DISHONG, B.D.*; MUIR, T.J.; COSTANZO, J.P.; LEE JR., R.E.; Miami Univ., Oxford, OH; Miami Univ., Oxford, OH; Miami Univ., Oxford, OH; Miami Univ., Oxford, OH: Influence of Temperature on Overwintering Energetics in the Hatchling Painted Turtle, Chrysemys picta
Painted turtles (Chrysemys picta) hatch in late summer but usually remain inside their nests until emerging in spring. During this 8-mo period, the hatchlings are aphagic and rely upon somatic energy reserves to meet their metabolic demands. Due to the shallowness of their nests (5-10 cm below ground), ambient temperature can vary widely, with potentially significant consequences for the energetics and survival of the enclosed turtles. Our aim in this study was to investigate thermal effects on winter energy consumption, metabolism, and survival in hatchling painted turtles. Groups of hatchlings (n = 8) were kept in simulated hibernation and exposed to 15�, 10�, or 4�C for 194 d. At the end of simulated hibernation, turtles kept at 4�C appeared healthy, while those held at 10� and 15�C appeared physically debilitated. Turtles kept at 4�C lost only 5.3% of their initial body mass, whereas significantly more mass was lost by the turtles kept at 10�C (13.4%) and 15�C (16.0%). At the end of hibernation, the liver and internalized yolk sac, which contain the major energy stores in hatchling turtles, jointly comprised a larger percentage of the carcass mass in the 4�C group (7.3%) as compared to the 10� and 15�C groups (5.7% and 4.9%, respectively). Closed-system respirometry experiments, conducted in mid-winter, showed that the rate of oxygen consumption in the 4�C group (1.1 �l/g/h) was more than an order of magnitude lower (Q10 = 10.5) than that measured in the 15�C group (12.6 �l/g/h). Low environmental temperatures enable overwintering hatchling turtles to conserve their finite energy reserves, which are needed to survive lengthy aphagia within the nest and to fuel post-emergence activities. Funded by the Arnold and Mabel Beckman Foundation (B.D.D.) and the NSF IOB 0416750 (J.P.C.)
