Development of endothermy and non-shivering thermogenesis in the Tasmanian bettong: a review

The Tasmanian bettong (Bettongia gaimardi) is a small marsupial able to increase its heat production (and thus its metabolic rate) by non-shivering thermogenesis. Oxygen consumption increases in response to various stimuli: vasopressin, nor-epinephrine, both alpha(1) and beta adrenergic stimulation, thyroid hormone and cold acclimation (CA) (4-5 degrees C for 14 days). Moreover, the metabolic rate response to nor-epinephrine is enhanced after CA (71% increase 'v' 47% prior to CA). The ability to respond to these stimuli appears only after week 10 of the 15-week pouch life. We have attempted to identify the source and cause of the metabolic response. Brown adipose tissue and the uncoupling protein are totally absent in this species, as in most marsupials. Our research led us to investigate skeletal muscle as a source of heat production in this species and further research into this tissue's involvement in non-shivering thermogenesis seems appropriate.