Abstract:Mastacembelus armatus is primarily distributed in the Yangtze River and aquatic systems in the south of China, and is affiliated with Mastacembelus, Mastacembelidae, and Symbranchiformes. It has great economic value and breeding prospects owing to its high meat quality and balanced nutritional content. However, with overfishing and human influences on its habitat, the population of M. armatus has gradually decreased. We characterized the morphology and histology of the M. armatus digestive tract, aiming to investigate the relationship between the morphological and histological features of the digestive tract and its feeding behavior. Anatomy, paraffin sections, HE staining, and stomach content analysis were used to study samples collected from the Dongjiang River and Taojiang River in Ganzhou, Jiangxi Province. The results indicated that the digestive tract was composed of the oropharyngeal cavity, esophagus, stomach, and intestine. The oropharyngeal cavity contained the tongue, pharyngeal bone, and callous pad. The mucosal surface of the esophagus was covered with squamous epithelial cells, and the inner wall was full of longitudinal folds and secondary branches. The muscle layer consisted of striated and smooth muscles. The gastric wall and intestinal wall were composed of the mucosal layer, submucosa, muscle layer, and serosal layer. The mucosal layer was a single layer of the columnar epithelium, and the muscle layer was a smooth muscle that was divided into circular and longitudinal muscles. The “V-shaped” stomach was divided into the cardia, gastric body, and pylorus. The thickness of the muscular layer in each part was significantly different. There were no goblet cells in the mucosa, but many glands were located in the cardia or body of the stomach. The gastric pylorus muscle layer was extremely developed. There were two pyloric caeca between the stomach and intestine. The intestine had a curve and included three parts: The foregut, midgut, and hindgut. The average intestinal coefficient of M. armatus was 0.325±0.050. There were significant differences among the anterior, middle, and posterior intestinal villi. Nine prey items were identified in the digestive tract of M. armatus, including shrimp, aquatic insects, fish, snails, eggs, and plant detritus. The average percentage of the stomach fullness index was 2.86%. The prey diversity H’ was 2.19, and prey dominance D was 0.33. Shrimp were dominant in the stomach contents, accounting for the relative importance index percentage of 97.75%, numerical percentage of 92.29%, and quality percentage of 73.07%. In conclusion, the histological structure of the digestive system of M. armatus is related to its function and feeding habits. This study provides a theoretical basis for wild resource conservation and nutrition research on M. armatus.
