Morphology of the Tubular Portion of the Digestive Tract of Free-Living Kinosternon scorpioides scorpioides (Linnaeus, 1766)

Abstract

Kinosternon scorpioides scorpioides is an omnivorous chelonian with a wide geographical distribution, occurring from Mexico to South America, especially in Brazil. While morphological observations of the species have described its oesophagus, little is known about the other organs constituting the tubular digestive tract. Therefore, the objective of this study was to describe the morphological aspects of the tubular portion of the digestive tract of this species. Ten adult specimens were analysed. After fixation in 10% formalin, organ fragments were embedded in paraffin using the routine histological technique. Sections of 5 μm thick were stained with haematoxylin–eosin (HE), Gomori trichrome (GT) and Alcian blue (AB) pH 0.4 and 2.5. The tubular portion of the digestive tract of K. s. scorpioides consisted of the oesophagus, stomach, small intestine (duodenum, jejunum and ileum), large intestine (caecum and colon) and cloaca. The wall of the tubular portion of the digestive tract of K. s. scorpioides was made up of four concentric layers: Mucosa, submucosa, muscularis externa and adventitia or serosa. The morphology of the tubular digestive tract of adult K. s. scorpioides described in this study shows structural patterns appropriate to their omnivorous feeding habits, such as a simple glandular stomach, long intestines, a well-developed caecum and the production of mucosecretions throughout the digestive tract. This study provides insights into the digestive physiology of the species and provides data for comparative analyses.