Meeting Abstract
S10.5 Friday, Jan. 7 The effects of diet on thermoregulation and torpor in Siberian hamsters. GUTOWSKI, Jakub P.*; DUBICKI, Adam; WOJCIECHOWSKI, Michal S.; JEFIMOW, Malgorzata; Nicolaus Copernicus Univ, Torun, Poland; Nicolaus Copernicus Univ, Torun, Poland; Nicolaus Copernicus Univ, Torun, Poland; Nicolaus Copernicus Univ, Torun, Poland gutowski@doktorant.umk.pl
Body fat and its composition influence the physiology of heterothermic mammals during winter torpor. We tested the hypothesis that thermoregulation and torpor characteristics in Siberian hamsters (Phodopus sungorus) depend on the composition of their diet. We used 24 male hamsters kept under semi-natural conditions of central Poland. From May to September 2009 all animals were initially fed standard rodent pellets, mealworms, sunflower and flax seeds. They were then divided into two diet groups – one supplemented only with mealworms and the other flax and sunflower seeds. In autumn (September) and winter (January) we determined basal metabolic rate (BMR), lower critical temperature (TLC) and non-shivering thermogenesis (NST) capacity. Body temperature (Tb) was measured continuously with miniature temperature loggers. Animals were weighed once a month. In autumn, BMR averaged 7.60±1.47 mWg-1 (mean±SD), TLC was 25.7±1.6°C and mean body mass (mb) was 49.1±6.0g. In winter BMR (8.88±0.74mWg-1), TLC (23.2±1.7°C) and mb (37.8±5.66g) were independent of diet in both diet groups. There was also no difference in NST capacity between both diet groups (mean 1.61±0.19W). Metabolic rate below TLC was lower in hamsters supplemented with seeds (p<0.05), but the slopes of regression lines below TLC were similar in both diet groups. The mean torpor Tb was higher in hamsters with supplementary seeds than in hamsters fed mealworms (29.1±1.8°C and 25.2±3.4°C, p<0.05). The results indicate that dietary supplementation with seeds has no effect on hamster thermoregulation at thermoneutral temperature, but results in lower metabolic rate below TLC and in shallower daily torpor. Both might result from higher fat insulation in seed-fed hamsters.
