Effects of acute nitrogen nitrite stress on non-specific immune response of Apostichopus japonicus"Luhai No.2"
During the development of Apostichopus japonicus industry in China,several challenges have emerged,including decline in germplasm quality,sluggish growth rates,reduced resilience,and fluctuations in salinity during rainy season.Excessive feeding,late clearing of the bottom,and the accumulation of residual bait and excrement caused by limited exchange of aquaculture water can all lead to the production of a large amount of nitrite nitrogen in aquaculture water.A.japonicus"Luhai No.2"was used as materials to study the changes of its non-specific immune indexes under acute nitrite nitrogen stress,and its adaptability to nitrite nitrogen stress was analyzed from the perspective of physiological ecology.It can reveal the physiological mechanism of A.japonicus under actual nitrite nitrogen stress,and provide theoretical basis for improving the key technology of new variety breeding.Nitrite nitrogen concentration was set as 0,4.0,15.8,63.0,251.0,1 000.0 mg·L-1.The contents of acid phosphatase(ACP),alkaline phosphatase(AKP),superoxide dismutase(SOD),catalase(CAT)and malondialdehyde(MDA)in the coelomic fluid of Apostichopus japonicus with different concentrations were determined.It was found that high concentration of nitrite nitrogen had a significant effect on the survival rate of A.japonicus.The mortality rate of A.japonicus"Luhai No.2"increased with the duration of stress.Under different concentration of nitrite nitrogen stress,the activities of ACP,AKP,SOD and CAT in the body fluid of A.japonicus"Luhai No.2"increased first and then decreased.MDA content increased with the increase of nitrite nitrogen concentration and stress time,indicating that A.japonicus was damaged by lipid peroxidation.With the extension of experiment time,the activities of SOD and CAT in coelal fluid of A.japonicus increased within 1-9 h after stress under 4.0 mg·L-1,and then fell back to the level with no significant difference compared with the control group.After 48 h of stress with a nitrite concentration below 63.10 mg·L-1,the activity of immunase in coelomic fluid of A.japonicus increased,but there was no significant difference between it and the control group.It was speculated that the active defense system of A.japonicus was able to maintain the activity of immunase in the body at a normal level under the stress of low concentration of nitrite nitrogen,but the activities of SOD and CAT were inhibited significantly under high concentration of nitrite nitrogen at 1 000.0 mg·L-1.This may be due to the excessive production of reactive oxygen species caused by high concentration stress,which has the risk of oxidative damage to cellular macro molecules.Under high concentration environmental stress,ROS has exceeded the clearance threshold of A.japonicus,resulting in oxidative damage and a significant decline in the activity of antioxidant enzymes.In summary,in the process of promoting the breeding of"Luhai No.2",it is necessary to select an area with suitable environment and adopt reasonable breeding management measures to avoid large accumulation of residual bait and feces in the breeding water environment,and control the concentration of nitrite nitrogen in the breeding water below 4.0 mg·L-1,so as to create a good breeding environment and better expand the yield increase effect of improved varieties.
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