Effect of torpor on the water economy of an arid-zone marsupial, the stripe-faced dunnart (Sminthopsis macroura).
Metabolic rate and evaporative water loss (EWL) were measured for a small, arid-zone marsupial, the stripe-faced dunnart (Sminthopsis macroura), when normothermic and torpid. Metabolic rate increased linearly with decreasing ambient temperature (T(a)) for normothermic dunnarts, and calculated metabolic water production (MWP) ranged from 0.85+/-0.05 (T(a)=30 degrees C) to 3.13+/-0.22 mg H2O g(-1) h(-1) (T(a)=11 degrees C). Torpor at T(a)=11 and 16 degrees C reduced MWP to 24-36% of normothermic values. EWL increased with decreasing T(a), and ranged from 1.81+/-0.37 (T(a)=30 degrees C) to 5.26+/-0.86 mg H2O g(-1) h(-1) (T(a)=11 degrees C). Torpor significantly reduced absolute EWL to 23.5-42.3% of normothermic values, resulting in absolute water savings of 50-55 mg H2O h(-1). The relative water economy (EWL/MWP) of the dunnarts was unfavourable, remaining >1 at all T(a) investigated, and did not improve with torpor. Thus torpor in stripe-faced dunnarts results in absolute, but not relative, water savings.
Cooper
C E
CE
Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia. C.Cooper@curtin.edu.au
McAllan
B M
BM
Geiser
F
F
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001315:Australia; D001834:Body Water / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D003889:Desert Climate; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D008297:Male; D008394:Marsupialia / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D013696:Temperature; D014870:Water Loss, Insensible / Q000502:physiology*
D002245:Carbon Dioxide