Histological analysis of Macrobrachium rosenbergii (de Man) eggs incubated in different salinities

Abstract

Macrobrachium rosenbergii is the freshwater shrimp species of greatest economic interest, and its reproduction has been studied for commercial purposes. This study aimed to evaluate the effect of different salinities (0, 6, and 12 mg L-1) on the embryogenesis of this species. The females were observed daily according to their reproductive behavior. Upon the first sign of spawning, when their eggs were attached to the abdomen, they were collected for egg collection and transferred to the incubators at the respectively tested salinities. The eggs were collected every five days for up to 23 days, separated according to their stage of development, histologically processed, and stained for visualization of structural changes during embryogenesis using an optical microscope. From the egg's histological images at different embryonic development stages, the egg hatching time was evaluated, the changes that occurred in the eggs during embryogenesis, the total area of the eggs, the vacuole area, and the ratio between the vacuole area and the total area of the eggs. Differences were observed in hatching time, egg size, and vacuole area and area ratio. The 6 g L-1 of salinity treatment was statistically different from the other in all parameters analyzed. Therefore, it was concluded that 6 g L-1 of salinity positively influenced embryogenesis, as it presented hatches from the 15th day of embryogenesis, demonstrating that there was a greater speed of migration of vitellogenin for the formation of the embryo, accelerating embryogenesis and hatching of M. rosenbergii.