The Post-Embryonic Development of Digestive System and the Demand of Energy of Hucho taimen

With the technology of morphology,histology and nutrition,the characteristics of organ development and the source and demand of nutritional at different stages in post-embryonic(water temperature 3-14℃)of Hucho taimen were discussed.The results showed that the membrane of H.taimen fertilized ovum was ruptured in 30 d,the prototype of U-type stomach was formed,the mouth could open and close freely,and nutrition was supplied from its yolk sac.The membrane ruptured after 8 d,teeth formed,and anus communicated with outsiders.The oropharyngeal cavity,esophagus,U-type stomach,intestine,and anus initially formed in the digestive tube,which nutrition was supplied from the huge yolk sac.The membrane ruptured after 16 d,pancreas and pyloric caeca appeared,larvae could intake and digest exogenous food,fish mixed nutrition,which was from yolk sac and outsiders,mainly depended on endogenous.The membrane ruptured after 24 d,the fish began floating and intaking actively,the fish mixed nutrition which mainly depended on exogenous.The membrane ruptured after 30 d,the yolk sac was completely absorbed,the function and structure of each digestive organs developed consummately,fish was from mixed nutrition into the stage of exogenous nutrition,the nutritional need of juveniles was below 10% fat,level of the optimal protein was 50%.