The Primary Studies On The Digestive Physiology Of Plectropomus Leopardus Under Industrialized Culture

In this paper, the digestive system of Plectropomus leopardus which are fed with artificial compound feed under industrialized culture, were observed,aiming at not only providing theoretical data and support to the histophysiology of Plectropomus leopardus under this industrialized culture and the research and development of the artificial feed,but also enriching the basic knowledge of digestive physiology of the marine carnivorous fish.Adopting anatomy and histological section technique, this paper studies the morphology and histology of digestive system of Plectropomus leopardus. The digestive tract of Plectropomus leopardus is made up of the oesophagus、stomach、pyloric caeca and intestine, while the wall of digestive tract includes mucous,submucosa lamina, lamina muscularis and adventitia. The Y- shaped stomach is inflated,in which no goblet cells are seen and esophagus and stomach all have well-developed muscularis. Lines between the stomach and foregut, Pyloric whose histological structure is similar to intestinal tract is made up of three fingerlike gibbosities. The intestinal tract lies like “Z” in the abdominal cavity, whose intestinal length ratio is 0.72 ± 0.14.Intestinal mucosal layer protuberates into the cavity, forming developed folds, most of them form secondary folds, the goblet cells are distributed to each section of the intestinal tract. The digestive glands consists of hepato-pancreas and cholecyst. The leaf-shaped liver is separated into three leaves,the pancreas are dispersedly distributed;the gallbladder has a long strip shape. This study discusses the relationship between the histology characteristic of digestive system of Plectropomus leopardus and the digestion and absorption under industrialized culture and considers that the histology of digestive system of Plectropomus leopardus have typical characteristic of digestive system of carnivorous fish. Fragmentation phenomena is found in mucosal layer of digestive tract in the thin fish.The height of mucosal folds of esophagus, stomach, pyloric caecum in the thin fish is higher than normal fish, but the difference is not significant; The height of mucosal folds of the small intestine and rectum in the thin fish is lower than normalfish, while the difference is significant.The esophageal submucosa of thin fish is thicker than the normal fish, but the difference is not significant;The submucosa of stomach,pyloric caeca, intestine and rectum in thin fish is thicker than normal fish, while the difference is super significant.The circular muscle layer and longitudinal muscle layer of esophagus, stomach, pyloric caecum and small intestine in thin fish is thicker than the normal fish, however, rectum is opposite and the difference is super significant.The density of mucosal goblet cell in thin fish is less than healthy fish. In addition, HE staining and oil red O staining were separately implemented in liver tissue of thin and healthy individuals then we found that the liver tissue of thin fish becomes loose, the cells shrink, the storage of fat in liver cells quality is less than healthy individuals,lipofuscin appearing on the liver tissue of thin fish is significantly more than the healthy individuals.Distribution of mucous cells in digestive tracts of healthy individuals and thin individuals were observed and analyzed by the method of histological sections and AB-PAS staining technique. The result shows that mucous cells are distributed in each part of the digestive tract, with the density and type of mucous cell of the same parts are different. Mucous cells in the digestive tract can be divided into type Ⅰ, type Ⅱ, typeⅢ, type Ⅳ. Among them, the mucous cells of esophagus are mainly type Ⅲ;Stomach are mainly typeⅠ; Ryloric caeca and small intestine are mainly type Ⅲ; Rectum are mainly type Ⅲ and Ⅳ.Besides, the order of secretion ability of mucous cells within the unit area of digestive tract is esophagus>rectum>small intestine>pyloric caeca>stomach.The density of the mucous cells in the intestine is closely related to the functions of the different segments in the digestive tract with the comparison of the mucous cells in the each parts of intestine.The thin fish contain less acidic and neutral glycoprotein-secreting cells than normal fish, digestion and antibacterial ability is lower in thin fish than normal fish under industrialized culture is consistent with these observation.Activity of pepsin 、 trypsase 、 amylase and lipase in the digestive organs of Plectropomus leopardus under industrialized culture has been researched,furthermore,the difference of digestive enzymes activity between thin fish and normal fish appeared under the normal circumstances has been compared.The results shows that the activity of pepsin in the stomach is the highest, but have not been detected in the pyloric caeca, intestine and liver and pyloric caeca; the activity of trypsin in the liver is the highest, in the second place are intestine and pyloric caeca, has not been detected inthe stomach; The activity of amylase in the intestine is the highest, in the second place are liver-pancreas and pyloric caeca,the activity of trypsin in pyloric caeca is the lowest,the intestinal amylase activity is significantly higher than other digestive system;the activity of lipase is very low in the digestive system of Plectropomus leopardus,only a little activity is detected in the liver-pancreas. The activity of digestive enzyme in normal fish is significantly higher than thin fish, for proteases, the activity is highly significantly higher in stomach and intestine of normal fish than thin fish, the activity is higher in pyloric caeca and liver-pancreas of normal fish than thin fish, but not significantly; for amylase, the activity is highly significantly higher in digestive system of normal fish than thin fish. In terms of this, the author suggests add digestive enzymes in the feed artificially, but the effect of adding digestive enzymes to the growth of Plectropomus leopardus needs further experimental study.