COSTANZO, J.P.; JONES, E.J.*; LEE, R.E.: Physiological Responses to Supercooling and Anoxia in the Hatchling Painted Turtle

We investigated physiological responses to supercooling in hatchling painted turtles (Chrysemys picta), which remain in their natal nests over winter. These turtles are freeze tolerant, but also rely on supercooling to survive exposure to the lower temperatures occurring in nests during winter. We measured whole-body concentrations of lactate, glucose, glycerol, and ATP in turtles chilled for 5 days at 0, -4, or -6 degrees C, or chilled for 19 days at -6 degrees C. In a companion experiment we measured metabolite concentrations in turtles exposed for 1, 4, or 8 days to an anoxic environment. Chilling and anoxia exposure both resulted in an increase in concentrations of lactate and glucose, a decrease in the glycerol concentration, and no change in the ATP pool, suggesting that oxygen delivery and/or utilization is impaired in supercooled turtles. Anoxia tolerance may be an important preadaptation for surviving exposure to subzero temperatures in hatchling C. picta.