镉对“标准化”背角无齿蚌的急性毒性及脂质过氧化和DNA损伤的影响

Acute toxicity of cadmium and its effects on lipid peroxidation and DNA damage in “standardized”Anodonta woodiana

为了探究"淡水贝类观察"研究体系的专用指示生物"标准化"背角无齿蚌(Anodonta woodiana)对镉(Cd^(2+))的毒性效应,研究了Cd^(2+)对钩介幼虫(<24 h,平均壳长0.25 mm)、稚蚌(<5 d,平均壳长0.27 mm)和幼蚌(6 months,平均壳长50 mm)的急性毒性,并针对Cd^(2+)积累的靶器官——鳃,分析了幼蚌脂质过氧化产物丙二醛(MDA)、成蚌(48 months,平均壳长85 mm)DNA损伤(OTM)对Cd^(2+)的响应特征。结果表明:Cd^(2+)对钩介幼虫24 h半效应浓度(EC50)为0.001 8 mg·L^(-1),对稚蚌和幼蚌96 h EC50分别为0.004 7、4.5 mg·L^(-1);Cd^(2+)浓度0.05 mg·L^(-1)和0.5 mg·L^(-1)暴露组MDA含量随时间延长呈降低的趋势,MDA含量变化与Cd^(2+)浓度之间不相关(P>0.05);OTM随暴露时间的延长呈升高的趋势,OTM变化和Cd^(2+)浓度之间表现为显著的线性正相关(P<0.05)。研究认为,钩介幼虫和稚蚌有作为Cd^(2+)的灵敏受试物种的潜力,幼蚌和成蚌适于Cd^(2+)污染的监测与评价,OTM可作为Cd^(2+)污染预警的生物标志物。

This study was undertaken to investigate the toxic effect of waterborne Cd2 ＋on the freshwater bivalve ＂standardized＂Anodonta woodiana, a unique bioindicator used in the＂Freshwater Mussel Watch＂project. Glochidia（ 24 h, mean length 0.25 mm）, early juveniles（ 5 days, mean length 0.27 mm）, and late juveniles（6 months, mean length 50 mm）were exposed to various Cd^2＋concentrations for the acute toxicity test. Furthermore, late juveniles or adults（48 months, mean length 85 mm）were used to investigate the temporal variation of lipid peroxidation[malondialdehyde（MDA）content] and DNA damage[Olive tail moment（OTM）] in gills, which are the target organs of Cd^2＋accumulation. The results showed that the 24-h median effect concentration（EC50）for glochidia was 0.001 8 mg·L^-1, whereas the 96-h EC50 values for early and late juveniles were 0.004 7 mg·L^-1and 4.5 mg·L^-1, respectively. MDA content was continuously reduced over time in both the 0.05 mg·L^-1and 0.5 mg·L^-1groups, and was not related to Cd^2＋concentration（P〈0.05）. In contrast, the OTM values increased over time, and were linearly and positively correlated with Cd^2＋concentration（P〈0.05）. These results indicate that glochidia and early juveniles may be used as sensitive test organisms for Cd^2＋toxicology research, late juveniles and adults may be suitable for biomonitoring Cd^2＋pollution, and OTM is a valuable biomarker for early warning of Cd^2＋contamination.