Study On The Organizational Structure And Related Function Of Digestive System In Poecilobdella Manillensis

The aim of the study is to investigate the morphology, histology and histochemistry digestive tract of Poecilobdella manillensis, and the distribution and characteristics of main digestive enzyme and alkaline phosphatase, also the determination of the aquaculture water temperature on growth of juvenile P.manillensis, Such information of digestive physiology of P. manillensis of notable medicinal importance and with high potential for controlled rearing is considered valuable, not only for providing some theoretical basis on protection of natural resources, artificial bait configuration and artificial cultivation promotion, but also for understanding biology knowledge of the digestive physiology. The main results are as follows:1. The digestive system of P. manillensis consisted of digestive tract and unicellular salivary glands. Digestive tract includes mouth, pharynx, esophagus, crop,intestine, rectum and anus.(1) Mouth with three triangular arranged jaws inside opens in the central part of anterior sucker. These jaws, constituted by radiation and striated muscle and covered by single serration on ridge, can cut the skin of the host. Single-celled salivary glands opening on the mastoid on either side of the jaw secreted hirudin.(2) The globose pharynx is mainly composed of mucosa, developed muscularis and adventitia from inside to outside.(3) Esophagus is short and narrow with a few goblet cells and a large number ofeosinophilic granules on the mucosa layer.(4) There are 10 pairs of contralateral blind sac outstretched from both sides of crop, and the last and longest one extends to both sides of anus.(5) The intestine is no obvious differentiation and can be subdivided into the intestine and rectum. There are several blind sac-like structures in intestinal front cavity, forming ’inner blind sac in intestine’. Mucosa with more glandular cell and developed submucosa is rich in blood vessels and lymphocytes.(6) Rectal cavity is obvious greater than that of intestinal lumen, while its fold height is lower than that of intestine. A few goblet cells can be seen between epithelial cells.2. According to AB-PAS staining, four types of mucous cells are observed in digestive system of the P. manillensis: typeⅠ(red), typeⅡ(blue), typeⅢ(purple reddish) and typeⅣ(blue purple). Mucous cells in oral cavity is dominated by type IV and type III with a small amount of type II and type I. TypeⅢ cells are the major mucous cells in pharynx. There is no mucous cell in esophagus, crop, anterior intestine and rectum. Most of mucous cells in postmedian of intestine are of typeⅠ, but only typeⅡ in anus.3. Distribution and activity of digestive enzymes and AKP in digestive system of P. manillensis.(1) Regardless of satiation or starvation in the esophagus, digestive enzymes activities were significantly lower than that of other parts(P<0.05), the activitties of alkaline phosphatase was intestine > craw > rectal.(2) Satiety, three digestive enzymes activities in different organs were all in the order of intestine > rectal > crop, which protease activity in the intestine is 3.98 times of the rectum, is 23.29 times of the crop.(3) Starvation, the activitties of protease and lipase were intestine > rectal > craw,the activity of amylase was crop > intestine > rectum, lipase activity in the intestine and the crop is higher than the protease activity.(4) The protease and alkaline phosphatase activity increased with the increase of temperature, and reached the maximum at 32 degrees. Amylase and lipase increased at first and then decreased with the increase of temperature. The optimum temperature for amylase was about 26 degrees, and the lipase was about 29 degrees, the activities of digestive enzymes in Poecilobdella manillensis were in the order of protease > lipase >amylase.(5) The optimum p H for amylase, lipase, protease and alkaline phosphatase were7.5, 6.5~7.0, 7.5~8.0, respectively.(6) Histochemistry showed that there is a strong activity of alkaline phosphatase in crop and intestinal epithelial cells.4. When the breeding water temperature at 32 degrees and 29 degrees, the specific growth rate and the growth rate were significantly higher than other groups(17 degrees,20 degrees, 23 degrees, 26 degrees, 35 degrees)(P<0.05). When the breeding water temperature at 26~32 degrees, The survival rate of P. manillensis is more than 86%.The specific growth rate and the culture temperature fitting regression showed that there was a significant relationship between the quadratic function(P < 0.05). The relationship between the specific growth rate and the culture temperature was y=-0.0142x2+0.8464x-8.7751(R2=0.9328). 30.4 degrees is the most suitable culture temperature of P. manillensis.5. The silver niterate method of grimelius were used to investigate the morphology and distribution of argyrophil cells in digestive tube of Poecilobdella manillensis. The distribution density of argyrophil cells was counted according to the distribution characteristics. The results showed that in addition to the esophagus, all parts of the digestive tube possessed the silver cells which stained with brownish black or black. The argentaffine cells were seen between epithelial cells of mucosa layer and the bottom of epithelial cells, the shape of argentaffine cells were circle, ellipse,tapering, strip and so on. Some argyrophil cells had distinct cytoplasmic processes,black particle was visible in cells. Jaw possessed highest cell density in argyrophil cells,and then crop possessed higher cell density and rectum was the last, none silver cells in esophagus were tested. the morphology and distribution of argyrophil cells density digestive tube were closely related to its feeding and digestive physiological activities.