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HERPETOLOGICAL NOTES 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 in- fluences 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 pres- sure 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 in- fluence in the reptilian central circulation. Support for this view lies in the fact that when the bulbus cordis contracts, it is ob- served 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 pul- monary resistance in the crocodilian heart is in the pulmonary outflow tract.

Since the pulmonary circuit possesses con- siderable volumetric compliance, the bulbus cordis in the squamate heart likely does not function to prevent overloading of the pul- monary 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 ven- tricular ejection phase. To contract after ventricular systole would be an hemody- namically 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 sup- ported, in part, through contract AT(29-1)- 1183 between the U.S. Atomic Energy Com- mission 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.

LITERATURE CITED

BRADY, A. J. 1964. Physiology of the amphibian heart, p. 211-250. In: Physiology of the Am-

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 in- fluences 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 pres- sure 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 in- fluence in the reptilian central circulation. Support for this view lies in the fact that when the bulbus cordis contracts, it is ob- served 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 pul- monary resistance in the crocodilian heart is in the pulmonary outflow tract.

Since the pulmonary circuit possesses con- siderable volumetric compliance, the bulbus cordis in the squamate heart likely does not function to prevent overloading of the pul- monary 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 ven- tricular ejection phase. To contract after ventricular systole would be an hemody- namically 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 sup- ported, in part, through contract AT(29-1)- 1183 between the U.S. Atomic Energy Com- mission 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.

LITERATURE CITED

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.

FURMAN, K. I. 1960. The electrocardiogram of 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.

GROSS, D. 1955. The auricular T wave and its 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. Electrocardiographic investiga- tion of the heart of fish. Expl. Med. Surg. 6:31-62.

MARCH, H. W. 1961. Persistence of a functioning bulbus cordis homologue in the turtle heart. Amer. J. Physiol. 201:1109-1112.

MULLEN, R. K. 1967. Comparative electrocardiog- raphy of the Squamata. Physiol. Zool. 40:114- 126.

SATCHELL, G. H. 1971. Circulation in fishes. Cambridge Univ. Press, London.

STEGGERDA, F. R. AND H. E. ESSEX. 1957. Circu- lation and blood pressure in the great vessels and heart of the turtle (Chelydra serpentina). Amer. J. Physiol. 190:310-326.

VALENTINUZZI, M. E. 1969. Observations on the 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.

ZUCKERMAN, R. 1957. Grundriss und Atlas der Elektrokardiographie. Thieme. Leipzig.

ROBERT K. MULLEN EGIG, Inc., Goleta, California 93017.

THERMAL ACCLIMATION AND TOL- ERANCE IN THE HFI T.BENDER, CRYP- TOBRANCHUS ALLEGANIENSIS.-Criti- cal thermal maxima (CTM), the temperature at which animals lose their organized loco- motory 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; Hutchi- son, 1961; Spotila, 1972). However, no ex- perimental studies have been made on the thermal acclimation or tolerances of the North American giant salamanders Am- phiuma, Cryptobranchus, Necturus and Siren. Anecdotal accounts of the temperature tol- erance of Cryptobranchus were given by Frear (1882), Townsend (1882), Reese (1906),

phibia. J. A. Moore, Ed. Academic Press, New York.

FURMAN, K. I. 1960. The electrocardiogram of 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.

GROSS, D. 1955. The auricular T wave and its 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. Electrocardiographic investiga- tion of the heart of fish. Expl. Med. Surg. 6:31-62.

MARCH, H. W. 1961. Persistence of a functioning bulbus cordis homologue in the turtle heart. Amer. J. Physiol. 201:1109-1112.

MULLEN, R. K. 1967. Comparative electrocardiog- raphy of the Squamata. Physiol. Zool. 40:114- 126.

SATCHELL, G. H. 1971. Circulation in fishes. Cambridge Univ. Press, London.

STEGGERDA, F. R. AND H. E. ESSEX. 1957. Circu- lation and blood pressure in the great vessels and heart of the turtle (Chelydra serpentina). Amer. J. Physiol. 190:310-326.

VALENTINUZZI, M. E. 1969. Observations on the 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.

ZUCKERMAN, R. 1957. Grundriss und Atlas der Elektrokardiographie. Thieme. Leipzig.

ROBERT K. MULLEN EGIG, Inc., Goleta, California 93017.

THERMAL ACCLIMATION AND TOL- ERANCE IN THE HFI T.BENDER, CRYP- TOBRANCHUS ALLEGANIENSIS.-Criti- cal thermal maxima (CTM), the temperature at which animals lose their organized loco- motory 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; Hutchi- son, 1961; Spotila, 1972). However, no ex- perimental studies have been made on the thermal acclimation or tolerances of the North American giant salamanders Am- phiuma, Cryptobranchus, Necturus and Siren. Anecdotal accounts of the temperature tol- erance of Cryptobranchus were given by Frear (1882), Townsend (1882), Reese (1906),

805 805

COPEIA, 1973, NO. 4

o 35- \ x \

_ 334- 3 _ .

33- ,0 \-_

0 2 4 6 8 10 12 14 O 2 4 6 8 10 12 14

DAYS Fig. 1. Rate of acclimation in Cryptobranchus alleganiensis bishopi when transferred from two

or more weeks of acclimation at 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). Nicl (1973) mentioned that he at 20-22 C could withstanc to ice water near 1 C an water for at least three da

Max A. Nickerson provi4 sample of live C. allegan lected on 24 and 25 Sept( North Fork of the White Missouri. The animals w vironmental rooms and ( and 25 ? 1 C and were throughout the acclimatic to six weeks. Critical thei

I I I I

I I? _95 (9)

31 32 33 34 CT Max ?C

Fig. 2. Critical thermal n Cryptobranchus alleganiensis to 5, 15 and 25 C. The mea long vertical lines, the range lines bounded by short vert dard deviation on each sid hollow rectangles and two each side of the mean by solik size is in parentheses.

kerson and Mays determined by the method of Hutchison llbenders collected (1961), where the onset of spasms was I a sudden transfer taken as the endpoint and was marked d shipment in ice by a twitching of the limbs and trunk, gaping Lys. of the mouth and tetany of the hyoidal mus- ded us with a large culature. The loss of righting response was iensis bishopi col- measured, but found to be highly variable ember 1972 in the and inaccurate; the loss of righting response River, Ozark Co., ranged from 0.5 C to 2.6 C lower than the

rere placed in en- CTM. All measurements were made between chambers at 5, 15 1900 and 2130 hrs to avoid differences due * fed live crayfish to possible daily rhythms in CTM (Mahoney mn periods of two and Hutchison, 1969). No significant dif- rmal maxima were ferences in CTM were noted between sexes.

Body size (29-644 g) also had no apparent effect on the CTM.

l , I ' l , Acclimation rates were determined for animals acclimated to 5 C for at least two

25? (10)1 1 - _L. I weeks, transferred to 25 C, and the CTM determined on different samples until a new

5?(10) stabilized level of tolerance was attained. The rate of acclimation from 25 to 5 C was )determined in the same manner. The ac- climation from 5 to 25 C required approxi-

1 ,l l , l l mately 4 days, while the reverse change of 35 36 37 25 to 5 C necessitated about twice the time

for complete acclimation (Fig. 1). The slower naxima (CTMax) of rate of acclimation to lower temperatures is ; bishopi acclimated commonly known for lower vertebrates (Fry, in is represented by but the rate of acclimation for -by long horizontal by long horizontal 1967), but the rate of acclimation for C. a. :ical lines, one stan- bishopi appears to be slower than for any le of the mean by amphibian previously studied in approxi- iSretdanrlerrrs mpe mately the same range of temperatures. Most

species acclimate to 23-30 C after transfer

806

HERPETOLOGICAL NOTES

from 5-6 within 3 days or less while ac- climation 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 dif- ference 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 bis- lineata wilderae, Desmognathus monticola, D. quadramaculatus (Hutchison, 1961), Des- mognathus fuscus and Plethodon dorsalis (Spotila, 1972), all from cool mountain hab- itats, 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 rela- tively 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 rela- tively 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

both suggested this study and provided the animals.

LITERATURE CITED

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 al- titude. Comp. Biochem. Physiol. 24:93-111.

. 1970. Amphibia, 135-166. In: Compara- tive 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. Cryptobranchus alleganiensis in West Virginia. Proc. West Virginia Acad. Sci. 7:28-30.

HUTCHISON, V. H. 1961. Critical thermal maxima 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. Hell- benders: North American giant salamanders. Milwaukee Public Museum Scientific Series, in press.

REESE, A. M. 1906. Observations on the reac- tions of Cryptobranchus and Necturus to light and heat. Biol. Bull. 11:93-99.

SPOTILA, J. R. 1972. Role of temperature and water in the ecology of lungless salamanders. Ecol. Monogr. 42:95-125.

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.

807