AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 3 530-R537, Copyright © 1992 by American Physiological Society

ARTICLES

Natural freezing survival by painted turtles Chrysemys picta marginata and C. picta bellii

T. A. Churchill and K. B. Storey
Department of Biology, Carleton University, Ottawa, Ontario, Canada.

Hatchlings of both the Midland (Chrysemys picta marginata) and Western (C. picta bellii) subspecies of the painted turtle tolerate the freezing of extracellular body fluids while overwintering in terrestrial nests. Fall-collected hatchlings survived 3 days of continuous freezing at -2.5 degrees C, with ice contents of 43.5 +/- 1.0% of total body water (SE; n = 24) for C. picta marginata and 46.5 +/- 0.8% (n = 32) for C. picta bellii. Survival times dropped to 4-5 h when temperature was lowered to -4 degrees C, correlated with ice contents of greater than or equal to 50%. However, C. picta marginata tested immediately after excavation from nests in the spring showed greater freeze tolerance, with survival extending to 11 days at -2.5 degrees C and a higher mean ice content of 50.2 +/- 1.2% (n = 6). Spring hatchlings also had high supercooling points, -1.07 +/- 0.13 degrees C (n = 8), that dropped within 3 days to -4.83 +/- 0.83 degrees C (n = 4), suggesting a breakdown of endogenous ice-nucleating agents when hibernation ended. A search for possible cryoprotectants showed that both subspecies accumulated glucose and lactate in liver during freezing (net increase = 3-13 mumols/g wet wt); both also maintained large free amino acid pools in organs, with taurine making up 21-47% of the total.

This article has been cited by other articles:

				J. P. Costanzo, P. J. Baker, S. A. Dinkelacker, and R. E. Lee Jr Endogenous and exogenous ice-nucleating agents constrain supercooling in the hatchling painted turtle J. Exp. Biol., February 1, 2003; 206(3): 477 - 485. [Abstract] [Full Text] [PDF]