Abstract:This work aimed to investigate the histological structure and mucous cell distributing features in the digestive system of Bahaba flavolabiata. Conventional paraffin sections were used, with H&E and AB-PAS (Alcian blue and periodic acid Schiff reagent (AB, pH 2.5)) staining. The esophagus was crude and short, and the Bu-type stomach was divided into three portions: the cardiac stomach, fundic stomach, and pyloric stomach. There were eight pyloric caeca, and the intestine had two inflections in the body cavity. The histological analysis revealed that the digestive tract wall was composed of serosa, muscularis, submucosa, and mucosa, from the outer wall inwards. The muscularis of the esophagus was thick, but the mucosa was thin, and the epithelium did not have mucous. Muscularis and mucosa of the stomach were thick and composed of simple columnar epithelium, with a gastric gland found in the lamina propria. The pyloric caeca were characterized as having large cavity diameters, and numerous mucosa folds, with very thin muscularis layers. The muscularis in the intestine was thicker than that in the pyloric caeca, with numerous mucosa folds. Here, mucous cells were found in the epithelium. AB-PAS staining revealed that only type Ⅰ and type Ⅱ mucous cells were present in the entire digestive tract of B. flavolabiata, except in the esophagus. Numerous type Ⅰ mucous cells were found in the gastric gland and epithelium of the stomach. Only type Ⅱ mucous cells were found distributed in the epithelium of pyloric caeca mucosa. A large number of type Ⅱ and a smaller number of type Ⅰ mucous cells were found in the intestine. The former were distributed mostly on the surface of the epithelium and the latter in the basal layer of the epithelium. Characteristics of the histological structure and mucous cell distribution in digestive systems are in accordance with the habits and predacity of B. flavolabiata.
