Digestive system of the Laotian rock rat Laonastes aenigmamus (Rodentia: Diatomyidae) from the evolutionary viewpoint

Abstract

A preliminary study of the gastrointestinal tract of Laonastes aenigmamus Jenkins et al., 2005 has been carried out. We have revealed that Laonastes is the smallest folivorous mammal with the enlarged forestomach, which is similar to that of certain herbivorous marsupials. The stomach of this rodent contains 70% of the digesta and performs the main role in storing and digesting of plant foods. Laonastes is a unique rodent having such the digestive system, and its herbivory is confirmed by the enlarged ampulla duodeni, small dimensions of the hindstomach (pars pylorica), the absence of vesica fellea, the presence of colon spiral loops, the well-developed lymphoid tissue of stomach, and the gut mass making up to 25–27% of the entire body mass. Such the gastrointestinal tract might have evolved as a result of a general digestive strategy of the foregut mammals that inhabited tropical forests in the Miocene. This strategy involved an adaptation to the nutrition on leaves of tropical dycots which apparently contributed to the convergent evolution of the digestive system in different folivorous mammals.