Regulatory role of myo-inositol in the ovarian development of female Chinese mitten crab (Eriocheir sinensis)

The ovarian development of female crab can directly affect the nutritional value, broodstock fertility and health status of offspring and are essential for the success of the crab industry. This study evaluates the influences of dietary myo-inositol (MI) on the ovarian development of female Chinese mitten crab (Eriocheir sinensis). Three diets containing different MI levels (0, 1600 and 3200 mg/kg) were fed to 144 crabs (initial weight: 72.38 ± 2.53 g) for 13 weeks. Crabs fed the diets with 1600, and 3200 mg/kg MI supplementation had significantly higher gonadosomatic index and yolk granule deposition in the ovary than those fed diets without MI supplementation. Crabs fed 1600 and 3200 mg/kg MI supplementation significantly enhanced vitellogenin synthesis in the hepatopancreas, vitellogenin contents in the hemolymph and vitellogenin receptor mRNA level in the ovary compared with those fed diets without MI supplementation. Simultaneously, cyclic adenosine monophosphate content and gene expression of retinoid X receptor, protein kinase A and ecdysteroid receptor in the hepatopancreas, and ecdysteroid content in hemolymph significantly increased when 1600 and 3200 mg/kg MI were supplemented in diets. Moreover, crabs fed 1600 and 3200 mg/kg MI supplementation had significantly higher lipid content in the ovary than those fed the diets without MI supplementation. The neutral lipid content in the hepatopancreas tended to decrease as the dietary MI level increased, while the polar lipid content in the hepatopancreas and the neutral and polar lipid contents in the ovary tended to increase. Dietary MI supplementation significantly enhanced the expression of genes related to lipid catabolism, lipid absorption and transport in the hepatopancreas, and gene expression related to lipid absorption in the ovary, suggesting that MI could promote the transport of lipids to the ovary from the hepatopancreas for ovarian development. This study indicates that dietary 1600 mg/kg MI supplementation is sufficient to promote the ovarian development of E. sinensis.