Morphologic characterization of the esophagus of green turtles (Chelonia mydas)

Understanding the morphology and basic physiological processes in Chelonia mydas is extremely important and can provide support for evolutionary studies on the species. The aim of this study was to describe the morphology of C. mydas' esophagus in order to produce data that allows comparative analyses with other turtles. Eight specimens of C. mydas from the coast of Espirito Santo were used during the period from September to November 2014. We obtained the curved carapace length (CCL) and curved carapace width (CCW) in centimetres. The esophagus was completely removed from the insertion region of the oropharynx to the initial portion of the stomach for macroscopic and microscopic evaluation. The measurement on the length and description of the structures in four regions of the esophagus were performed. The entire organ was fixed in 10% formalin and then a one centimetre diameter fragment was collected for histological processing and staining by hematoxylin and eosin (HE), Masson, Gram and periodic acid-Schiff (PAS) techniques. Juvenile animals had average CCL of 38.8 +/- 6.43 cm and average CCW of 35.6 +/- 6.59 cm; the adult animal had a CCL measurement of 102.3 cm and CCW of 96.9 cm. The average length of the esophagus was 20.47 +/- 1.56 in youth, and total 55.6 cm in the adult. It was observed that C. mydas' esophagus is a tubular muscular organ that consists of conical papillae that vary in quantity and size as they approach the stomach, lined by stratified squamous keratinized epithelium and rich in myxoid tissue. There is variation in the mucosal, submucosal, external muscle and serous layers among the four regions of the esophagus and there are mucus-producing glands in the submucosa of the gastroesophageal junction region. The histomorphometric characteristics of C. mydas' esophagus are important to engage the mechanical function and mucosal protection of this organ.