Cold-Acclimation in the Marsupial Antechinus-Stuartii - Thyroid-Function and Metabolic-Rate

Abstract

Metabolic rate and food energy intake of Antechinus stuartii at 5°C and 25°C, and thyroid iodine secretion rate of A. stuartii and Mus musculus were compared after acclimation to 5°C or 25°C for 6-8 weeks. Acclimation to cold increased minimum metabolic rate of A. stuartii at 25°C but not at 5°C and had no significant influence on daily metabolic rate and food energy intake at 5°C or at 25°C. Thyroid secretion rate of A. stuartii was 0.47±0.07 µg I day-' and 0.15±0.02 µg I day-' in animals acclimated to cold and warm conditions. In M. musculus, there was no significant effect of long-term exposure to cold on the rate of thyroid iodine secretion, it being 0.18±0.02 µg I day-' and 0.15±0.01 µg I day-' in the cold and warm conditions respectively. The large increase in thyroid activity in A. stuartii following acclimation to cold could explain the increase in metabolic rate. No periods of torpor in A. stuartii were detected in this study.