Studies On Embryonic Development In Freshwater Prawn Macrobrachium Nipponense (Decapoda, Palaemonidae)

This paper mainly studied the process of the embryonic development of Macrobrachium nipponense. Based on the external morphological features of the meroblastic development in living and fixed embryos, this paper is an attempt to establish a staging series for M. nipponense. We defined 8 stages as: Fertilized egg Stage, Cleavage Stage, Blastula Stage, Gastrula stage, Egg-nauplius Stage, Egg-metanauplius Stage, Egg-protozoea Stage, Zoea stage. At the same time, we also determined the variation of their water content, protein content, carbohydrate content and amino acid composition during the embryonic development. The specific activities of four digestive enzymes including pepsin, tryptase, amylase, cellulose were determined by biochemical analysis during the embryonic development of M. nipponense. Three isozymes of lactate dehydrogenase (LDH), malate dehudrogenase (MDH), and esterase (EST) of M nipponense during the embryogenesis were analysed by using technique of polyacrylamide gel electrophoresis.1. The changes of external morphological feature during embryogenesis of M. nipponense.The are no embryonic structures are visible on the surface of the fertilized egg. The yolk mass is granular and dark green. Early segmentation is the total unequal, spiral-cleavage until 32 cell stage, and then it undergoes the superficial cleavage. After 8 times cell divisions, the embryo entering the blastula stage. Some cells from blastoder migrate towards the egg pole, forming the blastoporal area. Some cells in this region undergo shape changes and immigrate to the inner part of the egg, ant then the gastrula stage is beginning. The appendages, pigmented-eyes, heart and other structures and organs came into being in the subsequent stages. The zoea hatched after the egg zoea stage.2. The variation of the major biochemical composition during the embryogenesis of M. nipponense.The present study represents that protein is the main energy sources for theembryonic development of M. nipponense and it also is the important sources for tissue differentiation and organization. The carbohydrate content is one of the sources of the energy and it is also important component that forming the carapace. The total content of amino acids has a decreased trend during the embryogenesis. Of all the amino acids Glu is the highest and very useful to the waste discharge from the embryo. 3. The digestive enzyme activity and isozyme patterns in embryonic development of M. nipponense.The specific activities of four digestive enzymes, which were pepsin, trypsin, amylase and cellulase, were determined by biochemical analysis during the embryonic development of M. nipponense. The results showed that digestive enzymes activities closely correlated with the development in the stages of embryonic development. The activities of pepsin and trypsin show a change of "high-low -high" during the whole embryonic development. The specific activities of cellulase and lipase was lower, While activities of amylase changed as "V", it was the lowest at Egg-nauplius Stage.The patterns of three isozyme systems (LDH, MDH, EST) were investigated with polyacrylamide gel electrophoresis during the embryonic development of M. nipponense. The result showed that the patterns of the isozymes becoming complicated with the embryos developing. The results indicated that the isozyme was necessary during embryonic development and controlled by its genes. They expressed in sequence and cooperated with development for providing construre and energy matters.