Gut morphology of the Otomyine rodents: an arid-mesic comparison

In this article we examine the gut morphology of the only three arid-occurring otomyine rodents; Brants' whistling rat, Parotomys brantsii, Littledale's whistling rat, Parotomys littledalei and the Karoo bush rat, Otomys unisulcatus and relate this to the semi-arid environment in which they are endemic. All three otomyine rodents display a gastro-intestinal system well suited to a wholly herbivorous diet, with a well-developed caecum and relatively long large intestine. Despite the broad similarity in the gross gastro-intestinal anatomy between the species examined in this study and their mesic-occurring otomyine counterparts, the results suggest an elongation of the large intestine, with a concurrent reduction in the size of the small intestine in the arid-occurring species. We argue that this trend may be related to water conservation and is supported by the distribution of the three species, with P. littledalei, which occurs in the most arid areas of the three, having the longest large intestine.