Effect of immunity-stimulants on immunity function of Eriocheir sinensis

The indices of non-specific immunity of freshwater crab,Eriocheir sinensis,injected or fed with laminarin(A), Aeromonas hydrophila bacterin (B) and chitosan (C) were measured. After the 48 h of post-injecting, lysozyme activities of three experimental groups (A, B, and C) were 0.185, 0.234 and 0.233, respectively, while the control group (D) was 0.094. There were no significant differences between experimental and the control group by using t test. SOD activities of three experimental groups were 283.2, 263.5 and 289.8, respectively, while the control group was 120.15. There were highly significant differences between A and D, and B and D, but there was no significant difference between C and D. These results indicated that the three immunity-stimulants might significantly elevate the non-specific immunity of crab. After the 9 days of post-feeding with medicated diet, the lysozyme activities of experimental group were higher than those of the control group. There was highly significant difference between experimental group and the control group by using t-test. The SOD activities of experimental group were also higher than those of the control group. There was highly significant difference between E group and the control group (D), whereas there were significant differences between F and the control group, and G group and the control group. The crab fed by immunity-stimulants could significantly increase the non-specific immunity of crab. The chitosan used in the fields could efficiently prevent the occurrence of crab disease and increased the survival rate of crab by 10% compared with the control group.