ABSTRACT

We investigated the behavioural and oxidative stress responses in the earthworm, Nsukkadrilus mbae on exposure to lead (Pb) and cadmium (Cd) contaminated soils. This was because the response of this species to heavy metals ecotoxicity had not been reported. Two concentrations of Pb (20 and 500 µg/g of soil) and Cd (2 and 10 µg/g of soil) and a control (uncontaminated with Pb or Cd) were used in a completely randomized static non-renewal bioassay design. We found that N. mbae more frequently preferred and burrowed into the control soil than the test soils. Avoidance was more at 500 µg/g Pb (ratio: 1:8) and 10 µg/g Cd (ratio: 1:2). The times to start and to complete burrowing, and the interval between both events were significantly extended in test soils, especially at 500 µg/g Pb and 10 µg/g Cd. Heavy metals contamination elicited increased activity of CAT, SOD and GPx, on short-term (day 2, d-2), and increased synthesis of GSH and MDA on short- and long-term (day 30, d-30) in concentration- and duration-dependent manners. The activity of CAT, SOD and GPx declined significantly on d-30. The heavy metals contamination resulted in both a significant loss in body weight, and mortality. Our preliminary results suggest that N. mbae is a suitable model organism for ecotoxicity studies, because it was able to detect and avoid Pb and Cd contaminated soils, delayed burrowing probably in search of suitable soil patches, and even escaped from heavily contaminated soil.

摘要

我们调查了蚯蚓Nsukkadrilus mbae在暴露于铅 (Pb) 和镉 (Cd) 污染土壤时的行为和氧化应激反应。这是因为尚未报道该物种对重金属生态毒性的反应。在完全随机的静态非更新生物测定设计中使用两种浓度的 Pb（20 和 500 µg/g 土壤）和 Cd（2 和 10 µg/g 土壤）和对照（未受 Pb 或 Cd 污染）。我们发现N. mbae与测试土壤相比，更频繁地优选并钻入对照土壤中。在 500 µg/g Pb（比率：1:8）和 10 µg/g Cd（比率：1:2）时避免更多。在测试土壤中，开始和完成挖洞的时间以及两次事件之间的间隔显着延长，尤其是在 500 µg/g Pb 和 10 µg/g Cd 时。重金属污染在短期内（第 2 天，第 2 天）引起 CAT、SOD 和 GPx 的活性增加，并在短期和长期（第 30 天，第 30 天）浓度中增加 GSH 和 MDA 的合成- 和持续时间相关的方式。CAT、SOD 和 GPx 的活性在第 30 天显着下降。重金属污染导致体重和死亡率显着下降。我们的初步结果表明N. mbae 是生态毒性研究的合适模式生物，因为它能够检测和避免 Pb 和 Cd 污染的土壤，延迟挖洞可能寻找合适的土壤斑块，甚至从严重污染的土壤中逃脱。