Effects of nanometer selenium on immune protection and antioxidant ability of Eriocheir sinensis under hypoxia stress

Hypoxia stress will weaken the immune function and antioxidant capacity of Eriocheir sinensis. In order to reveal the immune protection and anti-oxidation regulation mechanism of nanometer selenium (nano-Se) on E. sinensis under hypoxia stress, we had fed E. sinensis with different doses of nano-Se (0, 0.1, 0.2, 0.4, 0.8 and 1.6 mg·kg⁻¹) in basic diets for 90 d. After the feeding, we conducted a hypoxia stress test and injected Aeromonas hydrophila under hypoxia stress. The results show that: 1) The mortality of E. sinensis under hypoxia stress for 24 h and that infected with A. hydrophila under hypoxia stress reached 62.45% and 100%, respectively. The levels of hemocyanin and the hemocyte count in crab hemolymph, and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in crab tissues increased significantly under hypoxia stress for 12 h (P<0.05), as well as there was a decreasing trend under stress to 24 h. The contents of lactic acid (LD) and malondialdehyde (MDA) continued to rise from 12 to 24 h under hypoxia stress. 2) Appropriate addition amount (0.1−0.4 mg·kg⁻¹) of nano-Se reduced the mortality of E. sinensis significantly and the lethality of A. hydrophila under hypoxia stress (P<0.05), increasing the levels of hemocyanin, the hemocyte count and the activities of antioxidant enzymes (SOD, CAT, GSH-Px) under hypoxia stress significantly, but decreasing the contents of LD and MDA (P<0.05). The addition of 0.8−1.6 mg·kg⁻¹ nano-Se had aggravated hypoxia stress injury. These results indicate that appropriate addition of nano-Se to the diets can improve the decrease of immune response and antioxidant ability of E. sinensis under hypoxia stress, and the optimal dose of nano-Se in basal diets is 0.2 mg·kg⁻¹.