Abstract:
Abstract-l. The cloaca1 and bucco-pharyngeal regions of three species of Australian freshwater turtles were ex~~mentaily compared for their ability to take up mdiocaIci~ directly from the aquatic medium. 2. The cloaca1 route was at least 4 times more important than the bucco-pharyngeal route for radiocalcium uptake, in each of the three species investigated. 3. Histological examination of anatomical regions in the cloaca showed that the cloaca1 bursae of three species (E. dentata, C. longicollis and E. signata) had abundant villi and infolded mucosal epithelia that increase the surface area of the epithelium exposed to the aquatic medium. 4. Electron microscopic studies on the mucosal epithelium of the cloaca1 bursae showed that it contained many structural characteristics indicative of an exchange function and consistent with the cloaca1 bursae being an important site of radiocalcium uptake within the cloaca.
