Study Of Different Toxic Effects Of Metalaxyl And Metalaxyl-M On Tubifex Tubifex

Pesticides play an important role in agricultural production,but unscientific and unreasonable application will cause certain harm to ecological safety and human health.Metalaxyl has two enantiomers,due to the lower activity of S-form,the R-form is uesd in practice.However,the ecological risk assessment of metalaxyl only depends on the racemic products.Tubifex tubifex?T.tubifex?,is a freshwater benthic organism in the Oligochaete of aquatic animals,which is widely used in aquatic toxicology and environmental risk assessment.In addition,as one of the most abundant and ubiquitous groups in freshwater ecosystems,T.tubifex is often used as a model organism to assess the bioavailability of contaminants in water because of their special lifestyle.In this study,we evaluated the environmental behaviors of the metalaxyl and metalaxyl-M in T.tubifex.Moreover,the different toxic effects of metalaxyl and metalaxyl-M on T.tubifex physiological indicators and antioxidant enzyme activities were also compared and analyzed.In addition,the high-throughput sequencing technology was applied to obtain the information of the relevant metabolic pathways and biological processes of T.tubifex in the water-cultured system.Finally,we combined the information of the above three aspects to analyze the molecular mechanisms of the differential toxic effects between metalaxyl and metalaxyl-M.The main results were as follows:1. The qualitative and quantitative analysis methods of metalaxyl and metalaxyl-M in T.tubifex,water samples were established.Different T.tubifex culture systems?Metalaxyl/Metalaxyl-M-T.tubifex-Water?were established and applied to investigate the environmental behaviors of metalaxyl and metalaxyl-M in T.tubifex.The results demonstrated that there was no significant difference?p>0.05?of concentration between metalaxyl and metalaxyl-M in T.tubifex at the spiked water exposure process.The dissipation behaviors of metalaxyl and metalaxyl-M in T.tubifex were different?p<0.05?at the non-spiked water culture process.2. The results illustrated that metalaxyl and metalaxyl-M reduced the survival rate(the survival rates of T.tubifex were 63.33±15.28%(20 mg L^-1)?p<0.05?,63.33±5.77%(200 mg L^-1)?p>0.05?treated with metalaxyl and were 50.00±10.00%(20 mg L^-1)?p<0.05?,46.67±11.55%(200 mg L^-1)?p<0.05?treated with metalaxyl-M at the non-spiked water culture process),triggered the autotomy rate?p<0.05?,reduced the biomass?all of four pesticides?treatments at the non-spiked water culture process??p<0.05?of T.tubifex.During the the spiked water exposure process and the non-spiked water culture process,two pesticides?treatments?metalaxyl and metalaxyl-M?inhibited the activities of CAT,SOD,GST and increased the contents of MDA in T.tubifex?p<0.05?.During the non-spiked water culture process,the contents of MDA in T.tubifex treated with metalaxyl-M were significantly increased than those of metalaxyl?p<0.05?.3. GO functional analysis demonstrated that the biological processes related to respiratory chain,actin monomer binding,calcium ion binding were significantly up-regulated for metalaxyl treatment in T.tubifex compared with metalaxyl-M treatment?p<0.05?.KEGG Pathway analysis illustrated that the metabolic pathways associated with human diseases were significantly up-regulates expression for both of the two treatments?p<0.05?.Moreover,compared with metalaxyl-M treatment,metabolic pathways related to human diseases and apoptosis were down-regulated expression?p<0.05?.From the GO functional analysis and KEGG Pathway analysis,the metalaxyl-M had greater influence on the transcriptome of T.tubifex.Part of the results from the transcriptome sequencing analysis can explain the results from the toxic effects.The purpose of the study was to investigate the differential toxic effects of metalaxyl and metalaxyl-M on Tubifex tubifex,combined with the above results obtained from high-throughput transcriptome sequencing so as to illustrate the difference.Our research provided a basis for environmental risk assessment of aquatic organisms and aquatic ecosystems.