibian
heart, p. 211-250. In: Physiology of the Am-
phibia. J. A. Moore, Ed. Academic Press,
New York.
K. I. 1960. The electrocardiogramof
FURMAN,
the south african clawed toad (Xenopus laevis)
with special reference to temperature effects.
S. Afr. J. Med. Sci. 25:109-118.
GREIL,A. 1903. Beitrage zur vergleichenden
Anatomie und Entwicklungsgeschichte des
Herzen und des Truncus arteriosus der
Wirbelthiere. Morph. Jahrb. 31:123-310.
D. 1955. The auricular T wave and its
GROSS,
correlation to the cardiac rate and to the
P wave. Amer. Heart J. 50:24-73.
JOHANSEN,K. 1965. Cardiovascular dynamics
in fishes, amphibians, and reptiles. Ann. N.
Y. Acad. Sci. 127:414-442.
KISCH,B. 1948. Electrocardiographicinvestigation of the heart of fish. Expl. Med. Surg.
6:31-62.
H. W. 1961. Persistenceof a functioning
MARCH,
bulbus cordis homologue in the turtle heart.
Amer. J. Physiol. 201:1109-1112.
MULLEN,R. K. 1967. Comparativeelectrocardiography of the Squamata. Physiol. Zool. 40:114126.
G. H. 1971. Circulation in fishes.
SATCHELL,
CambridgeUniv. Press,London.
F. R. ANDH. E. ESSEX. 1957. CircuSTEGGERDA,
lation and blood pressure in the great vessels
and heart of the turtle (Chelydra serpentina).
Amer. J. Physiol. 190:310-326.
M. E. 1969. Observations on the
VALENTINUZZI,
electrical activity of the snake heart. J.
Electrocardiol. 2:39-50.
WHITE,F. N. 1968. Functional anatomy of the
heart of reptiles. Amer. Zoologist. 8:211-219.
. 1969. Redistribution of cardiac output
in the diving alligator. Copeia 1969:567-570.
R. 1957. Grundrissund Atlas der
ZUCKERMAN,
Elektrokardiographie.Thieme. Leipzig.
ROBERT K. MULLEN EGIG,
Inc., Goleta,
California 93017.
THERMAL ACCLIMATION AND TOLERANCE IN THE HFI T.BENDER, CRYPTOBRANCHUS ALLEGANIENSIS.-Critical thermal maxima (CTM), the temperature
at which animals lose their organized locomotory ability and are unable to escape from
conditions that would promptly lead to their
death (Cowles and Bogert, 1944), of North
American amphibians have been widely
studied (Brattstrom, 1963, 1968, 1970; Hutchison, 1961; Spotila, 1972). However, no experimental studies have been made on the
thermal acclimation or tolerances of the
North American giant salamanders Amphiuma, Cryptobranchus, Necturus and Siren.
Anecdotal accounts of the temperature tolerance of Cryptobranchus were given by
Frear (1882), Townsend (1882), Reese (1906),
COPEIA, 1973, NO. 4
806
o
35-
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x
\
_
3
_ 334-
.
33-
,0
0
O
2
2
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6
4
4
8
6
8
10
10
12
14
12
14
DAYS
Fig. 1. Rate of acclimation in Cryptobranchusalleganiensis bishopi when transferredfrom two
or more weeks of acclimationat 5 to 25 C, and from 25 to 5 C. Each point represents the mean
critical thermal maximum (CTMax) for three to five animals.
and Green (1933). Niclkerson and Mays
(1973) mentioned that he llbenders collected
at 20-22 C could withstancI a sudden transfer
to ice water near 1 C and shipment in ice
water for at least three daLys.
Max A. Nickerson provi4ded us with a large
sample of live C. allegan iensis bishopi collected on 24 and 25 Sept(ember 1972 in the
North Fork of the White River, Ozark Co.,
Missouri. The animals wrere placed in environmental rooms and (chambers at 5, 15
and 25 ? 1 C and were* fed live crayfish
throughout the acclimaticmn periods of two
to six weeks. Critical theirmal maxima were
l ,I
'
25? (10)1 1 _L.
determined by the method of Hutchison
(1961), where the onset of spasms was
taken as the endpoint and was marked
by a twitching of the limbs and trunk, gaping
of the mouth and tetany of the hyoidal musculature. The loss of righting response was
measured, but found to be highly variable
and inaccurate; the loss of righting response
ranged from 0.5 C to 2.6 C lower than the
CTM. All measurements were made between
1900 and 2130 hrs to avoid differences due
to possible daily rhythms in CTM (Mahoney
and Hutchison, 1969). No significant differences in CTM were noted between sexes.
Body size (29-644 g) also had no apparent
effect on the CTM.
,
l
-
I
Acclimation
rates
were
determined
for
animals acclimated to 5 C for at least two
weeks, transferred
to 25 C, and the CTM
determined on different samples until a new
I
I
I
I
5?(10)
stabilized level of tolerance was attained.
The rate of acclimation from 25 to 5 C was
I _95
I?
(9)
)determined in the same manner. The acclimation from 5 to 25 C required approxil ,l
1 ,l l
mately 4 days, while the reverse change of
31
32
33
34
35
36
37
25 to 5 C necessitated about twice the time
CT Max ?C
for complete acclimation (Fig. 1). The slower
Fig. 2. Critical thermal nnaxima (CTMax) of rate of acclimation to lower temperatures is
Cryptobranchus alleganiensis ; bishopi acclimated commonly known for lower vertebrates (Fry,
to 5, 15 and 25 C. The meain is representedby
but the rate of acclimation for
long vertical lines, the range-by
by long horizontal 1967), but the rate of acclimation for C. a.
lines bounded by short vert:ical lines, one stan- bishopi appears to be slower than for any
dard deviation on each sidle of the mean by amphibian previously studied in approxihollow rectangles and two
mately the same range of temperatures. Most
each side of the mean by solikiSretdanrlerrrsmpe
size is in parentheses.
species acclimate to 23-30 C after transfer
HERPETOLOGICAL NOTES
from 5-6 within 3 days or less while acclimation in the opposite direction requires
less than 100 hrs (Brattstrom, 1968). Aquatic
adults of Notophthalmus viridescens required
only four days to acclimate from 20 to 4 C
and two days, from 4 to 20 C (Hutchison,
1961).
The mean CTM of the Ozark hellbenders
were 32.70 ? 0.37 C at 5 C acclimation,
32.99 ? 0.40 C at 15 C, and 36.57 ? 0.46
C at 25 C (Fig. 2). The difference between
animals acclimated to 5 and 15 C was not
significant (t = 0.534, p > .5), but the difference between animals acclimated to 15
and 25 C was highly significant (t = 8.413,
p < .001). The CTM of C. a. bishopi is
low compared to that of other salamanders
previously studied at similar acclimation
temperatures; only Rhyacotriton olympicus
(Brattstrom, 1963), juvenile Eurycea bislineata wilderae, Desmognathus monticola, D.
quadramaculatus (Hutchison, 1961), Desmognathus fuscus and Plethodon dorsalis
(Spotila, 1972), all from cool mountain habitats, appear to have a similar or lower CTM.
The rate of acclimation to both low and
high temperatures, however, is appreciably
slower than that of any amphibian previously
studied.
Cryptobranchus a. bishopi inhabits relatively cool and larger streams of the Black
River system and the North Fork of White
River in southeastern Missouri and adjacent
Arkansas. The water temperature measured
over a period of 15 months at the collection
site of the animals used in this study varied
between 9.8 C in February and 22.5 C in
July (Nickerson and Mays, 1972). The relatively low CTM and the slow rate of thermal
acclimation in this species may be a result
of its evolution in a relatively cool and stable
aquatic environment.
We are grateful to M. A. Nickerson, who
807
both suggested this study and provided the
animals.
LITERATURECITED
BRATTSTROM,B.
H. 1963. A preliminary review
of the thermal requirements of amphibians.
Ecology 44:238-255.
. 1968. Thermal acclimation in anuran
amphibians as a function of latitude and altitude. Comp. Biochem. Physiol. 24:93-111.
. 1970. Amphibia, 135-166. In: Comparative Physiology of Thermoregulation. Vol. 1:
Invertebrates and Nonmammalian Vertebrates.
Whittow, C. G. (ed.) Academic Press, New
York.
COWLES, R. B., AND C. M. BOGERT. 1944. A
preliminary study of the thermal requirements
of desert reptiles. Bull. Mus. Nat. Hist. 83:
265-296.
FREAR,W. 1882. Vitality of the mud puppy.
Amer. Nat. 16:325-326.
FRY, F. E. J. 1967. Responses of vertebrate
poikilotherms to temperature, 375-409. In:
Thermobiology. Rose, A. H. (ed.) Academic
Press, New York.
GREEN,N. B. 1933. Cryptobranchusalleganiensis
in West Virginia. Proc. West Virginia Acad.
Sci. 7:28-30.
V. H. 1961. Critical thermal maxima
HUTCHISON,
in salamanders. Physiol. Zool. 34:92-125.
MAHONEY, J. J., AND V. H.
HUTCHISON. 1969.
Photoperiod acclimation and 24-hour variation
in the critical thermal maxima of a tropical
and temperate frog. Oecologia 2:143-161.
NICKERSON,M. A., AND C. E. MAYS. 1973. Hellbenders: North American giant salamanders.
Milwaukee Public Museum Scientific Series,
in press.
REESE,A. M. 1906. Observations on the reac-
tions of Cryptobranchusand Necturus to light
and heat. Biol. Bull. 11:93-99.
1972. Role of temperature and
water in the ecology of lungless salamanders.
Ecol. Monogr. 42:95-125.
SPOTILA, J. R.
TOWNSEND, C.
H. 1882. Habits of Menopoma.
Amer. Nat. 16:139-140.
VICTOR H. HUTCHISON, GUSTAV ENGBRETSON
AND DOUGLAS TURNEY,
Department of
Zoology, University of Oklahoma, Norman,
Oklahoma 73069.