| In recent years,the pollution of methidathion in water has aroused people's concern.methidathion is an ideal insecticide,which has good toxicity and good effect.It can be used to control insect pests such as scale insects on most crops.Because of it in agricultural products,in the water,such as not easy decomposition,have been banned in some crops,at present the use of methidathion,though much less,but because of the effects of prevention and control of insect pest shell,there is still a farmers abuse,into the water and cause the destruction of water environment system.This study was to investigate the effects of organophosphorus pesticides-methidathion on the anti-oxidative toxicity of juvenile Oreochromis niloticus.Explores the toxicity of methidathion on tilapia and provides scientific basis for avoiding environmental pollutions of waters,such as oceans,rivers,and ponds.The main findings were as follows:Acute toxicity of methidathion?MD?to nile tilapia.The assessment of the toxicity of nile tilapia exposed to methidathion for 96 h was conducted.The initial weight of nile tilapia were 60g in the experiment.the experiment was divided into 6 experimental concentration gradient groups 0,7.52,10.94,15.83,22.87,33.09(unit:?g L-1),with 3replicates in each group,each placed 10 fish,and the trial lasted 96 h and no feed.The LC50 of 96 h was determined to be:15.83?g L-11 MD,and the no observed effect concentration?NOEC?was 1.75?g L-1,and the lowest observable effect concentration?LOEC?was 6.51?g L-1.The subacute toxicological test was designed for nile tilapia with methidathion concentration of 0.00?N0?,0.80?N1?,1.67?N2?,and 5.34?N3?,7.49?N4?,15.83?N5??gL-1for tilapia.The trial selected initial weight 60±0.5 g,with 3 replicates in each group,each replicated 30 fish,and the trial lasted 12 days and no feed.The results showed that on the 3rd,6th,9th,and 12th days of exposure methidathion,the acetylcholinesterase?AChE?in the liver and serum of nile tilapia was inhibited significantly?P<0.05?,and the activity of AChE was lower with the increase of methidathion concentration.Exposed to MD on the3 day,malondialdehyde?MDA?content was found to be lower in liver tissues of nile tilapia in the N4 and N5 experimental groups than that of in the control group,however,in the experimental group N1,N2 and N3 were increased?P<0.05?,in the serum only N5 group was decreased.On the 6th,9th,and 12th day,the MDA of the experimental group?N5?decreased on the 6th day,while MDA of the other experimental groups was higher than that of the control group in the serum.On the 6th day,9 d,and 12 d,the content of MDA in the liver showed the tendency of inhibition and then increase with the increase of the concentration of MD,while in the serum of the experimental group,the content of MDA decreased only on the 6th day,and showed a tendency of inducing an increase as a whole.The superoxide dismutase?SOD?activity in the liver and serum after 3 days exposure to MD pesticides was significantly higher than that in the control group?P<0.05?,and that was decreased.3th days of exposure to the methidathion pesticides.On the 6th and 9th days,SOD was decreased in the liver,and in seurm the SOD activity of the test N4 and N5 was increased,but with the increase of the concentration of MD,the activity of SOD showed a tendency to increase after the decrease.On the 12th,the test group and the control group the concentration of SOD activity in the liver compared to increase with the increase of MD concentration.The test group N3,serum N4,N5 activity of SOD was higher than the control group,the test group N1,N2 lower than the control group,with the concentration of methidathion increased the activity of SOD showed the first decline after rising the trend.On the 3th days the activity of catalase?CAT?in the N1 and N5 experimental groups was decreased compared with the blank control group,whileN2,N3,and N4 was increased in the liver and serum.On the 6th,9th and 12th day,with the increase of the concentration of methicillin,the CAT activity in the liver first decreased,then rose and then decreased.The activity of CAT in serum decreased first and then increased,and there was a significant difference compared with the control group?P<0.05?.At the same time,with the time of methidathion exposure,the antioxidant enzyme activities of each experimental group showed a nonlinear trend model change.The results of 12 days after exposure to nile tilapia showed that the morphology of hepatocytes was changed and the hepatocytes were necrosis,nucleus pyknosis,edema and degeneration of hepatocytes around the local central vein,and hepatocellular vacuolation appeared with increasing concentration.Simultaneously,eosinophilic masses were found in cytoplasmic osteoporosis.Hemorrhagic deposition was observed locally in the fish bowl,branchial small pieces necrosis and exfoliation,epithelial cells detached from the basement membrane and hypertrophic edema appeared.Results showed that heat shock protein 70?HSP70?,cytochrome C oxidase subunit 7B?COX7B?and cytochrome P450 1B1?CYP1B1?were significantly lower than the control group,PLA2 gene was upregulated,and cytochrome P450 1A?CYP1A?In the concentration?N1,N2,N3,and N4?groups were significantly up-regulated,and the experimental group?N5?was down-regulated;NADPH cytochrome P450 reductase?CYPOR?experimental group N1,N2 were significantly up-regulated,while the experimental group?N3,N4 and N5?had a downward trend compared with the control group.Experimental determination of N0,N2 and N4 group of liver molecular tissue,each group two parallel,six tilapia liver tissue transcriptome analysis showed that in N4 group 76genes were up-regulated and 244 genes were down-regulated compared with N0;In N2group 182 genes were up-regulated and 396 were down-regulated compared with N0.There were 119 genes upregulated and 244 genes down-regulated when N4 was compared with N2.Simultaneously,methidathion caused changes in the morphology of hepatocytes,necrosis of hepatocytes,nucleus pyknosis,and edema of degeneration of hepatocytes around local central veins. |
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