Fine structure of the dorsal lingual epithelium in Tarentola annularis and Crocodylus niloticus

Abstract

The present study examined the morphological features, histological and histochemical aspect of the tongue of two reptilian species, Tarentola annularis (family: Gekkonidae) and Crocodylus niloticus (family: Crocodylidea), with different habitats, feeding patterns and behaviours, by light and scanning electron microscope. It was observed, that the bifurcation of the tongue was more visible in Tarentola annularis. Conical and filamentous papillae were observed on the lingual body of Tarentola annularis, while in Crocodylus niloticus both mechanical filiform and gustatory papillae appeared. The lingual mucosa in Tarentola annularis is covered by stratified squamous epithelium and keratinised but in Crocodylus niloticus it is highly folded and more heavily keratinised in the folded region and have a localised thickenings structure resembling taste buds. Mucous glands appeared in Tarentola annularis and compound tubular glands in Crocodylus niloticus. At scanning electron microscopy, abundant microridges and microvilli in both species were exhibited on papillae surface facilitated feeding habits. Histochemically, the tongue of two species is strongly positive for carbohydrate stain but with variable degree with others stains. In conclusion, there is a marked correlation between the structure of the tongue of the present reptilian species, habitats and feeding mechanism of the two species.