Tocxic Effect Of Benzo(a)Pyrene On Juvenile Apostichopus Japonicus

Benzo pyrene(BaP)is an important organic pollutant of polycyclic aromatic hydrocarbons(PAHs)in the environment.The substance contains two benzene rings in the molecule,the structure is rapid and intense,so it is stablilized and difficult to be degraded.BaP is difficult to lysis in water,but it can dissolve in lipids well.So it is easy to remain in sediments and various organisms for a long time once it enters the Marine environment.This characteristic makes BaP can be enriched with the extension of the food chain,and thus play a role in its strong carcinogenesis,teratogenesis and mutagenicity.At present,it has been selected as one of important biological indicators for environmental monitoring by researchers in the world.In recent years,studies on the toxicity of BaP to aquatic animals have focused on the toxic effects of fish,mollusks and cephalopods.However,the toxicity assessment of environmental pollutants BaP to juvenile sea cucumber Apostichopus japonicus has not been fully assessed.This study through the establishment of polycyclic aromatic hydrocarbon organic pollutants BaP exposed to imitation juvenile sea cucumber stress model,trying to explore benzopyrene exposed to juvenile sea cucumber and intestinal tissue structure,P450 detoxification gene expression,antioxidant enzymes and the influence of the intestinal flora and intestinal health: clarify BaP expose the effects on the young trepang;The negative effects of BaP exposure on intestinal tissue structure and function were further discussed from histology,enzyme activity and gene expression.In our study,the juvenile sea cucumber Apostichopus japonicus were exposed for 14 days in BaP,which is a model polycyclic aromatic hydrocarbon(PAHs),at four different concentrations(0,0.5,5,and 25 ?g/L).The results showed that:(1)The survival rate(SR)of sea cucumbers in the experimental group decreased with the extension of the experiment time.The lowest SR of sea cucumbers in the 0.5 ?g/L BaP group was 89.58% affter 14 th day of the experiment.BaP exposure also significantly affected the growth of young sea cucumbers,and SGR in the BaP group was significantly decrease.(P < 0.05).(2)Histological morphology,it was observed that the intestinal tissue of sea cucumbers in the medium and low concentration of BaP showed swelling,while the intestinal tissue of young cucumbers in the high concentration of BaP showed slight shrinkage.The experimental group were alleviated and recovered after 14 days.(3)P450 gene expression In,The expression of CYP4501A1 was significantly increased in both the high concentration group and the medium concentration group after 7 days and14 days after the experiment.The expression of CYP4502U1 gene was significantly induced in the high-concentration group after 7 days of experiment.The expression of CYP4503A24 gene was significantly decreased in the medium and low concentration groups after 7 days of the experiment,and significantly inhibited in the low and high concentration groups after 14 days of the experiment.The relative expression level of CYP4504V2 gene was significantly decreased in the medium concentration group and significantly induced in the high concentration group at 7 days.After 14 days,there was no statistically significant difference between the concentration groups and the control group.(4)Enzymatic activity and gene expression,BAP exposure resulted in significantly lower ACP activity than control group(P < 0.05),and the activities of AKP and SOD in 1and 7 days of BAP treatment were also significantly lower than control group(P < 0.05).However,the above two enzyme activities recovered after 14 days of BAP treatment,and SOD activity in low concentration BAP treatment group was significantly decrese(P <0.05).(5)At the phylum level,the abundance of P.asperata increased significantly 14 days after BAP exposure,and BAP exposure increased the number of Proteobacteria and Bacteroidetes,while the number of Firmicutes decreased.At the species level,compared with the control group,a variety of beneficial bacteria and indigenous bacteria,such as Lactococcus,Bacillus and Lactobacillus,were reduced in the BAP treatment group.However,bacteria degraded with alkanes were found in the BAP treatment group,including Lutibacter,Pseudoalteromonas,Polaribacter,Rhodopirellula and Blastopirellula.Collectively,these fifindings provide insights into the toxic effects of BaP exposure on A.japonicas associated with intestinal and health.