The physiology of hibernation among painted turtles: the midland painted turtle (Chrysemys picta marginata)

Midland painted turtles from Michigan were submerged at 3 degreesC in normo xic and anoxic water. In predive, and in turtles submerged for up to 150 da ys, plasma PO2, PCO2, pH, [Cl-], [Na+], [K+], total Mg, total Ca, lactate, glucose, and osmolality were measured; hematocrit and mass were determined, and plasma [HCO3-] was calculated. Anoxic turtles developed a severe metab olic acidosis, accumulating lactate from a predive value of 4.4 mmol/L to a 150-day value of 185 mmol/L, associated with a fall in pH from 7.983 to 7. 189. To buffer lactate increase, total calcium and magnesium rose from 3.7 and 2.6 to 58.9 and 11.8 mmol/L, respectively. Plasma [HCO3-] was titrated from 39.2 to 4.8 mmol/L in anoxic turtles. Turtles in normoxic water had on ly minor disturbances of their acid-base and ionic statuses, associated wit h a much smaller increase of lactate to 23 mmol/L; there was a marked incre ase in hematocrit from 29.1% to 42.1%. We suggest that it is ecologic, rath er than phylogenetic, relationships that determine the responses of painted turtles to prolonged submergence associated with hibernation. (C) 2000 Els evier Science B.V. All rights reserved.