Water Economy and Energy Metabolism of the Sandy Inland Mouse, Leggadina hermannsburgensis

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Abstract
The effects of ambient temperature on oxygen consumption, evaporative water loss, and body temperature, as well as an overall assessment of water metabolism, were studied in the murid, Leggadina hermannsburgensis, from the arid inland of Australia. Under moderate laboratory conditions, this mouse can subsist indefinitely on a diet of air-dry seed, without drinking water; on such a diet mean urine osmotic concentration was 4711 ± sd 842 milliosmoles per liter. The urine to plasma osmotic pressure ratio was 14.6:1 ± sd 7.5, whereas the ratio for urea was 242:1 ± sd 90. Because Leggadina has a high rate of evaporative water loss, it is concluded that the kidney is the primary means of water conservation. Histological evidence of renal morphology supports this view. Energy metabolism and thermoregulatory ability conform to expected mammalian patterns. A short thermal neutral zone extends from Ta of 31 to 36° C, and the basal metabolic rate is 99.0 per cent of that predicted from body weight. Mean body temperature remained stable between Ta of 10 to 35° C, ranging between 37.5 and 38° C. At an ambient temperature of 37° C, animals became hyperthermic with TB of 39.6° C. Thermal conductance below thermal neutrality was constant, but within and above thermal neutrality it was directly related to ambient temperature.

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