Meeting Abstract
P3.85 Monday, Jan. 6 15:30 Seasonal heterothermy correlates with lower phenotypic flexibility of energetics BORATYNSKI, J.S.*; JEFIMOW, M.; WOJCIECHOWSKI, M.S.; Nicolaus Copernicus Univ., Torun, Poland; Nicolaus Copernicus Univ., Torun, Poland; Nicolaus Copernicus Univ., Torun, Poland jan.boratynski@gmail.com
Heterothermy and phenotypic flexibility enable animals to survive in seasonally changing environments, either by “escaping” from excessive energy expenditure or by adjusting mechanisms of heat production and dissipation. We hypothesized that the capacity for seasonal heterothermy negatively correlates with the scope of this phenotypic flexibility and tested the prediction that adjustments of basal metabolic rate (BMR) in response to short-term changes in ambient temperature (Ta) are greater in summer-acclimated than in winter-acclimated animals that have a broader heterothermic scope. We measured BMR by indirect calorimetry of 40 male Siberian hamsters (Phodopus sungorus) acclimated to winter-like or summer-like conditions for 3 months. After each acclimation period, hamsters were exposed twice for 21 d to different Tas (10, 20 or 28 ° C). We used the difference in BMR measured after the two exposures as an estimate of phenotypic flexibility. Body temperature (Tb) was recorded continuously with implanted data-loggers and body mass (mb) was measured weekly. Variability of Tb was used as a measure of heterothermy. We found that mb in winter-acclimated hamsters was ~22% less than in summer-acclimated ones and, after adjusting for mb, BMR did not differ seasonally (p=0.6). Also, Tb was more variable in winter-acclimated hamsters than summer-acclimated ones (p<0.001). In support of our prediction, we found that BMR in winter-acclimated animals was indeed less flexible than in summer-acclimated hamsters (p=0.02), which suggests that seasonal heterothermy may offer an alternative to extensive adjustments of heat production in heterothermic rodents.
