Effects evaluation of in vitro incubation and maternal incubation of Procambarus clarkii embryos

The aquaculture of Procambarus clarkii has developed rapidly nationwide in recent years. According to statistics, the production of P. clarkii in 2021 reached 2 633 600 tons, become the most highly-produced freshwater crustaceans in China. However, limited knowledge about intensive breeding of P. clarkii seedlings has hindered its sustainable development. Artificial incubation may be an effective way to realize intensive breeding of P. clarkii seedlings. The mortality, hatching rate and embryo development of P. clarkii embryos were compared between in vitro incubation mode and maternal incubation mode to evaluate the feasibility of in vitro incubation of P. clarkii embryos and explore its artificial intensive incubation techniques. The results showed that the mortality of embryos at different incubation periods (2-4 days, 5-7 days, 8-10 days, 11-13 days of the experiment) were significantly different. Embryos mortality in the prepared hatching stage (11-13 days of the experiment) was significantly higher than that in 2-4 days and 8-10 days, but there were no significant differences in total embryos mortality between the two incubation treatments. At the same measurement time, the developmental stages of embryos of two incubation treatments were similar and there were no embryo morphological abnormalities. However, embryos hatched under in vitro incubation were susceptible to mycelial attachment, and the dead embryos of in vitro incubation were all infected by the mycelium. Two incubation treatments appeared the first instar larvae at the same time. The hatching rate of embryos of in vitro incubation was significantly lower than that of maternal incubation. But a higher hatching rate (76.91%±4.62%) of embryos under in vitro incubation was obtained. The study indicated that the feasibility of P. clarkii embryos under in vitro incubation was good. The main problem of embryos under in vitro incubation was the embryonic death due to the oomycete infection. In order to reduce the mortality of embryos under in vitro incubation, gradient anti-oomycete could be carried out.