Activities of digestive enzymes during embryonic development in the crayfish Procambarus clarkii (Decapoda)

The red swamp crayfish, Procambarus clarkii (Girard), has become an important freshwater species for Chinese inland aquaculture because of its high commercial value and consumer demand. The aim of this study was to gather information about the activity of digestive enzymes at different embryonic stages of P. clarkii in order to increase our knowledge about digestive physiology and to guide technology for maternal culture so as to improve the hatching rate. Embryonic developmental stages were divided into six stages: I, fertilized egg; II, cleavage and blastula; III, gastrula; IV, egg nauplius; V, eye pigment forming; and VI, prepared for hatching. Pepsin-specific activity decreased significantly from stage I to stage IV. Although it increased at stage V, the activity level declined again before hatching. Both trypsin- and amylase-specific activity levels dramatically increased in the middle stages of embryogenesis, whereas at the other embryonic stages the activities of these two digestive enzymes were much lower. Lipase-specific activity exhibited a low level during all embryonic stages. The pattern of digestive enzyme activity was related to organogenesis and the utilization of yolk proteins at different embryonic stages.