汞和镉对花翅摇蚊(Chironomus kiinensis)幼虫的联合毒性

Joint Toxic Effects of Mercury and Cadmium on Chironomus kiinensis Larval

摘要: 本文选取汞和镉两种重金属，以花翅摇蚊(Chironomus kiinensis)作为研究对象，测定了两种重金属在联合毒性的作用下，对口器畸变，抗氧化酶活性的变化，以及对体重和化蛹率的影响，具体结果如下：1) 在Hg²⁺和Cd²⁺的联合暴露下，可以诱导花翅摇蚊幼虫颏部的中间齿和侧齿均有不同程度的缺失，畸变类型与暴露浓度无关。结果表明，可以将摇蚊幼虫口器畸变的类型作为评价水环境污染的重要指标之一。2) 在不同浓度的亚致死剂量Hg²⁺-Cd²⁺暴露下，各处理组的花翅摇蚊4龄幼虫湿重和干重均增加，不适宜用其作为监测水体重金属污染的指标；花翅摇蚊4龄幼虫化蛹过程中对Hg²⁺和Cd²⁺敏感性高，各处理组均有幼虫完成其化蛹过程，且表现为对化蛹率的抑制作用，与浓度呈负相关关系(P < 0.05)，因此，适宜将其作为慢性毒性效应的指标之一。3) Hg²⁺和Cd²⁺之间的联合毒性表现为协同作用。两种重金属(0.002 mg∙L⁻¹~0.256 mg∙L⁻¹)对花翅摇蚊幼虫体内抗氧化酶活性表现为先促进其酶活性升高，然后抑制其酶活性。花翅摇蚊幼虫在两种金属联合毒性的暴露下，其体内超氧化物歧化酶和过氧化氢酶表现为随着重金属浓度的升高，先快速降低至低于对照组，随后缓慢上升且高于对照组，最后下降至其最低值的变化规律。

Abstract: 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 follows. 1) 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 that heavy metals will induce Chironomid larvae mouthparts to produce a different degree of deformity. Therefore, the Chironomid larvae mouthparts deformity can be one of the important indicators for evaluation of water environment pollution. 2) After Chironomus kiinensis of 4 instar exposure under different concentration of Hg²⁺-Cd²⁺, we found that the wet weight and the dry weight of larvae were 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 had larvae pupation success, and 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. Two heavy metals (0.002 mg∙L⁻¹ - 0.256 mg∙L⁻¹) promote the activity of antioxidant enzymes in Chironomidae larvae, and then inhibit the activity of antioxidant enzymes. With the Chironomus kiinensis larvae exposure in 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 being lower than the control group, and then began to slowly rise to higher than the control group, finally dropped to the lowest value.