Two-generation Toxicological Study Of Triphenyl Phosphate(TPhP) In Marine Medaka(Oryzias Melastigma)

Organophosphate esters(OPEs)are widely used as flame retardants in construction materials,electronic equipments,transportation vehicles,furniture and textiles.As Brominated flame retardants(BFRs)are gradually phased out of market worldwide,OPEs are rapidly replacing the usage of BFRs,resulting in a rapid increase of OPEs.OPEs are physically added but not chemically bonded to materials,which can lead to easy release of such compounds into the environment,being a serise emerging pollutants.Triphenyl phosphate(TPhP)is a high production volume OPEs.The high lipophilic property makes TPhP easy to accumulate in the sediment and the biota.The marine environment is an important sink of terrestrial pollutants,more and more studies have reported higher concentrations of TPhP in offshore waters,marine fish and ocean sediments.But so far,toxicological studies on TPhP of marine organisms are limited.Marine medaka(Oryzias melastigma)has become a new marine model species,and is widely used in marine ecotoxicology study due to its small size,short generation cycle,high reproduction rates,sensitive to pollutants and easy maintance.In the present study,the effects of TPhP on the survival,development,reproduction,and metabolism of marine medaka were investigated by sub-chronic exposure and two generations chronic exposure tests.We investigated the mechanism of TPhP toxicity by real-time quantitative polymerase chain reaction(q-PCR).Finally,the ecological risk assessment of TPhP was carried out based on the experimental reported environmental concentrations.The main results are showed as follows:(1)LC50,LOEC and NOEC of TPhP induced sub-chronic lethal toxicity in the 20 days test on marine medaka embryos were 98.3,10 and<10 p.g/L,respectively.The LOEC and NOEC were 5 and<5?g/L in the chronic exposure of the two generations test,and the embryos were more sensitive to TPhP.(2)Two-generation chronic exposure showed that TPhP had significant effects on skeletal/cartilaginous,cardiovascular and liver development and sexual differentiation on marine medaka.TPhP significantly decreased the embryo heart beats.The malformation rates at the 1st fry and adult fish were also induced by TPhP at a dose dependent manner,with the formation of bent pectoral fin and pericardial and yolk sac edema,and spinal curvature as the most frequently observed malformation in the adult fish.In the adults it was found that TPhP exposure affected the sex ratio obviously and the ratio of Female/Male significantly increased with the increasing doses.Consistently,gonadosomatic index(GSI)in the male adult fish decreased,suggesting the estrogenic effects of TPhP.In addition,hepatosomatic index(HSI)showed negative correlation with the concentrations of TPhP.(3)The reproductive test showed that TPhP had significant effects on the fecundity of marine medaka,and reduced cumulative egg production,spawning events and the number of eggs produced by per female.The inhibition of fecundity in F1 generation was more severe than in the FO generation.(4)The metabolism and transformation of TPhP were different between female and male in marine medaka.The BCF of FO generation was 3.88-18.43,and the male had higher BCF than the female.In F1 generation the BCF was 5.25-7.97,which was lower than FO generation.The BCF of the adult liver in FO and F1 generations were 11.57-128.25 and 336.78-516.16,respectively.(5)TPhP exposure induced the expression of Runx-2,BMP2 and BMP4,which might cause abnormal cartilaginous/skeletal development up-regulated.In addition,TPhP induced COX-2 and CYP1A genes up-regulated,resulting in cardiotoxicity.The reproduction-related gene VTG was significantly up-regulated in male liver,suggesting the estrogenic effects of TPhP,which was consistent with the reduced fertility and increase of F/M ratio.(6)A preliminary risk assessment suggested that currently TPhP had no significant risk to marine ecosystems.However,with the rapid increase use of TPhP,the invironmental concentrations may increase,which may increase the risk of TPhP to marine ecosystems.Therefore it was necessary to monitor and assess the risk of TPhP routinely.