RENAL STRUCTURE, AND THE EFFECT OF AN INSECTIVOROUS DIET ON URINE COMPOSITION OF SOUTHERN AFRICAN ELEPHANT-SHREW SPECIES (MACROSCELIDEA)

Most southern African elephant-shrew species, including Petrodromus te tradactylus, Elephantulus myurus, and Macroscelides proboscideus are l argely insectivores though plant material is occasionally eaten. Unlik e the other southern African elephant-shrew species P. tetradactylus d oes not inhabit arid areas of southern Africa but is restricted to coa stal sand-forests. However, all species rely on their food source for water. The renal structure of the above three species (only renal morp hometric data was obtained for E. myurus) displayed characteristics co mmon to arid-adapted species, and there were no clear differences in r enal morphology between the three species. Renal structures of all thr ee species were similar, exhibiting distinct cortical and medullary zo nes, and a single, elongated urinary papilla projecting into the pelvi s with no calices. There was no significant difference in the percent medullary thickness index between the species. There was no significan t difference in urine concentrating ability (UCA) for M. proboscideus and P. tetradactylus with each showing no change in urine osmolality w hen fed a diet of mealworms with and without water. The mean (+/- SEM) urine osmolality when feeding on mealworms only was 3.99 +/- 0.09 mol /kg and 2.96 +/- 0.19 mol/kg for M. proboscideus and P. tetradactylus respectively. Both M. proboscideus and P. tetradactylus had allantoin precipitate in their urine during all stages of the experiment. These results suggest that the latter two species are arid adapted and that there is no difference in UCA when sufficient water is available in th eir diet. Although both species have a kidney structure indicative of a high urine concentrating ability, this study shows that P. tetradact ylus and M. proboscideus when feeding on a diet high in performed and metabolic water, have urine osmolalities similar to more mesic species .