Anatomical studies of the gastrointestinal tract of the striped sand snake (Psammophis sibilans)

Abstract

A study was carried out on the gross anatomical, morphometric features and histology of the gastrointestinal tract of the Striped Sand Snake (Psammophis sibilans). Ten snakes (five males and five females) were euthanized and dissected for the study. The gastrointestinal tract appeared as a straight tubular organ from oral cavity to cloaca, owning to the absence of a cecum. The stomach could be distinguished as a spindle-shaped bulge along the length of the gastrointestinal tract, longitudinal folds (rugae) were observed for the inner wall of the stomach. The small intestine in this species is thrown into rings; the cranial portion is the duodenum and posterior portion the ileum. The ileum widens up into the colon, it also loses its rings at this point. The cranial portion of the large intestine is the colon, and the caudal portion is the rectum. The mean snout-vent length (cm) in males was recorded as 94.02 ± 1.1 while in females it was recorded as 48.28 ± 1.4. The stomach was the shortest segment while the esophagus was the constituting almost half of the total length of the snout-vent length. The wall of the esophagus, stomach, small intestine and large intestine was built up of the following layers from outside inwards; serosa, muscularis, submucosa and mucosa, while the stomach consists of a new layer, subserosa which follows the serosa. The entire length of the gastrointestinal tract was lined by simple columnar epithelium (ciliated in the esophagus) and contains goblet cells except in the stomach and rectum where these cells are absent. The esophageal mucosa contained extensive folds, and the lining epithelium consisted of ciliated columnar epithelium, lamina propria, muscularis mucosae and goblet cells. Areas of lymphatic aggregation were also found in the mucosal layer. The stomach mucosa is thrown into folds and was lined through its length with columnar epithelium that showed numerous invaginations, gastric pits, which led to glandular structures, the gastric glands. In the small intestine (duodenum and ileum) the mucosal lining of the intestinal villi is uniform throughout. It is composed of three types of cells; simple columnar cells, goblet cells and lymphatic nodules. The large intestine consists of the colon and rectum. With their villi relatively short compared to those in the small intestine.

Keywords: Sand snake, Psammophis sibilans, gastrointestinal tract, gross, morphometry, histology