贻贝(Mytilus edulis)发育早期酸性和碱性磷酸酶活性

ACID AND ALKALINE PHOSPHATASE ACTIVITY IN MUSSEL MYTILUS EDULIS IN EARLY DEVELOPMENT STAGE

采用组织化学和分光光度技术对贻贝卵、胚胎和早期幼虫酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性进行了定位和定量研究,以探讨贝类早期发育过程中的免疫防御机制。组织化学显示,从卵细胞到D型面盘幼虫各个时期都呈ACP和AKP阳性,卵细胞中阳性颗粒较大且分布比较均匀,受精卵中央着色较深,卵裂期核区呈强阳性且大分裂球内阳性颗粒较多,原肠胚和担轮幼虫外层细胞阳性较强,面盘幼虫外套膜边缘膜、内脏团和面盘基部呈强阳性。生化测定ACP和AKP活力,均是卵细胞最低,随着发育酶活力逐步提高,其中ACP活力在受精后和囊胚期明显提高,囊胚期达到最高峰,其后又略有下降;AKP活力在卵裂期、担轮幼虫和面盘幼虫提高较大,面盘幼虫期酶活力最高。ACP和AKP可能在贻贝的发育早期抵抗病原生物侵染方面发挥重要作用。

At present, mollusk immunity for adult animals has been extensively investigated; however, very little is known on the defense mechanisms in early life stages of mollusk. Therefore, acid phosphatase （ACP） and alkaline phos- phatase （AKP） in oocyte, embryo, and early larva of mussel Mytilus edulis were analyzed by histochemical localization and spectrophotometric methods in this study. The histochemical localization results show that both ACP and AKP presented positive reactions in oocyte, fertilized egg, embryo, trochophore, and veliger larva of early stage. However, the reactions were weaker in oocyte, the region of nucleus, than in cytoplasm; the positive granules in cytoplasm distributed evenly in bigger size than those in other stages. The positive reaction of ACP in fertilized egg was more intensive than in oocyte; the AKP positive granules in the central region of fertilized egg were larger than those in the surface layer. In cleavage stage, the region of nucleus presented strong positive ACP and AKP reactions, and the positive granules in blastomere were bigger in size and quantity than those of the other. In gastrula and trochophore, the positive ACP and AKP reactions were strong in the surface layer, and also strong in early veliger larva, the margin of mantle, visceral mass, and basal portion of velum. In addition, the ACP and AKP activities were found in oocyte, embryo and early larva by biochemical methods, in the lowest level in oocyte among all the stages; and during the development stages followed, the enzyme activity levels increased. The activity levels of ACP increased considerably after fertilization, and reached the highest level in the blastula stage. AKP activity was at higher levels in cleavage, trochophore, and early veliger larva stages, highest in the early veliger larva. Therefore, ACP and AKP are active in the early life stages of mussel M. edulis but in significantly different activity levels in different development stages. ACP and AKP may play an important role in preventing pathogens for mussel M. edulis in embryo and early larva stages.