The relationship among metabolic rate of tree shrews (Tupaia belangeri) under cold acclimation

Abstract

Many small mammals inhabiting cold environments display enhanced capacity for seasonal changes in nonshivering thermogenesis (NST) and thermoregulatory maximum metabolic rate (MMR). However, it is not known how this plasticity remains in a mammal that rarely experiences extreme cold fluctuations. In order to answer this question, we determined body mass ( Mb), basal metabolic rate (BMR), NST, and MMR on a tree shrews (Tupaia belangeri), acclimated to cold (5 ºC) conditions. NST was measured as the maximum response of metabolic rate (NSTmax) after injection of norepinephrine (NE) in thermoneutrality minus BMR. Maximum metabolic rate was assessed in animals exposed to enhanced heat-loss atmosphere (He-O2) connected with an open-flow respirometer. Body mass and metabolic variables increased significantly after cold acclimation with respect to control group but to a high extent (BMR, 87.97%; NST, 69.77%; and MMR, 32.35%). However, aerobic scope (MMR/BMR), and calculated shivering thermogenesis (ST) did not significantly change with control group. Our data suggest: 1). The body mass and the capacity of heat production in the cold acclimated group were higher; 2). The increase of BMR and MMR during cold acclimation was the main pattern of heat production in the tree shrews.

Keywords

• Cold acclimation
• metabolic rate
• Tupaia belangeri
• thermogenesis plasticity