Morphology and histology of the digestive tract in Cheilinus undulatus

The morphology and histology of the digestive tract of Cheilinus undulatus were investigated by the methods of anatomy,histological sections and optical microscopy.The results showed that the digestive tract of C.undulatus was composed of buccal-pharynx cavity,esophagus,stomach and intestine.There were jaw teeth and pharyngeal teeth in the large buccal-pharynx cavity.The esophagus was very coarse and short.The stomach shaped as I and swelled.There was no pyloric caeca in the pyloric stomach.The intestine was very short,which included anterior intestine,posterior intestine and rectum.The intestinal coefficient was about 3.05.There were microvilli in the cavity all over the digestive tract.The wall of the digestive tract is divided into four layers: mucosa,submucosa,muscle layer and serosa.The epithelium of the digestive tract was composed of simple columnar cells,in which goblet cells were distributed.There was loose connective tissue in the submucosa.There were circular layers of striated muscle in the inner layer of muscle,and the outer layer was longitudinal layers of striated muscle.The nerve plexuses distributed in the muscle layer between the circular and longitudinal layers.The outer surface of the digestive tract was covered by a thin layer of serosa.These characters were accordance with the habits and predacity of C.undulatus.Also,it was easy to break and grind the shell of its food,digest and absorb effectively in a short time.