Morphology and histology observation of the digestive organs and liver of chum salmon（Oncorhynchus keta）

【Objective】To find out the morphological and structural characteristics of the chum salmon’s（Oncorhynchus keta）digestive organs，so as to provide an effective reference for the optimization of artificial breeding feed. 【Method】The morphology and histology of the digestive organs of the second-year chum salmon were taken as objectives. Morphological and histological characteristics were studied using the anatomy and conventional paraffin section techniques.【Result】The digestive tract of chum salmon was composed of oropharynx cavity，esophagus，stomach，pyloric caecum，intestine. The jaw teeth and pharyngeal teeth were well developed in the oropharynx cavity，and the chum salmon had a very coarse and short esophagus with thick muscle layer. The stomach was in a“V”shape，consisting of the cardiac stomach，gastric body and pyloric stomach，with many folds in mucosal. The surface of the gastric mucosal layer was a densely-arranged single layer of columnar epithelial cells. The mucosal layer was inverted to form a large number of gastric pits，and there were abundant gastric gland tissues at the base of the gastric pits. Among them，the cardiac stomach， gastric body of the stomach had more gastric glands，but the pyloric stomach had less. The pyloric caecum was spirally and longitudinally arranged，and its mucosal layer was composed of a single layer of columnar epithelial cells and a large number of goblet cells. The intestine was short，the foregut had thin mucosal folds and the boundary of the mucosal layer was not obvious，and there was no obvious mucosal layer and mucosal fold structure in the hindgut. The liver has no lobes， the boundaries of the liver lobules were blurred，but the structures of central vein and bile ducts were clear.【Conclusion】 The morphological and structural characteristics of the chum salmon’s digestive organs are adapted to its diet function， and had the typical characteristics of the digestive organs of carnivorous fish.