OUFIERO, C.E.*; ANGILLETTA, M.J.; Indiana State Univ., Terre Haute: Embryo Energetics and Thermal Acclimation at Fluctuating Temperatures

Variation in incubation temperature may cause differences in metabolic rate at the embryonic stage, which may also persist in juveniles. Previous studies of reptiles have documented effects of constant incubation temperatures on the energetics of embryos and the thermal acclimation of metabolic rate during embryonic development. However, embryos do not experience constant temperature during incubation in nature. The metabolism of lizard embryos of the eastern fence lizard (Sceloporus undulatus) was measured under cycles of temperature. We also compared the metabolic rates of hatchling from these treatments to determine whether different cycles of temperature induced thermal acclimation of metabolic rate. Eggs were incubated at diel cycles of 20-30 C and 20-34 C, which mimick temperatures of natural nests. Every four days, closed-system respirometry was used to record both oxygen consumption and carbon dioxide production of embryos from each treatment during a complete 24 h cycle. Measuring metabolic rates of embryos throughout the incubation period enabled us to calculate the energy invested in maintenance and the metabolic cost of growth under the two thermal regimes. As hatchlings emerged, they were maintained under identical environmental conditions. After their first feeding and defecation, metabolic rates of hatchlings at 33 C were measured using closed system respirometry. Two measurements were taken on separate days for each individual and the lowest was considered to be an estimate of resting metabolic rate. These data enabled us to determine whether incubation temperature has long-term effects on the energetics of individuals. The results of this study will be compared to those of studies of embryonic metabolism and thermal acclimation under constant incubation temperatures.