Research On The Biotoxicity Of Butyl Benzyl Phthalate(BBP)to Daphnia Magna

Butyl benzyl phthalate(BBP)is mostly used as a plasticizer to increase the plasticity and flexibility of plastic products.BBP tends to release from the plastic into the environment,even it can enter the food chain.At present,there are few reports on the harmful effects of BBP on freshwater invertebrates.In this study,the growth,reproductive and developmental toxicity(e.g.,survival rate,growth rate,reproduction ability,and the embryonic development)of BBP exposure to Daphnia magna were evaluated,and expression level of vitellogenin(Vg)gene upon BBP exposure was also measured.Meanwhile,the transcriptome exposed to BBP of Daphnia embryo were analyzed.In the 21-day chronic toxicity test,0.1,0.6 and 1.2 mg/L BBP were found to inhibit the survival rate,growth rate and reproductive ability of Daphnia.Interestingly,during continuous exposure to BBP,only the growth rate of 0-7 days was significantly inhibited at the concentration of 1.2 mg/L,but not at other time.The time to first offspring and the total number of offspring per female were significantly decreased in all the treatment groups.Down regulation of Vg gene during BBP exposure was recorded.BBP exposure showed toxicity on embryonic development of Daphnia,resulted in the poorly extended shell spines and the abnormal compound eye.It is worth concerning that exposure to BBP with diverse concentrations predominantly disrupted the developmental process of Daphnia embryo.The total embryonic development time of 1.2 mg/L BBP exposure group decreased by about a third compared to the control group.Based on this finding,we determined the embryo transcriptome of Daphnia under BBP exposure.The results showed that BBP significantly interfere the Daphnia embryos of ribosome biosynthesis and metabolism,protein biosynthesis and metabolism,and transcription process,accelerate the cell cycle and early embryonic development.15 differentially expressed genes(DEGs)were screened by transcriptome analysis,and most of these DEGs involved in Daphnia embryonic cell division,neurogenesis,photoreceptor cell morphogenesis.Our results indicate that BBP could affect the growth and fertility of Daphnia,especially embryonic development of Daphnia.