Influences of dietary vitamin D on growth, antioxidant capacity, immunity and molting of Chinese mitten crab (Eriocheir sinensis) larvae.

This study investigates the effects of vitamin D (VD) on growth performance, antioxidant capacity, immunity and molting of larval Chinese mitten crab Eriocheir sinensis. A total of 6,000 larvae (7.52 ± 0.10 mg) were fed with six isonitrogenous and isolipidic experimental diets with different levels of dietary VD (0, 3000, 6000, 9000, 12000 and 36000 IU/kg) respectively for 23 days. The highest survival and molting frequency were found in crabs fed 6000 IU/kg VD. Weight gain, specific growth rate, and carapace growth significantly increased in crabs fed 3000 and 6000 IU/kg VD compared to the control. Broken-line analysis of molting frequency, weight gain and specific growth rate against dietary VD levels indicates that the optimal VD requirement for larval crabs is 4825-5918 IU/kg. The highest whole-body VD content occurred in the 12000 IU/kg VD group, and the 25-dihydroxy VD content decreased with the increase of dietary VD. The malonaldehyde content was lower than the control. Moreover, the superoxide dismutase activity, glutathione peroxidase and total antioxidant capacity of crab fed 6000 IU/kg VD were significantly higher than in control. Crabs fed 9000 IU/kg showed the highest survival after 120 h of salinity stress, and the relative mRNA expressions indicate vitamin D receptor (VDR) is the important regulatory element in molting and innate immunity. The molting-related gene expressions showed that the response of crab to salinity was self-protective. This study would contribute to a new understanding of the molecular basis underlying molting and innate immunity regulation by vitamin D in E. sinensis.