Morphological description of the oropharyngeal cavity of Kinosternon scorpioides scorpioides (Linnaeus, 1766), (Testudines: Kinosternidae)

The oropharyngeal cavity of turtles exhibits considerable morphological diversity associated with differences in habitat, diet, and feeding strategies. However, the structural organization of this region remains poorly characterized in many Testudines, including Kinosternon scorpioides scorpioides, therefore, we aim to characterize the morphological aspects of the oropharyngeal cavity of K. s. scorpioides reported using macroscopic descriptions, light microscopy (LM) and scanning electron microscopy (SEM). LM revealed that almost the entire epithelium lining the oropharyngeal cavity of K. s. scorpioides is of the non-keratinized stratified mucous type, containing many mucous cells and numerous mucous glands throughout the lingual epithelium, palate and floor of the mouth, with the exception of the region located near the rhinopharynx, which presented a stratified keratinized squamous epithelial tissue containing taste buds, not observed on the tongue. SEM revealed that the entire epithelium of the oropharyngeal cavity has pores that are likely associated with the mucous glands observed in LM, and the surface of the tongue is covered by voluminous lingual papillae of varying sizes and shapes (filiform and fungiform types), which had cells covered by microvilli and/or microcysts. No salivary glands were observed. Compared with morphological data from other species, this study indicates that the epithelial structure of the oropharyngeal cavity of K. s. scorpioides is consistent with that observed in other generalist omnivores with semi-aquatic habits, thus corresponding to ecological information about this species.