The physiology of hibernation among painted turtles: The eastern painted turtle Chrysemys picta picta

Eastern painted turtles (Chrysemys picta picta) from Connecticut were subme rged at 3 degrees C in normoxic and anoxic water to simulate potential resp iratory environments within their hibernacula. Those in normoxic water coul d survive submergence for at least 150 d, while those in anoxic water could survive for a maximum of about 125 d. Turtles in normoxic water developed a slight metabolic acidosis as plasma lactate accumulated to about 50 mM in 150 d, while anoxic turtles developed a severe lactic acidosis as plasma l actate reached about 200 mM in 125 d; there was no respiratory acidosis in either group. Plasma [Na+] changed little in either group, [Cl-] fell by ab out one-third in both, and [K+] increased by about fourfold in anoxic turtl es but only slightly in those in normoxic water. Total plasma magnesium and calcium increased profoundly in anoxic turtles but moderately in those in normoxic water. Consideration of charge balance indicates that all major io ns were measured in both groups. Plasma glucose remained unchanged in anoxi c turtles until after about 75 d of submergence, when it increased and cont inued to increase with the duration of anoxia, with much variation among in dividuals; glucose remained unchanged throughout in turtles in normoxic wat er. Hematocrit doubled in 150 d in turtles in normoxic water; in anoxic tur tles, an initial increase was no longer significant by day 100. Plasma osmo lality increased markedly in anoxic turtles, largely because of accumulatio n of lactate, but anoxic turtles only gained about half the mass of turtles in normoxic water, who showed no increase in osmolality. The higher weight gain in the latter group is attributed to selective perfusion and ventilat ion of extrapulmonary gas exchange surfaces, resulting in a greater osmotic influx of water. The physiologic responses to simulated hibernation of C. picta picta are intermediate between those of Chrysemys picta bellii and Ch rysemys picta dorsalis, which correlates with the severity of the winter ea ch subspecies would be expected to encounter.