Vidal Dora Elva, Horne Alex John
Southern California Coastal Water Research Project, 7171 Fenwick Lane Westminster, California 92683, USA.
Environ Toxicol Chem. 2003 Sep;22(9):2130-5. doi: 10.1897/02-407.
Resistance to contaminants is an important yet unmeasured factor in sediment toxicity tests. The rate at which mercury resistance develops and its genetic persistence in the oligochaete worm Tubifex tubifex were studied under laboratory conditions. Worms were raised for four generations under two different sediment treatments, one reference clean sediment, the other contaminated with mercury. Worms raised in mercury-contaminated sediment developed mercury tolerance that persisted even when the worms were raised for three subsequent generations in clean sediment. Mercury tolerance was determined by comparative water-only toxicity tests with mercury as the only stressor. Control worms had a mean lethal concentration (LC50) of 0.18 mg/L(-1). Worms exposed to high levels of mercury in sediment had high mercury tolerance with a mean LC50 of 1.40 mg/L(-1). When mercury-tolerant and control mercury-intolerant worms were crossed, their descendants also demonstrated mercury tolerance during lethal toxicity tests. The LC50 for worm descendants resulting from this cross was 1.39 mg/L(-1). Adaptation to mercury exposures occurred rapidly in this group of worms and appears to be due to both phenotypic and genotypic mechanisms. Development of contaminant resistance and adaptation may be common phenomena in aquatic benthic invertebrates, which should be considered during the design and interpretation of toxicity tests.
在沉积物毒性测试中，对污染物的抗性是一个重要但未被测量的因素。在实验室条件下，研究了寡毛纲颤蚓对汞抗性的发展速率及其遗传持续性。在两种不同的沉积物处理条件下，将颤蚓饲养四代，一种是参考清洁沉积物，另一种是被汞污染的沉积物。在汞污染沉积物中饲养的颤蚓产生了汞耐受性，即使在随后三代在清洁沉积物中饲养时，这种耐受性仍然存在。通过以汞作为唯一应激源的仅水相比较毒性试验来确定汞耐受性。对照颤蚓的平均致死浓度（LC50）为0.18 mg/L（-1）。暴露于沉积物中高浓度汞的颤蚓具有高汞耐受性，平均LC50为1.40 mg/L（-1）。当耐汞颤蚓和对照不耐汞颤蚓杂交时，它们的后代在致死毒性试验中也表现出汞耐受性。这种杂交产生的颤蚓后代的LC50为1.39 mg/L（-1）。在这组颤蚓中，对汞暴露的适应迅速发生，似乎是由于表型和基因型机制共同作用。污染物抗性的发展和适应可能是水生底栖无脊椎动物中的常见现象，在毒性测试的设计和解释过程中应予以考虑。
