镉对食蚊鱼(Gambusia affinis)的急性毒性效应

Acute toxicity effects of cadmium on Gambusia affinis

以食蚊鱼(Gambusia affinis)为受试生物,采用半静水式急性毒性试验和亚急性毒性试验,分别测定Cd2+对食蚊鱼的半致死质量浓度(LC50)和超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、谷胱甘肽转硫酶(GST)活性及组织结构变化,检测镉对食蚊鱼的毒性作用,以探讨Cd2+在水环境中的毒性及食蚊鱼在环境科学研究中的应用。结果表明,Cd2+对食蚊鱼96 h的LC50为22.55 mg/L,属于高毒物质。相同Cd2+暴露质量浓度下,随暴露时间延长,SOD和CAT活性总体表现为先升高后降低的趋势,GST活性则总体表现为先升高后降低、且趋于稳定的趋势。Cd2+暴露后食蚊鱼肝和鳃组织会出现不同程度损伤。研究表明,Cd2+对食蚊鱼属于高毒物质,验证了食蚊鱼对化学品Cd2+的敏感性。

To study the effect of cadmium（ Cd） in the water environment and the application of Gambusia affinis in the environmental science,we have conducted acute toxicity tests and sub-acute toxicity tests with Gambusia affinis by using the semi-hydrostatic toxicity testing method. Letting some sorts of fish separately exposed to Cd2 ＋in six different mass concentrations of the median lethal mass concentrations,that is,LC50（ 0,22. 91 mg/L,24. 55 mg / L,26. 30 mg / L,28. 18 mg / L and 30. 27 mg / L）,we have done experiments at three different concentrations of Cd2 ＋（ 1 /4096 h- LC50,1 /20 96 h- LC50,1 /10 96 h- LC50） and a control group（ 0） confected for measuring superoxide dismutase（ SOD）,catalase（ CAT）,glutathione S-transferase（ GST） and the tissue sections of the said fish. The results of our tests indicate that LC50（ 96 h） of Gambusia affinis has been worked out at about 22. 55 mg / L,while LC50 of Gambusia affinis has been detected gradually decreasing with the prolonging of the exposure time. In addition,the activities of SOD,CAT and GST could also be induced at first and then inhibited with the increase of the exposure time at the same exposure concentration. Furthermore,we have also collected the liver and gill of the fish exposed to Cd2 ＋in hoping to find out their pathological variations. In addition,the hepatic lesions in the liver tissues of the fish exposed to Cd2 ＋has been analyzed and characterized by using the hypertrophy of hepatocytes. As a result,we have noticed significant increase of Kupffer cells,circulatory disturbances,focal necrosis,fatty degeneration of hepatocyte at presence of vacuoles,nuclear pycnosis and the narrowing of sinusoids. However,most common gill variations at all doses of Cd2 ＋can be said the desquamation and necrosis. Other related histopathological effects may also include the epithelial hypertrophy,the rising of the lamellar epithelium,oedema,aneurism,epithelial hyperplasia and the fusion of the secondary lamellae.