Molt stages and changes in digestive enzyme activity in hepatopan-creas during molt cycle of Chinese mitten crab,Eriocheir sinensis

The molt cycle of the Chinese mitten crab Eriocheir sinensis was staged by the method of Darch.We then measured the three digestive enzymes in hepatopancreas throughout the molt cycle.Based on the setogenesis and the morphological changes to the epidermis of the third maxilliped,we identified four molting periods(post-molt,intermolt,premolt and ecdysis).In addition,the premolt period was further divided into three substages(D0,D1,and D3-4).Both amylase and tryptase activities increased in the hepatopancreas during the A-B stages,peaking in the early premolt D0 stage(P0.05),and then gradually decreasing in the later premolt D3?4 stage(P0.05).There were no obvious changes in peptase activity during the majority of the molt cycle,though levels were sig-nificantly lower(P0.05) in the later premolt D3-4 stage.In summary,we identified five periods(C,D0,D1,D3-4,A-B)in the molt cycle of E.sinensis during which the activities of amylase,trypsase,and peptase changed peri-odically.