| Over the past three decades,the use of pesticides to meet food needs has grown exponentially.Excessive abuse of pesticides inevitably leads to ecological pollution.Reptiles inhabiting these environments have to face the risk of exposure to various pesticides.For a long time,the Pelodiscus sinensis has been an important aquaculture object in China,and its cultivation usually adopts the paddy field polyculture mode,which undoubtedly makes the P.sinensis vulnerable to the threat of pesticides from agricultural activities.Glyphosate,vinclozolin and chlorpyrifos are herbicides,fungicides and insecticides widely used in agricultural activities,respectively.The environmental and ecological impacts of these three pesticides have always been the focus of many researchers,and have been proven to cause harm to a variety of nontarget organisms.However,there is still a lack of information on the potential toxicity of three pesticides exposure to P.sinensis in different periods.Therefore,this study will focus on the effects of glyphosate and vinclozolin on the phenotype,motor performance,gut microbial diversity,and liver metabolism of P.sinensis larvae.In addition,the effects of different concentrations of chlorpyrifos exposure on the embryonic heart rate,hatchling phenotype,exercise performance,red blood cell oxidative stress and liver metabolism of P.sinensis were further investigated.By combining phenotype,physiology,biochemistry and other multi-level evaluation of the toxic effects of three pesticides on Chinese soft-shelled turtle,to provide certain scientific methods and theoretical basis for the protection of reptiles.The main results are as follows:1.There were no significant changes in feeding,growth,swimming speed,gut microbial diversity,and hepatic oxidative stress of P.sinensis during glyphosate exposure.However,in liver metabolism,some metabolites were observed to be significantly different between different treatment groups.These metabolites were mainly involved in amino acid metabolism,glutamate and valine gradually decreased with increasing exposure concentration,and histidine and phenylalanine gradually increased with increasing exposure concentration.In addition,metabolites such as creatinine,creatine,uridine,and choline were significantly different among the different treatment groups.The difference of these metabolites revealed that glyphosate could induce metabolic disorder in the liver tissue of P.sinensis larvae.Based on the environment-relevant concentrations,short-term exposure to glyphosate had only mild toxic effects on larvae of P.sinensis,indicating that P.sinensis were highly tolerant to glyphosate herbicide.2.In the vinclozolin exposure,P.sinensis larvae exposed to high concentrations of vinclozolin(500,5000 μg/L)showed decreased food intake,slow growth and decreased swimming speed.However,vinclozolin at the relevant concentration in the environment had limited effects on the feeding,growth and exercise ability of Chinese soft-shelled turtle larvae.Furthermore,P.sinensis larvae exposed to vinclozolin exhibited gut microbiota dysbiosis,with significant changes in microbial community composition and abundance at different taxonomic levels.Among them,the abundance of Firmicutes decreased with increasing exposure concentration.However,Proteobacteria abundance gradually increased with increasing exposure concentrations.In addition,the abundance of Bacteroidetes was higher in the high concentration group(500 μg/L),but there was no obvious dependence on the exposure dose.Untargeted metabolomic analysis revealed that larvae of P.sinensis exposed to vinclozolin exhibited hepatic metabolic disturbances.These metabolites are mainly involved in amino acid metabolism,energy metabolism and nucleotide metabolism.Among them,some amino acids(threonine,lysine,tyrosine,proline,glutamine)were relatively low at high concentrations of vinyl sclerotium(500,5000 μg/L).The changes of these metabolites indicated that vinclozolin was toxic to the liver of P.sinensis larvae and induced metabolic disorders in the liver tissue.3.In the exposure to chlorpyrifos,it was observed that the embryonic heart rate of the high concentration(200,2000 μg/kg)exposure group increased significantly on the tenth day.However,there were no significant differences in hatching rate and incubation period among different treatment groups.In addition,hatchlings did not differ significantly in body weight,swimming,and oxidative stress in red blood cells.In terms of metabolome,compared with the control group,a higher number of differential metabolites exposed to high concentrations(200,2000 μg/kg)of chlorpyrifos were observed,including some amino acids,ADP,citric acid,stearic acid,ribose 1-phosphate.These differential metabolites were significantly dose-dependent with chlorpyrifos.Among them,the levels of histidine,leucine,cysteine,and citric acid were higher in the high-concentration exposure group(2000 μg/kg),while the levels of ADP,stearic acid,and ribose 1-phosphate were higher in the high-concentration exposure group(2000 μg/kg)levels are relatively low.These metabolite differences revealed that chlorpyrifos exposure induced metabolic disturbances in embryonic liver tissue. |
