The morphological and histological observation of embryonic development in the oriental river prawn Macrobrachium nipponense

Abstract

In this study,morphological and histological methods were used to observe the embryonic developmental process of the oriental river prawn Macrobrachium nipponense.According to its morphological characteristics,the embryonic developmental process can be devided into eight stages:(a) Fertilized egg,(b) Cleavage stage,(c) Blastula stage,(d) Gastrula stage,(e) Embryonized-nauplius stage,(f) Embryonized-metanauplius stage,(g) Embryonized-protozoea stage,and(h) Embryonized-zoea stage.The cleavage pattern of the oriental river prawn was the transitional pattern between complete cleavage and meroblastic cleavage.The embryo has no blastocoele.Rudiments of the three paired naupliar appendages were organized at the embryonized-nauplius stage.The abdominal region was organized into segments at the embryonized-protozoea stage.Pigments of compound eyes appeared at the embryonized-protozoea stage,and then the pigmental region continued to increase.At the embryonized-zoea stage,structures of the compound eyes reached relative maturity.The segmentation of the abdominal region and the appearance of the pigments indicated that the embryo has been in the embryonized-protozoea stage.The duration of last four embryonic developmental stages were longer than that of other stages,owing to the formation and differentiation of the appendages at later stages.