Morphogenesis and variations in biochemical composition of the eggs of Macrobrachium nipponense (De Haan, 1849) (Decapoda, Caridea, Palaemonidae) during embryonic development

Morphogenesis and variations in biochemical composition of the eggs of the prawn, Macrobrachium nipponense were studied during embryonic development. Eight morphological stages were defined. These are: the fertilized egg, cleavage, blastula, gastrula, egg-nauplius, egg-metanauplius, protozoea, and zoea. The whole embryogenesis lasts about 25 days at a water temperature of 18-22°C. Proteins, lipids, and carbohydrates were the main components of the embryos. During early embryonic development, protein content generally increased while the contents of lipid and carbohydrate decreased. It is suggested that the proteins in the yolk were used mainly in structural growth, whereas the lipids and carbohydrates were mainly used as energy sources. Lipid content increased while protein content decreased in the protozoea stage, showing that lipid is an important structural substance and protein can be utilized as an energy source, especially in late embryonic stages. Variations in biochemical composition were closely related to events in morphogenesis during embryonic development. The embryonic developmental stages used in the present study may be applied to other embryonic developmental studies of Macrobrachium, and be applicable in other palaemonids as well.