Accumulation And Transformation Of Arsenic In Crayfish Under Different Exposure Conditions

As a harmful pollutant,arsenic has been widely existed in the natural aquatic environment and can accumulate in aquatic species along the food chain.Crayfish is a benthic organism that lives at the bottom of freshwater bodies.Typically,crayfish can accumulate arsenic from water source and diet.Different sources have different transformation mechanisms in different biological tissues.At present,the researches mainly focus on the cumulative conversion of arsenic in a single species such as fish and shellfish in marine water.However,there are few studies on the accumulation and transformation of arsenic along the aquatic food chain and the different arsenic exposure conditions on the accumulation and transformation.As a common food,the cumulative quantity and cumulative forms of arsenic in crayfish tissues may threaten human health.Therefore,in this study,crayfish were cultured in three different arsenic exposures,i.e.,two phases,water phase and food phase.The cumulative quantity and cumulative forms of arsenic in different tissues of crayfish were determined and analyzed.The main conclusions are as follows:(1)Different biological tissues have different accumulate ways and transformation mechanism.For the crayfish.the cumulative rate and cumulative quantity of arsenic in gill,thymus exoskeleton and muscle tissue decrease in turn,and muscle tissue has stronger methylation ability than gill,i.e.,converts inorganic arsenic into organic arsenic.(2)Water phase is the main way for arsenic accumulation.Arsenic accumulation of crayfish exposed to the water phase is much higher than that of food phase.The cumulative quantity of organic arsenic in cravfish by food phase is higher than that water phase,meaning that the detoxification of crayfish by food phase is stronger.(3)In the two-phase culture,it was found that arsenic had a tendency to increase along the food chain in the food chain of water-Hydrilla verticillata-crayfish.(4)Crayfish can reduce As(?)to As(?)and transform inorganic As into DMA and ASB.(5)Only inorganic arsenic ingested by food enters the muscle tissue of crayfish to be completely converted to organic arsenic.Otherwise,it will accumulate in the form of inorganic arsenic in crayfish,which will threaten human health if the crayfish is eaten.