Effect of food enrichment based on diverse feeding regimes on the immunity of Nibea albiflora by biochemical and RNA-seq analysis of the spleen.

Nibea albiflora is an economically valuable aquaculture species but suffers from various diseases caused by bacteria and parasites. It is necessary to investigate some novel methods to improve the immunity. In this study, three feeding regimes (A: commercial diet; B: 90 % commercial diet+10 % ice-fresh Exopalaemon carinicauda); C: 90 % commercial diet+5 % ice-fresh Exopalaemon carinicauda + 5 % live Perinereis nuntia, named Control group, Group 1 and Group 2 with similar nutrient and energy content were designed to construct the food enrichment model to investigate their effects on the immunity of this species. The study was focused on spleen tissue where biochemical and RNA-seq analysis were performed to reach our goals. The results showed that fish fed the enriched food showed higher immunity than the Control group fish. Food enrichment feeding also could enhance fish adaptive capacity which contributes to enhancing immunity. Compared to the Control group, the diet B feeding enhanced the fish immunity and adaptive capacity by up-regulating important genes like BAX, ITPR3, NOS1, NLRP3 and down-regulating the gene GOT1. Similarly for the diet C feeding, it improved not only fish immunity but also the neurotransmission activity associated with a good physiological condition by up regulating the genes ADCY5, CACNA1C, SMAD4, NOS1 and RXRB. The diet C feeding was the best in improving fish immunity. Above all, our study revealed the positive effects of such a food enrichment model on the fish and provided evidences and data which support the application of the feeding strategies in the healthy culturing of the fish.