Histology of the digestive system in Cheilinus trilobatus
Cheilinus trilobatus is a species of family Labridae with significant economic value in tropical sea.In this paper,the structural characteristics of the digestive tract of C.trilobatus are discussed,as well as the relationship between its organizational characteristics and feeding habits.The digestive tract of C.trilobatus consists of oral-pharyngeal cavity,esophagus,small intestine,and rectum.The oral-pharyngeal cavity is the initial part of the digestive tract and consists of uniseriate jaw teeth and a pharyngeal tooth.These teeth are tough and strong,enabling C.trilobatus to crush the hard shells of crustaceans and mollusks.Moreover,it has one pair of epiglottis teeth,triangularly shaped from left to right and symmetrically distributed.In additional,its hypopharyngeal teeth are healed by granular teeth in a"T"shape and the gut is short and thick with zigzag pattern in body cavity.Based on observation and measurement,we find that the average ratio between the length of intestine and the body length is 0.32±0.11.The digestive gland consists of the hepatopancreas and gallbladder.The liver with dispersed pancreas is divided into three pieces,large in the middle and small on both sides,which are wrapped around the small intestine.The gallbladder is elliptical in shape and located in the lower ventral lobe of the liver.The common hepatic duct is in the anterior part of the small intestine after the esophagus and connected to the small intestine and the average ratio between the weight of the liver and pancreas(1.43±0.32)％.As the oropharyngeal cavity,the wall of the cavity is smooth and composed mainly of mucosal layer.The surface layer of the wall contains taste buds and a small number of cup-shaped cells.The mucosal layer is composed of compound flat cells,and the oropharyngeal cavity has a well-developed muscular layer that consists of an outer circular muscle and an inner longitudinal muscle.The longitudinal layer is discontinuous and fasciculated,and the muscle layer is covered with a layer of plasma membrane.The oropharyngeal cavity is not clearly demarcated from the submucosa,and the intermuscular nerve plexus can be seen between the two layers.The esophagus consists of four layers,including mucosal layer,the submucosal layer,muscular layer,and plasma layer.Meanwhile,muscle layer is one of most prominent features of digestive tract of C.trilobatus.Additionally,the intermuscular nerve plexus can be seen between the two layers,suggesting that this layer plays a crucial role in the digestive process.The muscular layer is particularly well developed,which is indicative of the importance of muscular contractions in the digestion of food.The mucosal layer is another important component of the digestive tract of C.trilobatus.It is composed of secondary and tertiary finger-like projections,and the base is commonly"concave"like the structure of exocrine glands.The mucosal layer is mostly primary and secondary finger-like protrusions,consisting of a single layer of columnar epithelial cells with a large number of mucous cells distributed in the middle and occasional pear-shaped cells.No intestinal glands were seen,which suggests that the mucosal layer is primarily responsible for the absorption of nutrients rather than secretion of digestive enzymes.The submucosal layer is also an essential component of the digestive tract of C.trilobatus.It contains mostly eosinophilic granular cells whose cytoplasm is stained red by eosin.This layer likely plays a role in the production of mucus.The outermost layer of the digestive tract is composed of a plasma layer.While less prominent than the other layers,the plasma layer likely serves a protective function,preventing damage to the underlying layers.The structural features of the digestive tract,including well-developed muscular layer,mucosal layer,submucosal layer,and plasma layer,all play crucial roles in the digestive process of C.trilobatus.
万方数据
维普
