Study on the morphology, histology and enzymatic activity of the digestive tract of Gymnocypris eckloni Herzenstein.

The present research was conducted to study the morphology, histology and enzymatic activities of the digestive tract of Gymnocypris eckloni by light and transmission electron microscopes as well as by enzyme assays. The digestive tract of G. eckloni consisted of the oropharyngeal cavity, oesophagus and intestine. The wall of the digestive tract was composed of mucosa, submucosa, muscularis and serosa but lacked muscularis mucosa and glands. The stratified epithelium of the oropharyngeal cavity and oesophagus contained numerous mucous cells. Taste buds were found in the epithelium of the oropharyngeal cavity. A large number of isolated longitudinal striated muscular bundles were present in the submucosa of the oesophagus. The mucosal epithelium of the intestine was composed of simple columnar cells containing absorptive, goblet and endocrine cells. Numerous mitochondria and endoplasmic reticulum were observed in the absorptive cells, especially in the anterior intestine. From the anterior to the posterior intestine, the number and length of mucosal folds and microvilli decreased, but the number of goblet cells increased. The intestinal coefficient was 2.38. Maximum trypsin activity was measured in the anterior intestine, while the lowest lipase and amylase activities were tested in the middle and posterior intestines, respectively. The results provided experimental evidence for evaluating physiological condition of G. eckloni digestive tract, which will be useful for improving current rearing practices and diagnoses of digestive tract diseases.