As a micronutrient, vitamin C plays an important role in growth and immunity of fish, but the effects of vitamin C on Pampus argenteus were still unclear. Here, we added vitamin C with different concentrations (0, 350, 1050, 2100 and 4200 mg/kg) to the basic diet, and the optimal concentration of vitamin C was screened out as 1050 mg/ kg through the growth indicators, antioxidant enzyme activities (SOD, CAT, GSH-PX and MDA) and the expression of four immune-related genes (IL-2, IL-3, IL-17 and IL-18). After feeding dietary vitamin C supplementation with optimal concentration for 4 weeks, 80 ml/t formaldehyde was used to damage the immune system of fish. Then, the activities of the antioxidant enzymes and immune-related genes were tested to find out the protective effects of vitamin C on the immune system. The results showed that the activity of CAT, SOD and GSH-PX increased, while the MDA content decreased. At the molecular level, the expression of IL-2 and IL-3 genes increased, but the expression of IL-17 and IL-18 genes was inhibited. These findings suggested that the dietary vitamin C supplementation improved fish growth, alleviated the stress reaction caused by formaldehyde treatment and improved the immunity of P. argenteus.
Present broodstocks of large yellow croaker are borne from extremely small numbers of base population. Thus, it is necessary to analyze kinship of broodstocks in order to avoid inbreeding that will bring out the reduction of individual survival and growth. This paper reports kinship reconstruction and genetic diversity in 103 broodstocks of large yellow croaker by utilizing 23 microsatellite markers. Genetic diversities of 103 croakers at 23 loci pronounce that there are 134 alleles in total and an average of 5.82, and the observed average heterozygosity of 0.599 3, demonstrating that these broodstocks still maintain genetic variability to some extent. The results of sibling groups reconstructed are not identical using two methods of Likelihood and 2-allele recombinatorial optimization. However, the evidence of close relationship between broodstocks is confirmed. The mating combinations are compared between these two methods, as a result of 85% identity and a final selection of 2-allele method. This study aims at finding a better way to avoid inbreeding occurred in broodstocks, and facilitating the aquaculture market of large yellow croaker, meanwhile, offering methods and statistical models to artificial propagation in other marine fish species.
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