Kidney Structure in Two Species of Arid Zone Rodent: Lakeland Downs Short-Tailed Mouse, Leggadina lakedownensis, and the House Mouse, Mus domesticus

Abstract

Native rodents that inhabit the arid zones of Australia produce amongst the most concentrated urines recorded in an effort to conserve water during periods when it is scarce (Mac MiiJen and Lee 1967; Hewitt 1981). Their ability to survive in the absence of free water has been inherently associated with the morphology of their kidneys. Sperber (1944) developed the relative medullary thickness (RMT) index to compare the size of the medulla, and hence the concentrating ability of the kidney among mammalian species. This concept was extended further by Schmidt-Nielsen and O'Dell (1961) and later by Greenwald (1989) and Beuchat (1990), who compared absolute and RMT with the maximum urine osmolality of mammals.