Abstract:This study aimed to investigate the morphological and histological features of the digestive system of Schizothorax biddulphi using conventional HE-stained paraffin sections. The digestive system of S. biddulphi consisted of a digestive tract and a digestive gland. The digestive tract comprised the oropharynx, esophagus, and intestine (anterior intestine, middle intestine, posterior intestine, and rectum). A pharyngeal tooth had developed in the oropharynx, but no stomach was present; the intestine adjoined the esophagus and the anterior intestine was inflated. The general structure of the digestive tract consisted of the mucosa, submucosa, muscular layer and serous membrane; however, the oropharyngeal cavity only had the mucosa and muscular layer. The mucosal layer showed the greatest difference, mainly in the following aspects. First, the tunica mucosa of the oropharynx was made of a stratified squamous epithelium with taste buds and numerous mucous cells. Second, the esophagus was thick and short, and the mucosa consisted of a stratified squamous epithelium. Third, there was a large number of blood vessels in the lamina propria. Last, the intestinal epithelial cells were single columnar epithelial cells, and the number of goblet cells increased gradually from the anterior intestine to the rectum, while the mucosal fold height gradually decreased. The digestive gland of S. biddulphi is composed of a liver and pancreas. The hepatic lobule of the liver was not obvious, but the distribution of hepatic sinuses and central veins was regular, however, the portal area of the liver was not typical. The pancreas was an independent structure, separated from the liver, and not found in any tissue other than the mesentery. The veins were more obvious in the pancreatic lobule, and there were numerous nucleated red blood cells in the vascular system. The relationship between morphological and histological features of the digestive system and feeding behavior of S. biddulphi was discussed, in order to enrich the biological research of S. biddulphi and to provide a theoretical basis for the analysis of its trophic behavior and development of its bait.
