重金属镉对三种潮虫的毒性效应及其回避行为研究

Toxicological Effects of Cd Pollution on Three Species of Woodlouse(Crustacea:Isopoda)and Their Avoidance Behaviors

选择潮虫亚目三种常见种:普通卷甲虫Armadillidium vulgare(Latreille,1804),多霜腊鼠妇Porcellionides pruinosus(Brandt,1833)和中华蒙潮虫Mongoloniscus sinensis(Dollfus,1901)为研究对象,以农田自然土壤为实验土壤,人工添加重金属镉(Cd)进行毒理研究。结果表明:(1)急性毒性试验采取滤纸接触法和自然土壤法开展Cd对三种潮虫的急性毒性试验,三者的半致死浓度(LC50)大小关系为:A.vulgare<P.pruinosus<M.sinensis,说明不同潮虫对Cd的忍耐限度和敏感程度不同。(2)三种潮虫对Cd的富集强弱关系为:M.sinensis>P.pruinosus>A.vulgare。说明陆生等足类能存活于一定浓度的污染土壤中,但不同潮虫对Cd的富集能力不同。(3)三种潮虫对土壤中Cd均表现出明显的回避行为反应,回避能力大小关系为:A.vulgare>P.pruinosus>M.sinensis。与急性毒性试验的测试终点LC50相比,潮虫行为测试终点对土壤中重金属镉的反应更为敏感。根据实验结果,中华蒙潮虫体内Cd的富集量随着Cd浓度的增加呈上升趋势,所以其富集能力和耐受性强于普通卷甲虫和多霜腊鼠妇,在将来有望成为土壤重金属污染生物修复的首选动物类群。

Three commonly observed species of Oniscidea,i.e. Armadillidium vulgare（Latreille,1804）,Porcellionides pruinosus（Brandt,1833）and Mongoloniscus sinensis（Dollfus,1901）in a natural farmland soil,which was amended artificially with Cd for the purpose of exploring toxicological effects of the heavy metal on these woodlice. The exploration covered three aspects,that is,acute toxicity of Cd to woodlice,Cd enrichment in woodlice and avoidance behaviors of the woodlice. The test of acute toxicity of Cd on three woodice was done using the filter paper contact method and natural soil method. It was found with the former,the 48 h half lethal concentration（LC50）of Cd to A. vulgare,M. Sinensis,and P. Pruinosus was 158,448 and 238 μg cm^-2,respectively,while with the latter. The 14 h LC50 of Cd to these woodlice was 2 489,5 048 and 2 616 mg kg^-1,respectively. So in terms of LC50,the three species displayed an order of A. vulgare P. pruinosus M. sinensis,which indicates that the woodlice vary with species in tolerance and sensitivity to Cd. It was also found that acute toxicity of Cd to the woodlice was closely related to duration of the exposure and concentration of Cd and mortality of the woodlice was positively related to concentration of the heavy metal in the soil,that is,morality of woodlice rises with concentration of Cd. Cd is apparently the decisive factor of the toxicological effect in the test and concentration of Cd significantly affects mortality of woodlice（p〈0.01）. The findings suggest that morality of woodlice may be used as an effective and sensitive bioindicator to determine Cd pollution in the soil environment. In terms of Cd enrichment in the woodlice,the three species displayed an order of M. sinensis 〉P. pruinosus 〉A. vulgare,indicating terrestrial isopods can survive in soils polluted with Cd to certain degree and they vary with species in Cd enrichment capacity. In the case of 15 d^-16 mg kg^-1,A. vulgar was the highest in enrichment coefficient,being up to 0.96,in the case of 7 d-48 mg kg^-1,M. sinensis was,reaching 8.37 and in the case of 15 d-48 mg kg^-1,P. pruinosus was,reaching 5.47. Obviously,both M. sinensis and P. pruinosus are capable of enriching Cd,while A. vulgare is not,but just absorbs. Statistical analysis of the enrichment test shows that Cd enrichment in the woodlice is closely related to duration of the exposure or incubation and concentration of the heavy metal. The concentration of Cd effective to cause 80% of A. vulgare to avoid Cd was 32.8 mg kg^-1,with 95% confidence interval being 25.4～42.9 mg kg^-1;the concentration of Cd effective to cause 80% of M. sinensis to avoid Cd was 43.6 mg kg^-1,with 95% confidence interval being 35.9～56.4 mg kg^-1;and the concentration of Cd effective to cause 80% of P. pruinosus to avoid Cd was 40.5 mg kg^-1,with 95% confidence interval being 33.2～52.6 mg kg^-1. Therefore all the three woodlice displayed obvious avoidance behavior in reaction to Cd pollution in the soil. So,in terms of avoiding ability,the three species displayed an order of A. vulgare P. pruinosus M. sinensis. Compared with the endpoint LC50 of the acute toxicity test,the endpoint of the avoidance behavior test was more sensitive to heavy mental Cd in the soil. All the findings in the study show that M. sinensis tends to enrich more Cd when Cd concentration rises in soil and hence is much higher than A. vulgare and P. pruinosus in tolerance and enrichment capacity. It is expected that in future studies, M. sinensis may become the animal group of first choice for use as bioindicator of Cd pollution in soil.