Abstract:Selenium is an important trace element to maintain the normal physiological function of an organism. It plays important roles in regulating the balance of redox environment and improving the immunity. Appropriate amount of exogenous selenium can enhance the immune function of aquatic animals, improve ability to resist disease, and rich selenium content in aquatic product. In current study, juvenile sea cucumber (Apostichopus japonicus), with body weight of (60.75±0.32) g, were cultured in tanks of each 150 cm × 120 cm × 60 cm for 4 weeks with water temperature of 16-18℃. They were fed diets containing selenium-enriched yeast at the dose of 0, 0.20 mg/kg, 0.40 mg/kg, 0.80 mg/kg, 1.60 mg/kg, 3.20 mg/kg and 6.40 mg/kg. Survival rate was determined and different enzyme activities were assayed in order to evaluate the influence of different levels of selenium inclusion on biological indices related to growth, digestion and immunity. Selenium enrichment was detected by hydride generation-atomic fluorescence spectrometry (HG-AFS) in sea cucumber. The results showed that the survival of sea cucumber (up to 100%) and activities of digestive and immune enzymes were improved by appropriate concentration of selenium supplementation with the maximum activities of protease (35.13 U/mg prot) and amylase (0.51 U/mg prot), 2.45 and 2.07 times higher than the control group. The maximum activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), alkaline phosphatase (AKP) and acid phosphatase (ACP) were observed in the group fed the diet containing selenium concentration of 0.80-1.60 mg/kg diet, and they were significantly higher than those in the other groups. Furthermore, selenium contents in the sea cucumber tissues were increased at different levels. The organic selenium concentration was several times higher than inorganic selenium, indicating that enrichment of organic selenium is the main way into the body. In conclusion, the diet of selenium concentration from 0.80 mg/kg to 1.60 mg/kg fed in sea cucumber was the most appropriate amount. This study enriches the nutrition research of sea cucumber and provides a frame reference for sea cucumber’s healthy, efficient and sustainable breeding.
