Thermal, metabolic, hygric and ventilatory physiology of the sandhill dunnart (Sminthopsis psammophila; Marsupialia, Dasyuridae).
We present here the first physiological data for the sandhill dunnart (Sminthopsis psammophila), the second largest (35-44 g) sminthopsine dasyurid marsupial, and report torpor for this species. Their thermoneutral body temperature (34.4 degrees C), thermolability below thermoneutrality (0.062 degrees C degrees C(-1)), and mild hyperthermia above thermoneutrality (35.5 degrees C) are typical of small dunnarts, and dasyurids. Basal metabolic rate (0.80 mL O2 g(-1) h(-1)) is as predicted from mass. Sandhill dunnarts generally conform to the Scholander-Irving model of endothermy, although metabolism increases less than expected and extrapolates to a higher than actual body temperature.Wet (0.22 mL O2 g(-1) h(-1) C(-1)) and dry (2.8 J g(-1) h(-1) degrees C(-1)) thermal conductances were as predicted. Thermoneutral evaporative water loss (1.6 mg g(-1) h(-1)) was only 54% of expected, but this is not significantly different, and more likely reflects variability in the marsupial dataset than an adaptation.Relative water economy resembles that of other small marsupials, rodents and birds, with a point of relative economy of 18 degrees C. Respiratory ventilation closely matches metabolic rate, with minute volume increased at low ambient temperatures by increased breathing rate rather than tidal volume; oxygen extraction was constant at about 17%, except during hyperthermia above the thermoneutrality. Torpor conferred significant energetic and hygric benefits. We found no evidence of deviation from allometrically- and phylogenetically-based expectations despite the sandhill dunnart's arid habitat and large (for a dunnart) body mass.
Withers
Philip C
PC
Animal Biology, University of Western Australia, Stirling Highway, Crawley, Western Australia 6009, Australia. pwithers@cyllene.uwa.edu.au
Cooper
Christine E
CE
D000818:Animals; D005260:Female; D008297:Male; D008394:Marsupialia / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature