Toxic Effects Of Mercury And Cadmium On Chironomus Kiinensis Larval

Heavy metal of pollutants could make damage to the aquatic ecosystem with the agricultural and industrial polluted water draining,after a long time,heavy metals in the water environment will eventually enter the human body through the food chain,and it will cause the irreversible hazard to the human health.Chironomid can be used as a good indicator organism,its mouthparts of distortion,antioxidant enzymes activity and the pupation rate can be used as biomarkers,and they are applied to warning for the environmental pollutant.In the present study,we used Chironomus kiinensis larvae as a target to study their mouthparts type of distortion,antioxidant enzymes?Superoxide Dismutase;Hydrogen Peroxidase?activity,weight and pupation rate on the chronic and joint toxicity of mercury and cadmium.The detailed results showed as follow.?1? Two kinds of heavy metals will induce Chironomid larvae mouthparts to produce different a degree of deformity.The Hg²⁺ can induce the length of mandibles of Chironomid larvae to increase with the of exposure concentration,and didn't obvious deformity in other parts of mouthparts;after exposure to low concentrations of Cd²⁺,the middle tooth of Chironomid larvae chin are crack;under the joint exposure of Hg²⁺ and Cd²⁺,the Chironomid larvae chin middle tooth and lateral teeth have different degrees of loss,the type of deformity is not related to the concentration of exposure.The results show,heavy metals will induce Chironomid larvae mouthparts to produce a different degree of deformity.Therefore,whether or not the Chironomid larvae mouthparts deformity can be one of a important indexes for evaluation of water environment pollution.?2? After Chironomus kiinensis of 4 instar exposure under different concentration of Hg²⁺,Cd²⁺,and Hg²⁺-Cd²⁺,flush the water to the 4 instar larvae of the Chironomus kiinensis,and dry surface moisture to measure wet weight.Then,after drying to constant weight,the dry weight was measured.We found that the wet weight of larvae increased,the dry weight of Cd²⁺ group was reduced,and the dry weight of other treatments was increased.So,it is not the suitable index for heavy metal pollution monitoring.In the process of Chironomid larvae pupation,the larvae in each treatment group had high sensitivity of Hg²⁺ and Cd²⁺,each treatment group have larvae pupation success,showed inhibitory effect on pupation rate and negative correlation with concentration.Hence,the wet weight and dry weight can be one of the indicators of chronic toxicity.?3? The joint toxic effect of the two kinds of heavy metals is coordination.The antioxidant enzyme's activity of two kinds heavy metals?0.002mg·L-1-0.256mg·L-1?on Chironomus kiinensis larvae showed promote and then inhibitory.Chironomus kiinensis larvae exposure inthe single and the joint toxicity of two kinds of metals,the activity of Superoxide Dismutase?SOD?and Hydrogen Peroxidase?CAT?was cut down with the increase of heavy metal concentration until lower than the control group,and then began to slowly rise to higher than the control group,finally dropped to the lowest value.