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

In this article we examine the gut morphology of the only three arid-occurr ing otomyine rodents; Brants' whistling rat, Parotomys brantsii, Littledale 's whistling rat, Parotomys littledalei and the Karoo bush rat, Otomys unis ulcatus and relate this to the semi-arid environment in which they are ende mic. All three otomyine rodents display a gastro-intestinal system well sui ted to a wholly herbivorous diet, with a well-developed caecum and relative ly long large intestine. Despite the broad similarity in the gross gastro-i ntestinal anatomy between the species examined in this study and their mesi c-occurring otomyine counterparts, the results suggest an elongation of the large intestine, with a concurrent reduction in the size of the small inte stine in the arid-occurring species. We argue that this trend may be relate d to water conservation and is supported by the distribution of the three s pecies, with P. littledalei, which occurs in the most arid areas of the thr ee, having the longest large intestine.