Effects of salinity on reproductive characteristics and embryo quality of Eriocheir sinensis

Salinity is a limiting factor affecting gonadal development, mating, oviposition, growth and breeding of Eriocheir sinensis. In the research on the reproductive performance and embryo quality of E. sinensis, the existing reports mainly focus on the effects of different populations, parental specifications and bait composition,while the effects of salinity on the reproductive characteristics and embryo quality of E. sinensis have not been examined. In order to find out the effects of salinity on the reproductive characteristics and embryo quality of E. sinensis parents, the reproductive and oviposition experiments of parents under different salinities (3, 6, 9, 12, 15, 18, 21) were set up. The reproductive characteristics of parents, such as egg production, reproductive index and fecundity, and the egg diameter, weight, biochemical composition and fatty acid composition of embryos were analyzed. The results showed the following. ① The lowest salinity for spawning was 6, at the range of salinity 6-21, the egg production, reproductive index and fecundity of E. sinensis parents increased first and then decreased. When the salinity was 18, the egg production, reproductive index and fecundity of the parents were the highest, and there were significant differences with other groups (P<0.05). ② The embryo diameter was the largest at salinity 6, with an average of (391.13±12.27) µm, which was significantly higher than that in other groups (P<0.05). When the salinity was 12, the wet weight and dry weight of single embryo were the highest, which were (50.64±2.80) µg and (14.85±0.31) µg respectively, and there were significant differences with other groups (P<0.05). ③ With the increase of salinity, the contents of crude protein, total lipid and moisture in the embryo of E.sinensis increased at first and then decreased. When the salinity was 15, the contents of crude protein, total lipid and ash in embryos reached the highest, with an average of (20.64%±3.42%), (8.65%±1.44%) and (1.30%±0.22%) respectively. There was no significant difference in moisturecontent under different salinities (P>0.05). With the increase of salinity, the contents of cholesterol and phospholipid in embryos increased first and then decreased, while the contents of triglyceride did not change significantly. ④ A total of 19 kinds of fatty acids were detected in the embryos of E. sinensis, including 7 kinds of saturated fatty acids, 4 kinds of monounsaturated fatty acids and 8 kinds of polyunsaturated fatty acids. At salinity 6, the contents of C20:4n6 (ARA), C20:5n3 (EPA) and C22:6n3 (DHA) in embryos were the highest, averaging at (0.0098%± 0.0011%), (0.4300%±0.0044%) and (0.0652%±0.0008%), respectively, which were significantly higher than other groups (P<0.05). At salinity 21, the total contents of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) were the highest, and there were significant differences with other groups (P<0.05). Salinity had a certain effect on the quality of embryos, reproductive characteristics of E. sinensis were the best at salinity 18. This experiment explored the relationship between salinity and the reproductive characteristics and embryo quality of E. sinensis, in order to further provide basic dataand reference for the breeding of E. sinensis, and provide theoretical basis and scientific support for seeding production.