镉在方斑东风螺组织内的蓄积及镉的毒性：水相暴露与食物相暴露比较

为比较直接经水体与经营养传递的2种镉(cadmium,Cd)暴露方式对方斑东风螺(Babylonia areolata)不同组织Cd蓄积和毒性的差异,采用室内模拟法,将螺暴露于含Cd水体(Cd2+:100μg·L-1)或喂食含Cd饵料(牡蛎,34.56μg·g-1以干质量计,先经水体100μg·L-1Cd2+暴露达平衡)30d后再进行15d净化。结果显示,暴露期间,除食物相组螺胃肠道Cd浓度在第10天极显著高于对照组,但随后迅速下降外,其他各组织在2种途径及胃肠道在水相暴露时Cd的浓度均逐渐上升,暴露30d后肝胰脏中Cd浓度最高;净化期,螺鳃中Cd排出率较高,胃肠道与肝胰脏的排出率较低,至净化期末除食物相组鳃中Cd浓度与对照组无显著差异外,2种处理中其他各组织Cd浓度仍显著高于对照组。2种暴露途径中金属硫蛋白(metallothionein,MT)浓度仅在螺肝胰脏中逐渐增加,且与Cd的蓄积呈显著线性正相关。与食物相组相比,水相Cd暴露引起螺肝胰脏脂质过氧化水平(lipid peroxidation,LPO)更高,且内脏团中Cd与其亚细胞成分的金属敏感组分结合的百分比也更高。结果表明,Cd通过营养传递对螺产生的毒性较水体直接暴露低,但摄食是螺蓄积Cd的主要途径;净化后除鳃外水相暴露组螺各组织Cd的排出率较低;因此为了健康养殖与食用安全,东风螺工厂化养成时对饵料与水体Cd浓度的监测均应引起足够的重视。

Toxicity of Cadmium and Its Bioaccumulation in Spotted Babylon, Babylonia areolata: Comparison between Effects of Waterborne and Dietary Exposure

The effects of waterborne and dietary cadmium ( Cd) exposure on bioaccumulation and toxicity in tissues of the Babylonia areolata juveniles were investigated. The snails were exposed to aqueous Cd ( 100 μg·L-1 Cd2+ )directly or fed with Cd pre-exposed oysters ( Saccostrea cucullata ) for 30 d. Cd concentration of the oysters was 34. 56 μg·g-1 ( dry mass) after being exposed to waterborne Cd ( 100 μg·L-1 Cd2+ ) for 14 d,then the snails of the two treatments were depurated for another 15 d. The results indicated that the concentrations of Cd increased with increasing exposure time in all tissues except for the gastrointestinal tract of the dietary group,which decreased gradually after peaked at the 10 th day. The maximal values of Cd accumulated of the two treatments were both in hepatopancreas after 30 d exposure. After depuration,the efflux rates in gill were higher than those in gastrointestinal tract and hepatopancreas. Cd concentrations in different tissues were still significantly higher than that of the control group except for that in gill of the dietary group. The metallothionein ( MT) concentrations of the two treatments increased gradually only in hepatopancreas,which was positively correlated to the amount of the accumulated Cd. Comparedly,the toxicity to the snails after exposure to waterborne Cd was stronger than that after exposure to dietary Cd as more MDA contents produced in hepatopancreas and higher percentages of Cd distribution in metal sensitive fractions of the viscera. The snails accumulated Cd mainly from the diet. The depuration rates of tissues in the aqueous Cd group were lower than those in the dietary Cd group except for that of the gill. Therefore,much attention should be paid to monitor Cd concentrations of the diets and water when the snails were cultured with high-density in factory.