Morphological and histological observations of digestive system of cobia Rachycentron canadum

The morphology and histology of the digestive system of Rachycentron canadum was studied using anatomy and light microscope. The results showed that the digestive tract in R. canadum was consisted of buccal-pharynx cavity, esophagus, stomach, pyloric caeca, foregut, midgut and hindgut. The buccal-pharynx cavity was large, and its mucosa was composed of stratified squamous epitheliums with a few goblet cells. The oesophagus was very short, and stratified and simple columnar squamous epitheliums were identified. The stomach was expanded and Y-shaped and many goblet cells were observed in the epitheliums of cardiac stomach and pyloric stomach. Many gastric glands cells were found under the mucosa of the stomach. The pyloric caeca were very developed, and the intestines was short and divided into three parts: foregut, midgut and hindgut. The average intestinal coefficient of R.canadum was calculated, which was about 0.43. From foregut to hindgut, the number of goblet cells and intestinal villus reduced gradually. The digestive glands were composed of liver and pancreas. The liver lobule was not clear but its hepatic cells were rich in fat. Pancreas was diffused and the exocrine section of pancreas was consisted of many pancreatic acinar cells. The pancreas islets were located in the exocrine section.