Dietary effect chitosan nanoparticles on growth performance, immunity and resistance against Vibrio splendidus in the sea cucumber Apostichopus japonicas

Abstract

Chitosan nanoparticles (ChNPs)is a linear polysaccharide, which has the potential as a preventive chemical substance to improve the immune function of the body. In this study, chitosan nanoparticles were used as feed additives to investigate the effects of ChNPs on the growth performance, immune indices and resistance against Vibrio splendidus of sea cucumber Apostichopus japonicus. In our study, six groups of sea cucumber were fed for 8 weeks with basal diet and basal diet supplemented with 0.5 % COS, 0.5 % chitosan, 0.5 % ChNPs, 0.1 % ChNPs and 0.02 % ChNPs, respectively. The activities of acid phosphatase (ACP), alkaline phosphatase (ALP), catalase (CAT), superoxide dismutase (SOD) and lysozyme (Lyz) in the coelomic fluid of sea cucumber were detected, together with the relative expression levels of immune gene complement 3 (c3), heat shock protein 70 (hsp70), lysozyme (Lyz) and Toll-like receptor 3 (tlr3). The results showed that the growth performance of sea cucumber which added 0.5 % ChNPs was significantly higher than that of control (P < 0.05). Dietary ChNPs had no significant effect on SOD enzyme activity (P > 0.05), but significantly increased ACP, ALP, Lyz and CAT enzyme activities (P < 0.05). The relative expression levels of c3 and hsp70 genes were significantly increased by any feed additives (P < 0.05). Dietary 0.5 % ChNPs could promote the expression of Lyz gene (P < 0.05), and 0.1 % and 0.02 % ChNPs could inhibit the expression of Lyz gene (P < 0.05). The supplementation of 0.5 % chitosan promoted the expression of tlr3 gene (P < 0.05), while the supplementation of 0.5 % COS, and ChNPs groups inhibited the expression of tlr3 gene (P < 0.05). The challenge test showed that dietary supplementation of 0.5 % COS significant protection to sea cucumber against V. splendidus infection. In conclusion, adding 0.5 % ChNPs could promote the growth of and improve the non-specific immunity.