The physiology of hibernation in common map turtles (Graptemys geographica)

Map turtles from Wisconsin were submerged at 3 degreesC in normoxic and ano xic water to simulate extremes of potential respiratory microenvironments w hile hibernating under ice. In predive turtles, and in turtles submerged fo r up to 150 days, plasma Po-2, Pco(2), pH, [Cl-], [Na+], [K+], total Mg, to tal Ca, lactate, glucose, and osmolality were measured; hematocrit and body mass were determined, and plasma [HCO3-] was calculated. Turtles in anoxic water developed a severe metabolic acidosis, accumulating lactate from a p redive value of 1.7 to 116 mmol/l at 50 days, associated with a fall in pH from 8.010 to 7.128. To buffer lactate increase, total calcium and magnesiu m rose from 3.5 and 2.0 to 25.7 and 7.6 mmol/l, respectively. Plasma [HCO3- ] was titrated from 44.7 to 4.3 mmol/l in turtles in anoxic water. Turtles in normoxic water had only minor disturbances of their acid-base status and ionic statuses; there was a marked increase in hematocrit from 31.1 to 51. 9%. This study and field studies suggest that map turtles have an obligator y requirement for a hibernaculum that provides well-oxygenated water (e.g. rivers and large lakes rather than small ponds and swamps) and that this re quirement is a major factor in determining their micro distribution. (C) 20 01 Elsevier Science Inc. All rights reserved.