Role of body temperature in seasonal acclimatization: Photoperiod‐induced rhythms and heat production in Meriones crassus

Heat production by means of nonshivering thermogenesis (NST) and food consumption were compared in individuals of the fat jird Meriones crassus , acclimated to 8L:16D and 16L:8D cycles at an ambient temperature of 28°C. Daily rhythms of body temperature were compared at the same time. A significant ( P < 0.05 and P < 0.005) increase in NST and food consumption was noted in fat jirds acclimated to short photoperiod 8L:16D when compared with those acclimated to a long photoperiod 16L:8D. A clear difference in rhythms of body temperature was observed between the two groups. In light of these results it is reasonable to assume that seasonal acclimatization in the fat jird can be partly induced by the change of photoperiod. Rhythms of body temperature in the fat jird are entrained by photoperiod and appear to be adjusted to the different metabolic demands of summer and winter.