Effects Of Three Environmental Factors On WSSV Proliferation In Procambarus Clarkii

This paper studied the proliferation of WSSV and the activity of hepatopancreatic superoxide dismutase(SOD)in the gill filaments of Procambarus clarkii(Procambarus clarkii)injected with different concentrations of ammonia nitrogen,nitrite and pH in water.,Serum and hepatopancreas catalase(CAT)activity,malondialdehyde(MDA)content,total antioxidant capacity(T-AOC),gill filament Na+-K+-ATPace activity,changes in cumulative mortality for 7 days of stress,the result as follows:First:The effect of different concentrations of ammonia nitrogen on the injection of Procambarus clarkii infected with WSSV.Procambarus clarkii with good viability and no WSSV pathogen was obtained.All crawfish in the experimental group were challenged with WSSV by injection,and all crawfish in the control group were injected with the same dose of PBS buffer.The two groups of crawfish were put into water bodies with ammonia nitrogen concentrations of 0,5,10,15,and 20 mg/L for stress.The water temperature was 24.3±0.5℃,dissolved oxygen was 8.2±0.3 mg/L,and pH was 7.0 Sampling and testing at 24h,48h,72h;repeat the above operation without sampling in the middle,and count the cumulative mortality of crawfish after 7 days of ammonia nitrogen stress;the experiment design 3 parallel.the result shows:Under ammonia nitrogen stress,the higher the ammonia nitrogen concentration and the longer the stress time,the faster the WSSV proliferation in the gill filaments of Procambarus clarkii in the experimental group(p<0.05);the control group did not have cross-infection and did not carry WSSV.Under the stress of ammonia nitrogen,the crayfish in the experimental group did not die in the first three days.From the 4th day of stress,the higher the concentration of ammonia nitrogen,the faster the death of crayfish and the higher the cumulative mortality rate(p<0.05).When the concentration of ammonia nitrogen is 20mg/L,the cumulative mortality rate of Procambarus clarkii reaches 100%per week;However,the control group crayfish did not die within 7 days under ammonia nitrogen stress.Ammonia nitrogen stress can inhibit the antioxidant function of Procambarus clarkii infected with WSSV.Under ammonia nitrogen stress,the experimental group Procambarus clarkii serum CAT activity,serum T-AOC,hepatopancreas SOD activity,hepatopancreas CAT activity,hepatopancreas T-AOC was significantly inhibited(p<0.05).Procambarus clarkii serum MDA content and hepatopancreas MDA content increased significantly(p<0.05),and the higher the ammonia nitrogen concentration,the longer the stress time,the more significant the inhibitory effect(p<0.05);under the stress of ammonia nitrogen in the control group Procambarus clarkii,only high concentration of ammonia nitrogen can significantly inhibit the activity of serum CAT,serum MDA content,serum T-AOC and hepatopancreas T-AOC of Procambarus clarkii(p<0.05).Under ammonia nitrogen stress,the Na+-K+-ATPace activity of crayfish gill filaments in the experimental group was significantly inhibited with the increase of ammonia nitrogen concentration and the prolonged stress time(p<0.05),while the Na+-K+-ATPace activity of crayfish in the control group was basically It does not change with the increase of ammonia nitrogen concentration and prolonged stress time(p>0.05).Experimental results show that ammonia nitrogen stress can promote the proliferation of WSSV in shrimps,inhibit the normal life activities of Procambarus clarkii carrying WSSV,and accelerate the death of Procambarus clarkii.Second:The effects of different concentrations of nitrite stress on Procambarus clarkii injected with WSSV.The experiment method is exactly the same as experiment 1,the water temperature is 24.3±0.5℃,the dissolved oxygen is 8.2±0.3mg/L,the pH is 7.0,the ammonia nitrogen concentration is less than 0.001 mg/L,and the environmental factors are replaced by nitrite and nitrite.The concentrations are:0,2,4,6,8 mg/L,the results show that:Under nitrite stress,the experimental group under high concentration of nitrite stress,as the stress time prolonged,the WSSV proliferation in the gill filaments of Procambarus clarkii was faster(p<0.05);Procambarus clarkii under low concentration of nitrite stress The proliferation of WSSV in vivo was the least,significantly lower than that of the other groups(p<0.05).The control group did not have cross infection and did not carry WSSV.Under nitrite stress,the crayfish in the experimental group did not die in the first 3 days,and died on the 4th day.When the nitrite concentration was 6 mg/L,the 7-day cumulative mortality of crawfish was the lowest(p<0.05),and when the nitrite concentration was 8 mg/L,the 7-day cumulative mortality of crawfish was the highest(p>0.05);However,the control crayfish did not die within one week under nitrite stress.Nitrite can affect the antioxidant function of Procambarus clarkii infected with WSSV,low concentration of nitrite can stimulate the antioxidant function of Procambarus clarkii,and high concentration of nitrite will damage the antioxidant function of crayfish.In the experimental group,under low-concentration nitrite stress,crayfish serum T-AOC,hepatopancreas SOD activity,hepatopancreas CAT activity,hepatopancreas T-AOC increased significantly(p<0.05),serum MDA content,hepatopancreas MDA content The change is not significant(p>0.05);when the nitrite concentration is 0,and under high concentration of nitrite stress,the serum MDA content and hepatopancreas MDA content of Procambarus clarkii are significantly increased(p<0.05),Hepatopancreas SOD activity,hepatopancreas CAT activity,hepatopancreas T-AOC,serum T-AOC were significantly inhibited(p<0.05);with the increase of nitrite concentration,the serum CAT activity of Procambarus clarkii did not change significantly(P>0.05).In the control group,only under the stress of high concentration of nitrite,the activity of CAT in the hepatopancreas of Procambarus clarkii was significantly decreased(p<0.05),and the activity of other antioxidant enzymes did not change significantly(p>0.05).Under the stress of low concentration of nitrite,the activity of Na+-K+-ATPace in the gill filaments of Procambarus clarkii increased first and then decreased,and the final change was not significant(p>0.05).When the concentration of nitrite was 0,it was compared with high concentration of nitrite.Under these two conditions,the activity of Na+-K+-ATPace in the gill filaments of Procambarus clarkii was significantly inhibited(p<0.05);the Na+-K+-ATPace activity in the gill filaments of the control group was only affected by high concentrations of nitrite.Significant inhibition(p<0.05).It can be seen that the specific low concentration of nitrite can stimulate the antioxidant function of Procambarus clarkii infected with WSSV to a certain extent,inhibit the proliferation of WSSV,and reduce the mortality of sick shrimp;high concentration of nitrite can cause the body of crayfish Damage,accelerate the proliferation of WSSV in the crayfish,and increase the mortality of sick shrimp.Third:The influence of different pH on the injection of Procambarus clarkii infected with WSSV.The experiment method is exactly the same as experiment one.The water temperature is 24.3±0.5℃,dissolved oxygen is 8.2±0.3mg/L,pH is 7.0,ammonia nitrogen concentration is less than 0.001mg/L,nitrite concentration is less than 0.001mg/L,and the environment The factors are changed to different pH,and the pH values are respectively:8,7,6,5,4.the result shows:Under low pH stress,the proliferation of WSSV in crawfish increased significantly(p<0.05),and in acidic water,the lower the pH,the faster the proliferation of WSSV;the control group did not have cross-infection and did not carry WSSV.In the experimental group,under different pH stresses,when the pH was 8,the proliferation of WSSV in the gill filaments of Procambarus clarkii was accelerated;in acidic water,the lower the pH,the longer the stress time,and the higher the cumulative mortality(p<0.05);while the control Group crawfish under low pH and slightly high pH stress did not die within one week.Low pH will affect the antioxidant function of crawfish.In the experimental group,under low pH stress,the serum CAT activity,serum T-AOC,hepatopancreas T-AOC,hepatopancreas SOD activity of Procambarus clarkii were significantly inhibited(p<0.05),and the serum MDA content and hepatopancreas MDA content increased significantly(P<0.05),the activity of hepatopancreas CAT increased significantly(p<0.05),and the lower the pH,the more significant the impact;when the pH was 8,the antioxidant enzyme indexes of Procambarus clarkii in the experimental group did not change significantly;control In the group,only when the pH value was below 5,the activity of serum T-AOC and hepatopancreas SOD were significantly inhibited(p<0.05),and the content of MDA in hepatopancreas T-AOC and hepatopancreas significantly increased(p>0.05),There was no significant change in antioxidant enzyme activity indicators(p>0.05).When the water pH is acidic,the gill filament Na+-K+-ATPace activity of the experimental group is significantly reduced(p<0.05),and the difference is not significant under other pH stresses(p>0.05);the control group is under different pH stresses,only when the pH is At 5 and 4,the gill filament Na+-K+-ATPace activity was significantly reduced(p<0.05),and the other pH stress had no significant effect on the crawfish gill filament Na+-K+-ATPace activity(p>0.05).It can be seen that the water pH When the value is slightly higher,the normal life activities of crawfish infected with WSSV are less affected,but the pH is slightly higher,which promotes the proliferation of WSSV to a certain extent and increases the mortality rate;in acidic water,the lower the pH value,the lower the pH value.The more severe the inhibition of shrimp antioxidant function,the faster the proliferation of WSSV and the higher the mortality rate.