Histochemical studies on the mucins of the vertebrate tongues. VIII. Histochemical analysis of mucosubstances in the tongue of the turtle.

The tongue of the fresh-water turtle, Geomyda trijuga, was investigated histochemically to determine the localization and nature of mucosubstances in it. The results were considered in comparison with the lingual mucosubstances of other vertebrates. A heterogenous distribution of neutral mucosubstances, sulphomucins, sialomucins and hyaluronic acid in various lingual sites was noted. The anterior half of the lingual surface was keratinized, whereas on the posterior half numerous broad papillae and three types of goblet cells were found. The lingual salivary glands were absent from the turtle tongue. The importance of lingual histology in establishing the phylogeny of vertebrates and the possible functional significance of mucosubstances in the physiology of gustation are discussed.