The Development Of The Morphology And The Physiology Of Digestion Indigestion Of Takifugu Rubripes

Takifugu rubripes has been taken into account gradually because of its particular economic value and science research. At present, this species is in large scale for aquaculture in China. However, as a new species for aquaculture in our country, the techniques of breed and manufacture of formulated diets are still two major problems. The aim of this work is to supply references for the improvement of formulated diets through study digestive physiology in different developmental stages of Takifugu rubripesThe development of larval and juvenile stage and skin melanophores of Takifugu rubripes were investigated. The whole period of early development Takifugu rubripes lasted about 27 days in spawing water at 15-18℃. The larval stage is from1 to 17 days after hatching, and the juvenile stage is from 17 to 27 days after hatching. At hatching the larval body was covered with larval melanophores in the abdomen. The volume of larval melanophores increased and then decreased with the development of larvae. At 17 days after hatching the larval body appeared small adult melanophores, especially on the surface of the dorsal part, while the abdomen color became silvery white.This paper dealt with the development study on the digestive tract of Takifugu rubripes during early life stages using light microscopy. At hatching, the digestive tract was represented by a more or less undifferentiated straight tube and did not communicate with the exterior, as the mouth and anus were not to be opened yet. At2 days after hatching, a constriction between intestine and rectum that would become the intestino-rectal valve was visible. During the period of endogenous nutrition, the lengthening of the digestive tube and yolk sac absorption were the most conspicuous elements of development. The liver and pancreas were also apparent at this time. At onset of exogenous feeding (3 DAH), yolk sac reserves were not completely depleted, suggesting a period of mixed nutrition and the digestive tract was fullydifferentiated into buccopharynx, esophagus, stomach, intestine and rectum. At 5 DAH, most the yolk sac reserves were completely depleted. The yolks were gradually resorbed and most of them disappeared at day 5, however, in some individuals, they completely disappeared at day 9. The most noticeable events occurring from the 5 DAH to 17 DAH was the transformation of the epithelia type, the differentiation of the pneumatic sac, the epithelial cell, gut convolution, mucosal fold increase and of the growth liver and pancreas. From 17 DAH to 27 DAH, the numbers of the intestine folds and mucus cells increased progressively. From then on, morphological changes of digestive features were almost completed. At 27 DAH, the morphology and function of digestive system were closed to the adult Takifugu rubripes.On the basis of histological observation, the acitivities of some digestive enzymes and alkaline phosphatase were investigated during the different developmental stages of the Takifugu rubripes. Activities of protease and amylase were relatively high at the commencement of exogeonous. And the low protease activities were observed during the complete absorption of yolk sac and metamorphosis. This indicated the activities of protease were associated with the morphology of the developing digestive tract. Amylase activity increased before the first feeding followed by a decreasing and then a rather constant level. Lipase activity remained low during the larvae and juvenile periods. Alkaline phosphatase activity increased gradually. This reflected the development of brush border membranes of enterocytes.After entering the young stage, the digestive system was completed, there were several biotic and abiotic factors influence the levels of digestive enzymes. The objective of the present study was to examine the effects of PH on the activities of protease. The samples have starved for 3 days. And the assays revealed the presence of alkaline proteases from the intestinal section with optimum activity at pH 8.5. While the activities of protease from the rectum and the stomach appeared two peaks. This indicated there might be two groups of proteases with different optimum pH respectively. In hepatopancreas, the optimal pH was 2. Further assays that the samples have starved for 7 days show the optimum activity of the protease in intestinal and liver were still at pH 8.5 and 2 respectively. While the optimum pH ofthe rectum shifted to 8, that of the stomach shifted to 4. This indicated that the stomach and rectum was easy to be affected by starvation.