Kidney structure of a euryhaline mammal, the Cape clawless otter (Aonyx capensis)

The Cape clawless otter (Aonyx capensis) is one of the few species of mamma ls that occur in both freshwater and marine habitats, and it therefore must be able to tolerate the high rates of water flux typical of aquatic animal s as well as the desiccating effects of seawater. The clawless otter has pa ired, discrete multirenculate kidneys (total mass = 172 g) comprised of bot h unipapillary and bipapillary renculi weighing an average of 2.6 and 3.2 g , respectively. The average thickness of the cortex is 2.3 mm, and thicknes ses of the outer and inner medulla are 2.4 and 6.4 mm, respectively. These measurements and the overall structure of the kidney of the Cape clawless o tter are intermediate between those of freshwater and marine mammals.