Comparison of water metabolism, antioxidant and immune capacities of juvenile Eriocheir sinensis with different tolerance to air exposure

Air exposure can cause great economic losses to farmers of Eriocheir sinensis. There are some differences in air exposure tolerance among individuals of the same species. In order to study the differences in water metabolism, oxidative stress and immune ability of juvenile E. sinensis with different tolerance to air exposure stress. The crabs were then divided into two groups according to the vigor status, group S with strong tolerance to air exposure and group W with weak tolerance to air exposure. The crabs without air exposure stress were selected as the control group (group C). The differences of water content, water loss rate and weight consumption rate of juvenile E. sinensis during air exposure were compared. The activities of antioxidant enzymes and immune enzymes in hemolymph and hepatopancreas were also compared in the three groups of juvenile crabs. The results showed that: ① The death of crabs appeared at 84 h of air exposure, and all of the crabs were dead at 132 h. The water loss rate and weight consumption rate of the crabs in the group S during the period of air exposure were significantly lower than that in the group W. ② The SOD activities of juvenile E. sinensis in group C and group S were significantly higher than that in group W. The highest CAT activity was found in group C, there was no significant difference in CAT activity between the two air exposure groups of juvenile crabs. T-AOC activity in hemolymph of juvenile crabs in the group W was significantly higher than that in other groups, but the T-AOC activity in hepatopancreas of juvenile crabs in the group W was the lowest. ③The activities of ACP and AKP in the hemolymph of group W crabs were the highest but those in the hepatopancreas were the lowest. The LZM activity in hemolymph of juvenile crabs in two air exposure groups was significantly higher than that in the control group. The LZM activity in the hepatopancreas of the juvenile crabs in group S and W was significantly lower than that in the group C. The results showed that the juvenile crabs with low water loss rate and weight consumption rate had strong air exposure tolerance. Air exposure stress caused oxidative stress and decreased immune ability of juvenile crabs. The SOD, T-AOC, ACP, and LZM activities can be used as important indicators to evaluate the air exposure tolerance of E. sinensis. The results of this study not only help to understand the response mechanism of E. sinensis to air exposure, but also provide a theoretical basis for judging the degree of air exposure stress on the E. sinensis, and provide an effective evaluation index for the screening of the crabs with strong tolerance to air exposure.