Morphological and histological studies on the embryonic development of the freshwater prawn, Macrobrachium rosenbergii (Crustacea, Decapoda)

The present work was carried out to describe the embryonic changes during development of the freshwater prawn Macrobrachium rosenbergii based on some morphological and histological features. In addition the biochemical composition of eggs was investigated during the embryonic development of the studied species. Results revealed that eggs of M. rosenbergii completed their development in 20 days at 28.5 ± 0.45 °C. The present investigation showed that primordial germ cells (PGCs) were detected early in the examined embryos. In 6.5 days old embryo, a cluster of PGCs occupied the dorso-medial region behind the yolky portion. In addition, the biochemical data indicated that the protein content was significantly increased, while lipid and carbohydrate contents decreased during the embryonic development. The lowest water content was found in the bright orange eggs and reached its highest level in the deep brown eggs. It was noted that the increase in the water content was correlated with the increase in the egg diameters. It was also concluded that, variations in the biochemical compositions of eggs reflected changes in their morphogenesis during the embryonic development.