Embryonic development of Caridina japonica and in vitro incubation of its fertilized eggs

Abstract:

In this study, Caridina japonica eggs at different developmental stages were incubated in vitro within a self-made incubator. The goal was to provide a reference for research on C. japonica reproductive biology and crustacean embryo in vitro hatching technology. The results showed that C. japonica fertilized eggs took about 25 days to hatch into larvae at a water temperature of 25.5℃ and the developmental accumulated temperature reaches about 637.5℃. The embryonic development went through eight stages: Fertilized eggs, cleavage stage, blastula stage, gastrula stage, embryonized nauplius stage, embryonized metanauplius stage, embryonized protozoea stage, and embryonized zoea stage. The embryos at different developmental stages could hatch to zoea larvae and can develop normally. The maximum in vitro hatching rate was (80.7±2.4)% found in eggs at embryonized zoea stage, which was not significantly different from that observed in normal ovigerous females (79.1±4.9)%. The minimum in vitro hatching rate was (28.2±2.6)%, found in eggs at cleavage stage, which was significantly lower than that of normal ovigerous females. Water temperature had a marked effect on embryonic development using in vitro hatching method. Incubation time gradually decreased with increasing temperature at a range from 15.0℃ to 32.5℃, i.e., where (436.8±124.8) h at 15.0℃, (228.0±88.8) h at 32.5℃. However, the metamorphosis rate from ZⅠ to ZⅡ began to decline when water temperature exceeded 29.0℃.