Effects Of Flame Retardant Tri(2-Chloroethyl) Phosphate(TCEP) Exposure On Growth,Reproduction,Survival And Gene Transcription Of Daphnia Magna

Organophosphorus flame retardants?OPFRs?are a novel class of environmental contaminants that are frequently detected in a variety of environmental media and in wildlife tissues.Among them,tris?2-chloroethyl?phosphate?TCEP?is the most typical one.According to the relevant literature,the concentration of TCEP in natural water was reported to be up to 1478 ng/L.However,the toxic effects of TCEP on the development and reproduction of aquatic organisms and the mechanism of toxicity remain unclarified.Moreover,the current toxicological studies on TCEP have focused mainly on the partial life stage assessment of the model animals,so that it is easy to underestimate the potential risks to the environment.Therefore,this study aims to explore the effects of acute,chronic and whole-life-stage exposures to TCEP on Daphnia magna?D.magna?development,reproduction,survival and expressions of genes.Hopefully,the result of this research would elucidate the toxic effects and toxicity mechanisms of TCEP,and provide theoretical support for the environmental risk assessment and rational utilization of TCEP.This study mainly drew the following conclusions:1. After 48 h of acute exposure to TCEP,the LC₅₀ of D.magna was 78.05 mg/L.TCEP was one of the more water-soluble OPFRs and was less acute toxicity to D.magna.2. Based on the results of acute toxicity,TCEP with concentrations of 0,1,5,10 mg/L were selected chronic exposure for 21 d.Chronic exposure to TCEP resulted in a significant increase in body length of the F₀ generation D.magna and a significant contribution to their accumulated offsprings,but the average body length of D.magna in the F₁ generation decreased.In addition,the expressions of 155 genes were measured.Among them,the expressions of 73 genes involved in 15 pathways,including metabolism,genetic information processing,cellular processes and environmental information processing,were significant altered.It was indicated that TCEP affected the development and reproduction of D.magna by regulating physiological processes such as protein processing and nutrient absorption and utilization.3. Whole-life-stage exposure to TCEP at concentrations of 0,500,5000 ng/L had significantly effects on D.magna development,reproduction,and survival.Among them,the environmentally relevant concentrations of TCEP promoted the growth of F₀ generation D.magna for a short time?22 d?,and the gene expressions in the pathways related to the developmental and growth stage were correspondingly significantly up-regulated.TCEP also stimulated the D.magna's reproduction to produce more offsprings but shorter body lengths.Finally,environmentally relevant concentrations of TCEP delayed the death of D.magna.During this life stage,the expressions of genes in the two pathways associated with the heart were significantly down-regulated,indicating that TCEP might delay the death of D.magna by protecting their cardiac function for a period of time.