Bioenergetics and body size in dasyruid marsupials.

MACMILLEN, RICHARD E., AND TOHN E:. NELSON. Bioenergetics and body size in dusyurid marsupials. Am. j. Physiol. 2 17(4) : 1246-l 251. 1969.-Basal. metabolic rate, weight-specific conductance, and body temperature were determined in 12 species of the Australian marsupial family Dasyuridae. Animals varied in size from a 7.2-g Antechinus muculatus to a 5,U 50-g Surcophilus harrisii, and came from a variety of habitats and latitudes. The relationship between BMR (in ml 02/g per hr) and body size in dasyurids is inversely linear on a log-log plot and is described by the least-squares equation M = 2.45 W-0*261; a line fitted to this equation is parallel to, but significantly reduced by 32.1 y0 below that for placental mammals. Weight-specific conductance (in ml 02/g per hr per “C) in dasyurids also varies inversely and linearly on a log-log plot with body size; this relationship is described by the leastsquares equation C = 0.914 W--O&~, which is not significantly different from that for placentals. Body temperatures of dasyurids in thermal neutrality averaged 37.2 C in animals more than 100 g, but appeared to be somewhat lower in smaller forms. The few comparative data for other marsupials, together with ours, suggest a lowered BMR may be characteristic of marsupials in general.