Seasonal changes in the thermoregulation of laboratory golden hamsters during acclimation to seminatural outdoor conditions.
Proper adjustments of the thermoregulatory mechanisms ensure survival in the natural environment. In the present study, we tested the hypothesis that laboratory golden hamsters (Mesocricetus auratus) housed under seminatural outdoor conditions are able to acclimatize to daily and seasonal changes in the environment despite their long history of breeding in captivity. The animals experienced natural changes in the photoperiod and ambient temperature characteristic for central Poland. During experiments in the thermal gradient system, the daily rhythms of body temperature (measured as the temperature of brown adipose tissue, TBAT), preferred ambient temperature (PTa) and activity were measured in summer, autumn and spring. We found that mean TBAT was highest in autumn and least in summer, reflecting seasonal changes in the capacity for nonshivering thermogenesis (NST). In summer, TBAT followed the robust daily rhythm with the amplitude of 1.1+/-0.1 degrees C. This amplitude was depressed in autumn (0.2+/-0.1 degrees C) and partially restored in spring (0.4+/-0.1 degrees C). Seasonal changes in the daily amplitude of TBAT recorded during both transitional periods, i.e., in autumn and spring, seem to be associated with hamsters' hibernation. In autumn, mean daily PTa was lower than in summer and spring, indicating the lowering of a set point for core body temperature (Tb) regulation. Locomotor activity was much higher in spring than in summer and autumn, and it always predominated at night. We conclude that laboratory golden hamsters housed under seminatural conditions express daily and seasonal changes in the thermoregulatory mechanisms that, despite long history of breeding in captivity, enable proper acclimatization to seasonally changing environment and ensure successful hibernation and winter survival.
Jefimow
Małgorzata
M
Department of Animal Physiology, Institute of General and Molecular Biology, Nicholas Copernicus University, ul. Gagarina 9, PL 87-100 Toruń, Poland. jefimow@biol.uni.torun.pl
Wojciechowski
Michał
M
Tegowska
Eugenia
E
D000222:Adaptation, Physiological; D000818:Animals; D001833:Body Temperature Regulation; D001835:Body Weight; D006224:Cricetinae; D003624:Darkness; D008027:Light; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity; D012621:Seasons