MACRO AND MICROSCOPIC CHARACTERIZATION OF THE TONGUE AND ESOPHAGUS OF SEA TURTLES (TESTUDINES)
Chelonia mydas. Caretta caretta. Histology. Stereology. Papillae.
There is only a little information about macro and microscopic morphology of the gastrointestinal tract of sea turtles, considering that all species are classified under some level of threat of extinction. In this context, it can be considered that studies on the basic biology of these animals allow us to make important management decisions for conservation. There is still a shortage of information relating food habits with the internal morphology of the upper gastrointestinal tract (tongue and esophagus) of these animals. In addition, there are no studies that prove the function of the tongue in the digestion process. For this reason, the present work aims to characterize the macro and microscopic morphology of the sea turtle's tongue and esophagus, establishing comparisons between species and their eating habits. During the period from January 2018 to November 2019, were evaluated the tongue and esophagus of stranded sea turtles that died or accompanied death at the PCCB-UERN Rehabilitation Base, along the coast of RN and east coast of CE. The animals were necropsied and the organs of interest were dissected together and fixed in 10% formaldehyde. Subsequently, the photographic record, weighing and biometrics were performed and then, as the tongue was sent for histological cleavage, the esophagus was sent for the processing of the stereological technique. As a result, there are unpublished histological findings regarding the sea turtle tongue. It was observed that the dorsal surface is covered by keratinized stratified epithelium with papillae in a filiform and fungiform format. The lamina propria resulted from loose connective tissue with the presence of nerve plexuses and blood vessels. The musculature of the tongue is distributed in two orientations, longitudinal and transversal. In C. mydas, salivary glands were observed in the posterior region of the tongue. In the same region, C. caretta showed non-keratinized stratified squamous epithelium with goblet cells, findings that improved the secretion of saliva and mucus by the organ. In the esophageal stereological analysis, it was observed that C. mydas species has higher volume density (Vv) and total volume (Vtot) in the muscular layer, while C. caretta species, present higher values for the mucous layer. From the findings, it can be inferred that the tongue probably assists in chemical digestion and that the esophagus presents morphological and functional differences between the
two species.