Osmoregulation in African mole-rats : an evaluation of water retention abilities in a subterranean rodent family

Abstract

Subterranean mammals inhabit and thrive over a range of environmental aridities and, as such, are exposed to varying water availability, which they obtain through their diet of underground geophyte storage organs. Evolutionary studies have conclusively shown that kidney and gastrointestinal tract adaptations have enabled increased water absorption under water stress events such as those experienced by small mammals living in arid environments. This chapter attempted to uncover if the subterranean African mole-rat family, the Bathyergidae, possessed the predicted kidney and gastrointestinal tract adaptations in response to their experienced aridity. Unlike terrestrial living small mammal species, African mole-rats, regardless of the aridity they experience, possess similar capabilities of saving water due to comparable urine concentrating and faecal dehydrating abilities likely as a consequence of the similar morphological and anatomical structures of their kidneys and gastrointestinal tract. This strongly supports the Behavioural Osmoregulation Hypothesis, which posits that group-living, instead of kidney and gastrointestinal tract adaptations, has allowed some African mole-rats species to persist in arid environments. Furthermore, this chapter suggests that the capacity of a mammal to become social may lead to a social buffering effect against desertification due to climate change.