Toxic Effect Of Deltamethrin On Schizothorax Prenanti

Pyrethroids are widely used in agriculture,warehousing,and sanitation due to their high efficiency,broad spectrum,and low toxicity to humans.The large use of pesticides such as pyrethroids,inadequate regulatory measures,and incomplete use of pesticides have caused more and more pesticides and their residues to enter the water environment along with rainwater and other routes,causing serious damage to the aquatic ecosystem.Because pyrethroids are lipophilic,residues in the water can easily enter the fish through the larvae of the fish and are transported through the blood circulation of the fish to every tissue and organ of the body,resulting in toxicity.Gills,liver,kidneys,and spleen are the main organs of fish for their functions of respiration,metabolism,and immunity.They are also the main target organs of various types of poisons,damaging the antioxidant system and tissue structure of fish,and affecting various fish species.Physiological functions even lead to death.Therefore,scientific and rational scientific research on the toxicity of pyrethrin pesticides to fish is of great significance to fish breeding,disease prevention and control,protection of polluted aquatic organisms,and standardized use of pesticides.Schizothorax prenanti belongs to Cyprinidae and is a unique cold-water bottom-living fish in China.It mainly lives in mountainous rivers with low water temperature and high dissolved oxygen and has strict requirements on water quality.Any changes of the water environment can cause changes in the physiological and biochemical indicators of the body of the Schizothorax prenanti,which is sensitive to the response of poisons.Therefore,the toxic effects of pyrethroid pesticides were studied,which provided important references for the protection of the wild resources and scientific breeding of Schizothorax prenanti.In this study,deltamethrin in pyrethroid pesticides was selected as the exposure source,and Schizothorax prenanti was used as the test organism for 96h acute toxicity test.Based on a 96h-LC₅₀,the sub-acute toxicity test was performed to observe the histological sections of sputum,liver,kidney,and spleen and measure the activity of SOD?superox ide dismutase?,CAT?Catelas?,GSH-Px?Glutathione peroxidase?and the level of MDA?Malondialdehyde?in the liver,kidney and spleen of Schizothorax prenanti,and then discusse the toxic effects of deltamethrin on Schizothorax prenanti.1.The acute toxicity test of Schizothorax prenantiOn the basis of preliminary experiment,4 concentration gradient treatment groups and 1 blank control group were set up,and the semi-static exposure experiment was performed for 96 h of Schizothorax prenanti.The 96 h-LC₅₀ was 2.5887?g/L calculated by Korbor method.According to the toxicity grading standard,deltamethrin is highly toxic to S.prenanti.In addition,S.prenanti showed extremely high sensitivity to deltamethrin,and in different concentrations exposed to treatment,S.prenanti showed different levels of behavior.2.The effect of deltamethrin on antioxidation systemThe concentration of deltamethrin was designed to 1/16,1/8,1/4,1/2 of 96 h-LC₅₀,which was 0.1618,0.3236,0.6472,1.2944?g/L and 1 blank control group.After exposure for 21d,liver,kidney,and spleen tissues were collected at 1,3,7,14 and 21d after administration.Changes in SOD,CAT,GSH-Px activity,and MDA content were measured using a semi-automatic microplate reader.?1?The results of SOD activity in tissues showed that the activity of SOD in the liver first increased and then decreased,and then increased.In the early stage of exposure?1 d?,the low concentration group?0.3236?g/L?increased SOD activity by 47.66%?P<0.01?.After 3 d,the SOD activity in the high-concentration group?1.2944?g/L?was inhibited and decreased by 19.36%?P<0.01?.After 21 d,SOD activity was induced in the liver,which increased 19.68%?P<0.01?in the high-concentration group.In addition to the low concentration group,the overall SOD activity in the kidneys was induced.The induction effects of the high concentration group at 1,3,7,14 and 21 d were 46.44%?P<0.01?,11.16%?P>0.05?,11.71%?P<0.05?,46.22%?P<0.01?,38.06%?P<0.01?,respectively.The overall performance of SOD activity in the spleen was induced.Among them,the induction was most significant in the low concentration group,and the induction at 1,3,7,14 and 21 d was 116.23%?P<0.01?,94.17%?P<0.01?,46.40%?P<0.01?,49.71%?P<0.01?and 48.01%?P<0.01?,respectively.But the induction was weakened with the prolonged exposure time.?2?The effect of CAT activity in tissues showed that deltamethrin significantly inhibited CAT activity in the liver and kidneys,and the inhibitory effect gradually increase with deltamethrin concentration and exposure time.The inhibitory effects of0.3236?g/L and 1.2944?g/L deltamethrin on liver CAT activity at 21 d were 44.73%?P<0.01?and 66.78%?P<0.01?,respectively.The deltamethrin significantly inhibited CAT activity in the kidney.After 21 d exposure,the inhibitory effects of 0.1618,0.3236,0.6472 and 1.2944?g/L treatment group on the CAT activity in the kidney were 17.74%?P<0.05?,62.88%?P<0.01?,53.81%?P<0.01?,78.03%?P<0.01?.The overall performance of CAT activity in the spleen was firstly inhibited and then induced.The induction effect was weakened,and the CAT activity recovered,which was close to the control group,with the extension of exposure time.?3?The effect of the activity of GSH-Px on tissue showed that deltamethrin inhibited the activity of GSH-Px in tissues as a whole,but as the exposure time prolonged,the inhibitory effect weakened.After exposure for 1,3,7,14 and 21 d,the inhibitory effect of deltamethrin on liver GSH-Px activity was 54.73%?P<0.01?,64.47%?P<0.01?,50.29%?P<0.01?,22.32%?P<0.01?,14.56%?P<0.05?,respectively.The inhibitory effect of GSH-Px activity in the kidney and spleen weakened gradually with the prolonged exposure time,and the GSH-Px activity in the kidney returned to the control level after21 d.The activity of GSH-Px in the spleen increased after 14 d,and the activity increased45.13%?P<0.01?after 21 d.?4?The effect of tissue MDA content showed that the level of MDA in liver,kidney and spleen increased with the increase of exposure time,reaching the maximum at 21d.After exposure for 21 d,the MDA content in the liver,kidney and spleen of the high-dose treatment group increased by 87.73%?P<0.01??67.8%?P<0.01??68.14%?P<0.01?,respectively.3.The effect of deltamethrin on the histopathological damageThe fish was exposed to deltamethrin solutions at concentrations of 0,0.1618,0.3236,0.6472 and 1.2944?g/L.Then the histopathological examination of the gill,liver,kidneys and spleen of Schizothorax prenanti at different exposure times showed that different levels of damage were observed in each tissue.After 7 d and 14 d of exposure,part of the gill filament was distorted and the end of the gill filament was swollen.After exposure for 21 d,the 1.2944?g/L treatment group increased the number of mucus cells in the gill filament,gill filaments enlargement,and the blood vessels dilated and expanded,partial gill filaments loss.After exposure to deltamethrin at a concentration of 0.6472?g/L,the hepatic sinusoids were slightly dilated and congestion.After 7d of exposure to deltamethrin at a concentration of 1.2944?g/L,the hepatic sinusoids were slightly dilated and congestion,and after 21 d exposure,the hepatic sinusoids significantly expanded,the hepatocyte volume was reduced,and the cytoplasm was darkly stained.Deltamethrin did not significantly damage kidney tissue.After 14d of exposure,renal tubular epithelial cells were loosely arranged and the cells were treated with hydropic degeneration.After 21 d exposure,the renal tubular cavity was narrowed,the cells stained lightly,and the glomerulus atrophy was not obvious.After 7 d and 14 d exposuring to deltamethrin at the concentration of 0.6472?g/L,the number of lymphocytes in the lymphoid follicles of the spleen decreased significantly,and cell debris increased.After exposure to 1.2944?g/L deltamethrin for 7 d,the spleen was blood stasis and lymphatic thinning decreased significantly.After 21d exposure,the number of lymphocytes in lymph follicles decreased significantly.Above all,deltamethrin is hypertoxicity to Schizothorax prenanti.With prolonged exposure to low concentrations,deltamethrin can cause damage to the antioxidant system of S.prenanti,and significantly inhibit and induce the activity of SOD,CAT,GSH-Px and the levels of MDA.It can also cause structural damage to gill,liver,kidney and spleen of S.prenanti.