The Activities Of Four Kinds Of Relative Enzymes In Immune Defense In Early Development Of Mytilus Edulis

The esterase (EST) , peroxidase (POD) , acid phosphatase(ACP) and alkaline phosphatase(AKP)on egg,embryo and early larva of Mytilus edulis were studied by histochemical localization and spectrophotometric method. The aim of the present study was to probe into the immune mechanism in the development process of mollusk's embryo and larva. The EST,POD,ACP and AKP existed in oocyte, embryo or early larva of Mytilus edulis, In different development stages the distributions and activities of EST and POD were different.The histochemical localization results showed that the embryo and trochophore in each development stages from oocyte to D-veliger larva presented EST strong positive reaction and POD positive reaction. The nucleus'colour of Oocyte was lighter than other area. The distribution of EST and POD in a cell were relatively even from 2-cell stage to 32-cell stage. The activities of EST and POD presented difference in different cells since the stage of morula.The defference garadually increased in the stage of gastrula, trochophore larva and D-veliger larva. By histochemical localization, We also found that both of ACP and AKP presented positive reactions in oocyte, fertilized egg, embryo, trochophore and early stage of veliger larva. In oocyte, positive reactions of ACP and AKP presented weaker in the region of nucleus than in cytoplasm; the positive granules in cytoplasm were well-distributed and its size was bigger than in other stages. The positive reaction of ACP in fertilized egg was more intense than in oocyte; the AKP positive reaction granules in the centre region of fertilized egg were more than the surface layer. In cleavage stage, both of ACP and AKP presented intense positive reactions in the region of nucleus, and the positive reaction granules in bigger blastomere were more than in smaller one. In gastrula and trochophore stage, the positive reactions of ACP and AKP presented more intense in the surface layer. In early veliger larva stage, the margin of mantle, visceral mass and basal portion of velum presented intense positive reactions of ACP and AKP. The spectrophotometric method showed that the activity levels ofα- naphthyl acetate esterase were the lowest in oocyte, increasing after fertilization and reached the highest levels in cleavage stage, then gradually decreasing in blastula, gastrula, trochophore and D-veliger larva. The activity ofα- naphthyl butyrate esterase reached the highest level in fertilized egg cells, then gradually decreasing, the lowest levels were in D-veliger larva. The activity levels of halide-independent peroxidase were the lowest in oocyte, increasing after fertilization and reached the highest levels in blastula stage, then gradually decreasing. The variation law of activity levels of halide-dependent peroxidase was similar to halide-independent peroxidase, but the activity was at lower levels in fertilized egg stage than in cleavage stage. ACP and AKP activities were found in oocyte, embryo and early larva by biochemical methods. The enzyme activities of ACP and AKP were at the lowest levels in oocyte than in other stages, and in the following development stages, the enzyme activity levels were increase. The activity levels of ACP grew considerably after fertilization and reached the highest level in blastula stage. AKP activity was at higher levels in cleavage, trochophore and early veliger larva stages, and the highest activity levels were in the early veliger larva.In summary, the EST, POD, ACP and AKP in the embryo and early larva of mussel may play an important role in resisting pathogens in its early stages.