Response Characteristics Of Behavior And Physiology Of Apostichopus Japonicus To Typical PBDEs Stress

Polybrominated diphenyl ethers（PBDEs）are widely used as flame retardants and are one of emerging pollutants receiving much attention.They are widely distributed in sediments near the Yellow River Delta,Laizhou Bay estuary,and other coastal waters with increased content year by year.Marine ranching located along Laizhou Bay,and it is urgent to monitor and evaluate adverse effects of PBDEs on biological populations in marine ranching.The sea cucumber Apostichopus japonicus,a type of marine benthos,is an important economic species in marine ranching and is used as an indicator of sediment environments.In this study,A.japonicus were exposed to BDE-47,a typical PBDEs detected in Laizhou Bay.Control group and low concentration treatment group(0.1μg·L^-1),medium concentration treatment group(1.0μg·L^-1),and a high concentration treatment group(10.0μg·L^-1)were set to study the accumulation characteristics of BDE-47 in A.japonicus and the effect of BDE-47on the movement,feeding,and respiratory behavior of A.japonicus.Metabonomics techniques were applied to analyze the physiological and metabolic mechanisms of BDE-47 affecting A.japonicus behavior.This study provides theoretical support for constructing an evaluation method for A.japonicus response to BDE-47 stress,and data support for analyzing habitats suitability for A.japonicus aquaculture,controlling water quality standards for aquaculture,monitoring emerging organic pollutants,and constructing marine ranching.The main results are as follows:1.BDE-47 accumulation inlongitudinal striated muscle,intestinal tract,respiratory tree,tentacles,and body wall of A.japonicus in the high concentration treatment group was significantly higher than that in other treatment groups.In addition to muscle tissue,BDE-47 accumulation in tissues in the medium concentration treatment group was also significantly higher than that in the low concentration treatment group.Muscle and respiratory tree are the main tissues accumulated BDE-47 in A.japonicus,and there is a high correlation between BDE-47accumulation and lipid content.2.After 1 day of exposure,compared to the control group,the average and maximum movement rates of A.japonicus in the medium and high concentration treatment groups significantly decreased（P<0.05）.The movement behavior of A.japonicus recovered as exposure time increased.After 10 days of exposure,there was no significant difference of movement behavior among experimental groups,which indicated that A.japonicus’s movement behavior can be adapted to BDE-47.Metabolomic analysis of muscle showed that BDE-47 could significantly change metabolites levels.The significant increase in taurine content and the significant decrease in thyroxine content suggested that BDE-47 may cause inflammatory reactions in the muscle of A.japonicus,which further inhibited neural effects and altered biological behavior.3.Using the method of multi angle photographic recording,the feeding behavior of A.japonicus was studied.BDE-47 had no significant effect on the feeding behavior of A.japonicus.However,metabolomic analysis showed that the contents of 68metabolites significant changed in the intestine of A.japonicus.Among them,the content of taurine decreased significantly,while the content of creatinine increased first and then decreased with the increase of exposure concentration,which indicated that the nutritional level of A.japonicus was affected by BDE-47.Although BDE-47has no significant impact on the feeding behavior of A.japonicus,high concentrations of BDE-47 can induce intestinal inflammatory reactions,alter intestinal absorption capacity,and resulted in the decrease in the nutritional level of A.japonicus.4.BDE-47 had no significant effect on the respiratory behavior of A.japonicus,as no significant changes occurred in the oxygen consumption rate and respiratory frequency of A.japonicus after 20 days of exposure.However,metabolomic analysis showed that the contents of norepinephrine and phenylethylamine in the respiratory tree of A.japonicus changed significantly.These results suggested that A.japonicus protect respiratory function by enhancing neural stimulation under BDE-47 stress,which may alter energy distribution and metabolism.5.The IBR index responded to exposure concentration with specific tissue difference.Moderate concentrations of BDE-47 have a high impact on the muscle,while high and low concentrations of BDE-47 tend to have an impact on the intestinal and the respiratory tree,respectively.IBR index of sea cucumber tissue shows a positive correlation with BDE-47 concentrations,which indicated that serious tissue damage occurred with the increase of exposure concentration.This study showed that the muscle and respiratory tree are the main tissues for the BDE-47 accumulation in sea cucumber,and BDE-47 accumulation is highly correlated with fat content.After 1 day of exposure,compared to the control group,the average and maximum movement rates of sea cucumber in the medium and high concentration treatment groups significantly decreased.However,the movement behavior of sea cucumber adapted to BDE-47.The impact of BDE-47 on the feeding and respiratory characteristics of sea cucumber is relatively small.And BDE-47 can significantly change the metabolic products in various tissues.The tissue damage caused by BDE-47 is more serious as exposure concentration increased.All the results suggested that BDE-47 exposure has a potential impact on the health of sea cucumbers.Metabolites in sea cucumbers can serve as early warning indicators for PBDEs pollution.Continuous monitoring of PBDEs pollution should be carried out in aquaculture areas for sea cucumber.