Postnatal development of thermoregulation in Brandt’s voles Lasiopodomys brandtii
CHI Qing-Sheng~(1, 2), WANG De-Hua~(1**)1. State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, the Chinese Academy of Sciences, Beijing 100080, China2. Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
To understand the characteristics of postnatal development of thermoregulation in Brandt’s voles, the whole developmental story was followed from the birth to 45 days old. Infant body temperatures were measured from the age of day 1 to day 40 immediately after removing the animals from the nest. The resting metabolic rate (RMR) of young voles at 23℃ and 30℃ were measured from day 1 to day 45 using an open circuit respirometry system. Body temperatures were measured before and after the exposure to ambient temperature of 23℃ and 30℃ for 1.5-2 hours during the postnatal development. The homeothermy index and total thermal conductance were also calculated. The effects of huddling on the RMR were investigated. The neonates of Brandt’s voles are typical altricial, born naked with very poor thermoregulatory ability when isolated. Before day 17, voles cannot maintain a constant high body temperature after solitarily exposed to 23℃ for 1.5-2 hours. From day 9 to day 17, the voles increased their thermoregulatory ability rapidly. Young voles started to thermoregulate efficiently on day 17 when the homeothermy index is about 0.97 and no significant difference between body temperatures before and after 23℃ exposure. Although vole pups show characters of poikilotherms during their early lives, the results of RMR measurements indicated that even the newborns can respond to cold by increasing thermogenesis. Huddling among vole pups can decrease their RMR significantly. Although Brandt’s vole pups are relatively weak in heat production and poor in insulation, careful parental care and huddling in the nest can prevent heat loss, thus they can maintain body temperatures at a relatively high constant level (above 33℃) even on day 1, and this can further increase the growth rate.