Moro D, Bradshaw S D
Department of Zoology, University of Western Australia, Perth, Australia.
J Comp Physiol B. 1999 Sep;169(6):419-28. doi: 10.1007/s003600050238.
The coexistence of the Lakeland Downs short-tailed mouse Leggadina lakedownensis and house mouse Mus domesticus on Thevenard Island, in the arid north of Western Australia, prompted a study to compare their seasonal water and sodium metabolism using tritiated water and sodium-22 as tracers. Fractional water influx rates for M. domesticus (40.3 +/- 1.6% total body-water day-1) were significantly higher than those for L. lakedownensis (25.3 +/- 1.2% total body-water day-1). Water effluxes were higher in both species of mouse after the passage of a cyclonic storm near the study site. Water flux differences remained significant between species when turnover rates were scaled with body mass. A comparison of water influx rates of M. domesticus with those predicted for field populations of other eutherian rodents showed that rates for M. domesticus on Thevenard Island were higher than expected. In contrast, water influx rates for L. lakedownensis did not differ significantly from expected values for a desert rodent. Rates of sodium influx for M. domesticus (41.7 +/- 3.6 mmol kg-1 day-1) were over twice those of L. lakedownensis (19.7 +/- 4.8 mmol kg-1 day-1), and were reflected in the significantly higher concentrations of sodium ingested in the diet, and excreted in the urine, of M. domesticus. Furthermore, the rate of water influx was positively correlated with the rate of sodium influx in M. domesticus, suggesting that they were obtaining both water and sodium from the one dietary source. There was no evidence to suggest that mice of either species were experiencing water or sodium stress, because water and sodium influxes and effluxes remained in balance. These results suggest that M. domesticus on Thevenard Island had a higher-than-expected daily water requirement, and may represent a mesic deme of house mice that have yet to adapt to the island environment.
在西澳大利亚干旱的北部地区，拉克伦唐斯短尾鼠（Leggadina lakedownensis）和家鼠（Mus domesticus）共存于西维纳德岛，这促使开展一项研究，使用氚化水和钠 - 22作为示踪剂来比较它们的季节性水和钠代谢。家鼠的水分数流入率（40.3±1.6%总体水/天）显著高于拉克伦唐斯短尾鼠（25.3±1.2%总体水/天）。在研究地点附近有气旋风暴经过后，两种小鼠的水流出量都更高。当周转率按体重进行标度时，物种间的水通量差异仍然显著。将家鼠的水流入率与其他真兽类啮齿动物野外种群的预测值进行比较，结果表明西维纳德岛上家鼠的水流入率高于预期。相比之下，拉克伦唐斯短尾鼠的水流入率与沙漠啮齿动物的预期值没有显著差异。家鼠的钠流入率（41.7±3.6 mmol·kg⁻¹·天⁻¹）是拉克伦唐斯短尾鼠（19.7±4.8 mmol·kg⁻¹·天⁻¹）的两倍多，这反映在家鼠饮食中摄入的钠以及尿液中排泄的钠浓度显著更高。此外，家鼠的水流入率与钠流入率呈正相关，表明它们从同一饮食来源获取水和钠。没有证据表明任何一种小鼠正经历水或钠胁迫，因为水和钠的流入与流出保持平衡。这些结果表明，西维纳德岛上的家鼠每日需水量高于预期，可能代表了尚未适应岛屿环境的家鼠的一个中生种群。
