Correlates of torpor in the insectivorous dasyurid marsupial Sminthopsis murina.

Abstract

Body temperatures, oxygen consumption and the thermal response of liver mitochondrial membranes of the Common Dunnart, Sminthopsis murina, were measured during winter and the summer mating season. In winter body temperatures for S. murina during spontaneous torpor were as low as 15oC and oxygen consumption was reduced to 6% of normothermic resting animals. In summer animals remained normothermic. For the winter animals liver mitochondrial succinate oxidase and succinate: cytochrome c reductase showed a constant apparent Arrhenius activation energy (Ea) over the temperature range 6 to 40oC. For summer animals Ea increased below about 20oC. The temperature coefficient for the motion of spin labels intercalated with membrane lipids increased below about 8oC for membranes from winter animals and below 20oC for summer animals.