The Toxicity Effect And Mechanism Of Daphnia Magna Under Pravastatin Stress

At present,statins have become increasingly important in the treatment of cardiovascular disease.In addition,statins often are detected in some surface water and effluent from sewage treatment plants,which makes the aquatic ecosystem organisms face the survival predicament and may further cause the potential and lasting harm to the organisms.Therefore,the action mechanism of statins on environmental organisms needs to be solved urgently.Pravastatin（PRA）is a common cardiovascular statin,which is widely used in clinical treatment.As a typical aquatic invertebrate,Daphnia magna（D.magna）is of great significance to the structural stability of the food chain.In addition,D.magna is highly sensitive to poisons,therefore,it was used as the test organisms.In this study,D.magna were cultured in laboratory under clean and pollution-free conditions during 21 days to get the physiological indexes.Secondly,according to OECD guideline 202,in order to provide the basis for further research,acute toxicity test was performed for 48 hours.Then the effects of PRA on physiological conditions of D.magna during 21 days were investigated at macro level.In addition,transcriptomic was used to investigate the effects of PRA on the molecular level of D.magna.Finally,the multigenerational toxicity of PRA on D.magna was investigated.The research results of this paper are as follows:（1）The physiological indexes of D.magna under natural conditions were observed during21 days,including body length,the number of molting and reproduction,individual offspring number per brood and individual total offspring number.In addition,after exposure to different concentrations of PRA,EC₅₀ values of D.magna exposed to PRA was calculated according to the amount of inhibition.The measured 48-hour EC₅₀ of PRA in this study was9.03 mg/L with 95%confidence interval of 8.37 mg/L to 9.82 mg/L.（2）This study evaluated the toxicity of PRA（0,0.5,50,and 5000μg/L）on D.magna during21 days by phenotypic analysis.After 21 days,the body length of D.magna in all PRA treatment groups was significantly reduced,especially the 5000μg/L PRA.The number of offspring increased at 5000μg/L PRA,especially the number of offspring per clutch was higher than that control group.Finally,it was not significant difference in the molting number of D.magna in each PRA exposure group,but there was still a slight increase.（3）The aim of this study was to evaluate the molecular pathway in 21 days on model D.magna at 0,0.5,50 and 5000μg/L PRA by genome-wide transcriptome analysis.After 21 d,D.magna significantly reduced the body length and increased the number of offspring at5000μg/L PRA.The 76,167,and 499 differentially expressed genes（DEGs）were identified by using absolute log2 fold change<1and adj p<0.05 as a cutoff in the 0.5,50,and 5000μg/L PRA treatment groups,respectively.Three pathways including xenobiotic metabolism,insect hormone biosynthesis pathway,and energy metabolism were significantly（p<0.05）enriched after exposure to PRA.These suggested that the upregulation of genes in insect biosynthetic hormone pathway increased the juvenile hormone III content,which further reduced the body length of D.magna.The positive effect of methyl farnesoate synthesis on the ovarian may result in the increased number of offspring.（4）In this study,the toxicity of D.magna exposed to PRA（0,0.5μg/L,50μg/L and 5000μg/L）was investigated using physiological indexes as the criteria for intergeneration toxicity evaluation.The results showed that the body length of D.magna in F1,F2 and F3generations was still inhibited.After 21 the percentage of D.magna（F3）body length inhibition in high concentration test group began to decrease.At the same time,the number of neonates in the high treatment group was still higher than that in control group at F0 and F1,but on the contrary,the number of offspring in the high treatment group was lower than that in the control group at the generations of F2 and F3.In addition,PRA stress caused redness in F1 and F2 generations of D.magna.These results suggested that PRA may still cause significant damage to generational D.magna.