Meeting Abstract

P3.205  Tuesday, Jan. 6  Energy metabolism, body temperature and non-shivering thermogenesis in bats acclimating to simulated winter conditions. GUTOWSKI, J.; WOJCIECHOWSKI, M.S.*; Nicolaus Copernicus University, Torun, Poland; Nicolaus Copernicus University, Torun, Poland mwojc@umk.pl

To test the predictions that 1) bats decrease their lower critical temperature (T_lc) in response to seasonal changes in ambient conditions, and 2) that winter-acclimated bats increase their capacity for non-shivering thermogenesis (NST), we measured metabolic rate (MR), body temperature (T_b) and NST in 6 Myotis myotis during acclimation to simulated changes in ambient conditions. MR (VO₂ by indirect calorimetry) and T_b were measured simultaneously at ambient temperatures (T_a) between 5 °C and 38 °C. Capacity for NST was measured at T_a=20±2 °C following injection of noradrenaline (NA). The same individuals were tested in autumn, winter and spring. In autumn and spring, bats were housed indoors, in flight cages and fed daily ad libitum; the photoperiod was natural. In winter, bats hibernated in an artificial hibernaculum and were fed every five days. The bats’ resting MR did not change with season (F(2,16)=1.63, p>0.05, 7.21±0.80 mWg^-1). However, mean euthermic T_b decreased from ~36.6 °C and ~37.0 °C, in autumn and spring, to ~36.1 °C in winter (F(2,66)=4.51, p<0.05). This resulted in winter T_lc dropping by ~4 °C and ~2 °C compared to autumn and spring, respectively. VO₂ following NA did not change, but maximum T_b was higher after NA injection in winter and in spring than in autumn (F(2,20)=4.81, p<0.05). Our data suggest that in winter M. myotis saves energy by lowering its euthermic T_b. Higher maximum T_b following NA injection indicates increasingly effective use of NST. The changes also indicate frugal energy expenditure during intra-hibernation euthermic episodes.