Toxicity Of 4-methylbenzylidene Camphor(4-MBC) On Tigriopus Japonicus At Different Salinities

Organic ultraviolet(UV)filters are widely used in personal care products and materials,because of its strong light stability and oxidation resistance.They can effectively avoid the harmful effects caused by UV radiation.In recent years,the continuous expansion of the ozone hole has made the public pay more attention to skin problems,and the demand for the production and use of UV products have also increased.Globally,about 10,000 tons of UV filters are produced per year,and they are still increasing.However,accompanying the human activities,UV filters will eventually enter the aquatic environment.Among them,4-methylbenzylidene camphor(4-MBC)is an organic UV filter which is used frequently.In recent years,4-MBC has been detected in various aquatic media such as rivers,lakes,and oceans.Because of its strong lipophilicity,4-MBC can be easily enriched in biota along the food chains,posing a potential threat to the human.Plently of studies have shown 4-MBC may have adverse effects on biota such as lethal toxicity,developmental toxicity,reproduction toxicity and endocrine disrupting effects.By summaring and analyzing the current toxicity datas of 4-MBC,we found that there is a significant difference between freshwater organisms and marine organisms.The acute toxicity to marine organisms is relatively stronger than to freshwater organisms.Based on this phenomenon,we hypothesize that the difference between freshwater and marine environment may contributes to it.And salinity is a more critical factor.In recent years,people have gradually paid more attention to the effects of salinity on toxicity of environmental pollutants.But researchs had mostly focused on the heavy metals,researchs related to the organic pollutants is scarce.Therefore,we hope to carry out relevant researchs to explore whether salinity may affect the biological toxicity of 4-MBC.It may make great significance for the subsequent researchs on related risks for different ecosystems.In order to investigate whether the change of salinity would affect the toxicity of 4-MBC,we selected the Tigriopus japonicus which has strong salinity adaptability as our experimental organism.By carring out multi-generation toxicity test,we observe the effects of salinity on toxicity on survival,development,and reproduction.In addition,further experiments on bioconcentration were conducted to investigate whether salinity would affect the bioconcentration of 4-MBC and thus leads to differences in toxicity.Finally,the mechanism of salinity affecting 4-MBC toxicity was explored through the determination of the related genes.The main conclusions of our study are as followed:(1)Through multi-generation toxicity test,we have found that salinity can affect the biological toxicity of 4-MBC.Among them,the lethal toxicity and reproductive toxicity of 4-MBC to T.japonicus were enhanced with increasing salinity.There are also differences in toxicity in development.In the 20 and 30 salinity groups,4-MBC may advance the development time.While in the 40 salinity group,the development of T.japonicus was delayed.(2)Salinity may have effects on the physiology of T.japonicus.The increase of salinity may slightly reduce the survival rate and lengthen the development time.The T.japonicus has the highest fecundity in the 30 salinity.Therefore,changes of salinity may influence the toxicity of 4-MBC by affecting the physiology of the T.japonicus.(3)The results of bioconcentration test showed that salinity may affect the bioconcentration of 4-MBC.The 4-MBC maximum concentration,the uptake rate,and the bioconcentration factor all increased with the increase of salinity.Therefore,salinity may affect the bioaccumulation of 4-MBC,which may leads to differences in its toxicity.(4)The expression of oxidative stress related genes and developmental and reproduction related genes in T.japonicus was detected by Quantitative real-time PCR.The results showed that increased salinity significantly up-regulated the expression of oxidative stress related genes,which may be the main reason for the stronger toxicity of the higher salinity group.The differential expression of genes related to development and reproduction,ecr and vtg,may contributes to the differences in toxicity between different salinities.Among them,the expression of ecr and vtg genes in the 4-MBC exposed groups was down-regulated under the highest salinity condition,which may be the main reason for its delayed development and decreased fecundity.