P1.219 Wednesday, Jan. 4 Seasonal dynamics and influence of hibernaculum temperature on energy reserves in the wood frog, Rana sylvatica COSTANZO, J.P.*; DO AMARAL, M.C.; ROSENDALE, A.R.; LEE, R.E.; Miami Univ., Oxford firstname.lastname@example.org
The wood frog (Rana sylvatica), a terrestrial species that ranges to the Arctic Circle, overwinters beneath forest duff where it encounters subzero temperatures. Frogs may hibernate for >6 mo, during which time they do not feed and energy reserves are used to meet metabolic demands. We monitored seasonal dynamics of nutrient storage and consumption to determine the relative importance of lipid, carbohydrate, and protein in their overwintering energy budget. We also examined the influence of ambient temperature on energy consumption. Fat bodies, which were heaviest in summer frogs, were reduced in mass by 50% during the pre-hibernal period and fully expended between October and April. In contrast, the liver glycogen reserve (as well as dry liver mass) was sustained throughout the winter, but then decreased 75% by April, after frogs had aroused from hibernation. Glycogen sparing in winter supports the freezing adaptation in which glucose, a cryoprotectant, is copiously mobilized in response to ice nucleation. Marked reductions in dry masses of the carcass (20%) and gastrocnemius (25%) between November and January indicated that protein was also utilized in winter, but not in autumn. Frogs exposed to 4°C or 0°C in simulated hibernation survived from early November until early March (120 d), but half the frogs kept at 10°C died. Frogs in the 10°C group lost 18% of their initial body mass and had relatively small livers and fat bodies, and lower carcass and gastrocnemius masses. Frogs kept at 4°C or 0°C gained mass (from water retention) and consumed much less energy, suggesting that low temperatures are critical to successful hibernation in R. sylvatica. Supported in part by NSF IOS1022788.