COMPARATIVE STUDY ON MORPHOLOGY AND HISTOLOGY OF DIGESTIVE SYSTEM OF SILURUS LANZHOUENSIS AND CATFISH (SILURUS ASOTUS)

To investigate the characters of the digestive system structure of Silurus lanzhouensis and enrich its reference information, a comparatively research on the morphology and histology of digestive system between Silurus lanzhouensis and catfish (Silurus. asotus) was performed. The results showed:1. The morphology of digestive tract and digestive gland of Silurus lanzhouensis was similar with those of catfish (Silurus asotus), which was characterized as carnivorous fish, suggesting the shorter digestive tract and stronger "U" type stomach. Besides, pyloric caecum was not found. They both had short and thick gut in which foregut was thicker than hindgut. The liver and pancreas in the both species were observed to be independent and pyknotic. 2. The higher relative gut length (RGL), the lower hepatosomatic index (HSI) and stomach index (STI) was found in Silurus lanzhouensis, compared with those of catfish (S. asotus) (P < 0.05). There was no significant difference observed in the gut index (GI) between the both two species (P>0.05). 3. The larger fold amplitude and the thicker circular muscle layer were found in the stomach of catfish (Silurus asotus) in comparison with that in Silurus lanzhouensis. The numerous plica and the strong mucosal folds was found in the foregut of both two species, although those in catfish (Silurus asotus) was denser. The gut diameter, the number and height of fold was decreasing from foregut to hindgut. The goblet cells and columnar cells were distributed on the mucous membrane layer. In the hepatopancreas of the both species, the lack of connective tissue between the hepatic lobule led to the unconspicuous dividing line. Moreover, the density of hepatocyte was larger in Silurus lanzhouensis than that in catfish (Silurus asotus). Overall, Silurus lanzhouensis had the similar digestive system with catfish (Silurus asotus), which was characterized as carnivorous fish, but the digestive ability of Silurus lanzhouensis was weaker. It might be one of the reason why Silurus lanzhouensis had the narrower distribution and weaker adaptability than catfish (Silurus asotus).