Effects Of 2-Ethylhexyl Diphenyl Phosphate(EHDPP) On Growth,Reproduction And Behavior In Daphnia Magna

2-Ethylhexyl diphenyl phosphate（EHDPP）,one of the typical organophosphate flame retardants（OPFR）,was frequently detected in surface water and biological samples.Up to now,research on the environmental hazards of EHDPP is very limited.Published studies mostly focused on evaluating the toxic effect of EHDPP on higher organisms such as vertebrates,however,the studies on environmental hazards to lower aquatic organisms such as zooplankton were extremely lacking.Therefore,the crustacean zooplankton Daphnia magna（D.magna）was chosen to assess the toxic effect on growth,reproduction and behavior of EHDPP through acute exposure,chronic exposure and multi-generational exposure experiments in this study.Furthermore,related genes expression were examined to explore the possible mechanism.The main results were as follows:（1）The EC₅₀ value of EHDPP for 48 h acute exposure to D.magna was 0.49 mg/L,which suggested EHDPP has high acute toxic effect on D.magna.Based on acute toxicity results and EHDPP contents in natural water,in this experiment,five concentration groups of 0,0.1μg/L,1μg/L,10μg/L,and 10,0μg/L were set to carry out a 21-days chronic exposure experiment.It was found that chronic exposure to 100μg/L EHDPP,the food intake,body length and swimming speed of the D.magnas decreased,the body length of F1 generations decreased and male individuals appeared（P<0.05）.It indicated that EHDPP exposure significantly inhibiteed the growth,behavior,and reproductive levels of D.magna.Gene expression assays found that EHDPP exposure down-regulated the expression of genes those who are related to cell cycle pathways,changed the expression of the juvenile hormone esterase gene jhe,which indicated that EHDPP might lead to cell cycle disturbances and change the level of hormones,and then interfere the normal growth and reproduction of Daphnia manga.（2）Five concentration groups of 0,0.1μg/L,1μg/L,10μg/L,and 100μg/L were selected to carry out continuous multi-generational 21d exposure experiments of F1 and F2 generations,and recovery groups（without EHDPP exposure）were set up for the 21-days recovery experiments of D.magna.It was found that the body length and food intake of F1 generation was decreased,and F2 had a higher proportion of males,indicating that the continuous multi-generational exposure of 100μg/L EHDPP aggravated its effects on the growth and reproduction of the D.magna.In the recovery group,with the prolongation of recovery time,the inhibition of F1 D.magna in body length decreased and male individuals still appeared.Gene expression assays found that after 21 days of recovery,the expression of the juvenile hormone esterase gene jhe was still down-regulated.This suggests that EHDPP exposure-induced reproductive toxicity can cause persistent damage to D.magna.