Comparative phenotypic and structural adaptations of tongue and gastrointestinal tract in two bats having different feeding habits captured from Saudi Arabia: Egyptian fruit bat (Rousettus aegyptiacus) and Egyptian tomb bat (Taphozous perforatus)

Abstract

Our study was mainly designed to describe the structural and functional adaptations of tongue and gastro-intestinal tract of Rousettus aegyptiacus (Ra) and Taphozous perforatus (Tp) in relation to their diets. Ten adult bats from each species captured and investigated using histological, histochemical and scanning electron microscopy (SEM). Our finding showed that tongue of both species carried mechanical and gustatory papillae. In Ra, the mechanical papillae were subdivided to conical (small and large) and filiform (giant, rousette, leaf-like and spear-like) papillae with regional-specific lingual arrangement. However, there were only two types of filiform papillae in Tp (pronged and crown-shaped). Consistently, though both species carried three vallate papillae at the radix linguae, our histological findings showed comparably varied structure for these papillae. The vallate papillae contained about ten ovoid taste buds in Tp, while it was made up of single barrel-shaped taste bud in Ra. Based on their dietary diversity, the gastro-intestinal tract in both species showed remarkable differences. Importantly, our records revealed that Tp had thicker stomach layers with increased mucosal folding arborization (rugae) than Ra. In addition to significantly increased numbers of branched gastric glands in Tp compared to Ra. Intestinal villi were relatively shorter in Tp with increased numbers of goblet cells than Ra; with different topography in SEM. The gastric mucous cells and intestinal goblet cells were positive for alcian blue stain, while the neutral mucopolysaccharides were detected in the mucosal basal parietal and chief cells and intestinal crypts of Lieberkühn with intense reactions in Tp more than Ra. These findings brought out distinct paradox adaptations in tongues and digestive tracts; based on the dietary and energetic demand for each species.