Study On Endocrine Disruption And Acute Toxicity Of Triclosan To Amphibian Tadpoles

Triclosan(TCS)is broad-spectrum antimicrobial agent used in personal care products,and it has become ubiquitous in the aquatic environment due to wide use.Data show that TCS is toxic to rodents,fish and alga.However,information concerning its toxicity and endocrine disruption is limited.This study aimed to investigate acute toxicity and endocrine disruption of TCS to Pelophylax nigromaculatus tadpoles and Xenopus laevis tadpoles.P.nigromaculatus(Gosner stage 26)and X.laevis(NF stage 46)at the first tadpole developmental stage were exposed to series of concentrations of TCS.Tadpoles were observed and recorded every day,and median lethal concentrations(LC50)for 24 h,48 h,72 h and 96 h were calculated.We found that 96 h-LC50 for TCS to P.nigromaculatus tadpoles and X.laevis tadpoles were 441 ?g·L-1and 280 ?g·L-1,respectively.According to the Test Guidelines on Environmental Safety Assessment for Chemical Pesticides,TCS is highly toxic to P.nigromaculatus tadpoles and X.laevis tadpoles.X.laevis(NF stage 46)at the window tadpole developmental stage were exposed to series of concentrations of TCS(3.6 nM·L-1?36 nM·L-1?360 nM·L-1).We found that TCS result in significantly endocrine disruption to X.laevis.Like normal testes,the gonads with sex-ambiguous morphology exhibited testicular histology,showing that the ex-ambiguous gonads were incomplete ovary-to-testis reversals(IOTTRs)with certain testes morphological features.P.nigromaculatus(NF stage 24)at the window tadpole developmental stage were exposed to series of concentrations of TCS(1 nM·L-1?10 nM·L-1?100 nM·L-1).We found that TCS result in significantly endocrine disruption to P.nigromaculatus.Like normal ovarian,the gonads with sex-ambiguous morphology exhibited testicular histology,showing that the ex-ambiguous gonads were incomplete ovary-to-testis reversals(IOTTRs)with certain ovarian morphological features.To our knowledge,this is the first report strongly demonstrating that triclosan can cause sex reversal in amphibians.Given that the lowest concentration tested is environmentally relevant,our study highlights the risks of triclosan for X.laevis and P.nigromaculatus.