Effects Of Heavy Metal And Pesticide Exposure On Zebrafish Em Bryo Development

A variety of pollutants in the environment often coexist.Combined pesticide and heavy metal pollution is one of the most common forms of pollution.It is of great theoretical and practical significance to study its influence on environmental organisms.Heavy metals zinc(Zn)and nickel(Ni)are nutrient elements needed by organisms,but they can also have negative impacts on aquatic organisms and ecosystems at excessive concentration.Deltamethrin(DM)is one of the most widely used pyrethroid pesticides.In this study,the effects of single and combined exposure of Zn,Ni and DM were evaluated using zebrafish as a model.The mortality rate,hatching rate,formation rate,heart rate and body length was measured to indicate the toxic effects on zebrafish embryonic development.The transcriptome for single and combined exposures was analyzed to explore the molecular mechanism of toxic affect on zebrafish,screening sensitive molecular markers to indicate the pollutants.The research results are as follows:1.The 168h LC₅₀ of Zn,Ni and DM were 2.79mg/L,7.44mg/L and96.96?g/L,respectively.The mortality of zebrafish increased in a dose-dependent manner after single exposure of Zn,Ni and DM.Zn exposure had an adverse effect on zebrafish hatchability,with a significant decrease at high concentration(4mg/L and 8mg/L)compared with the control group,while Ni and DM exposure had no significant effects on zebrafish hatchability.Exposure to Zn,Ni and DM can cause the developmental malformation of zebrafish.2.The antagonistic effect between Zn and Ni exposure was determined by toxicity unit method.The statistic analysis showed that there may be certain antagonism between Ni and DM exposure.However,the presence of Zn can aggravate the toxicity of DM,and the combined exposure of Zn and DM can significantly inhibit melanogenesis in zebrafish.3.The GO enrichment results of transcriptome sequencing showed that in a single exposure,Zn,Ni had similar influence patterns on the pathway,which was different from DM's influence on the pathway.Heavy metals mainly affect mitochondrial transmembrane transport and adaptive thermogenesis pathways.DM mainly affects DNA damage response,signal transduction by P53 class mediator.In the combined exposures,Ni?DM exposure and Zn?DM exposure were mainly reflected in the pathways of DNA damage response,signal transduction by P53 class mediator and axonal growth cone.Based on gene distribution at KEGG level,it was found that the Zn,Ni,DM,Zn?DM and Ni?DM exposure mainly affected the environmental information processing-signal transduction pathway,while the Zn?Ni exposure mainly affected the environmental information processing-signal molecules and interaction pathway.4.Ten genes related to bone development,cardiovascular development and apoptosis were screened,transcriptome sequencing results and fluorescence quantitative PCR verification results showed that,cyp3a65,cat,sst3,cacng6a and osx were highly sensitive to heavy metal pollution in the exposure group and could be used as candidate molecular markers to indicate heavy metal exposure.