Jensen A, Forbes V E
Department of Life Sciences and Chemistry, Roskilde University, Denmark.
Arch Environ Contam Toxicol. 2001 Feb;40(2):230-5. doi: 10.1007/s002440010167.
The lethal responses of three European clones--A, B, and C-of the prosobranch snail Potamopyrgus antipodarum to acute cadmium exposure were examined by the use of a conventional LC50 test and a delayed toxicity test. The questions addressed were: (1) Are there differences in susceptibility (LC50 values and uniformity of response) among the three European clones of P. antipodarum? (2) Are the patterns of differences in susceptibility among clones observed in the LC50 test also observed for the delayed toxicity test? (3) Is there concordance in the ranking of susceptibility among clones under acute cadmium exposure and under chronic cadmium exposure? The results showed that the widths of the tolerance distribution differed among clones. Clones A and B had a steeper slope than clone C (for clone A the difference was marginally significant), which indicates that individuals from clones A and B showed a more uniform response to acute lethal cadmium stress than individuals from clone C. On the basis of the measured differences in LC50 values, clone A individuals showed the highest tolerance to acute cadmium (LC50 value: 1.92 mg Cd L(-1)) followed by clone B (LC50 value: 1.29 mg Cd L(-1)) and clone C (LC50 value: 0.56 mg Cd L(-1)). Clone C was significantly less tolerant than clones A and B. The delayed toxicity test showed a similar pattern to the LC50 test with regard to tolerance differences among clones; however, mortality continued following transfer to clean water, indicating that cadmium was lethal at much lower concentrations than indicated by the conventional LC50 test. Results of the LC50 test and the delayed toxicity test in the present study were in general agreement with results from chronic cadmium exposure experiments (Jensen et al. [2000] Ecol Appl [submitted]), i.e., the least susceptible clone A in the acute cadmium exposure test was also the least susceptible clone in the chronic cadmium exposure test. Based on the dramatic differences between the LC50 and the cadmium exposure concentrations causing delayed toxicity, we suggest that the potential for delayed toxicity should be given greater consideration in ecotoxicity testing.
通过传统的半数致死浓度（LC50）测试和延迟毒性测试，研究了欧洲三个人类克隆体——A、B和C——的前鳃蜗牛对急性镉暴露的致死反应。研究的问题包括：（1）在欧洲的三种A. antipodarum克隆体中，易感性（LC50值和反应一致性）是否存在差异？（2）在LC50测试中观察到的克隆体之间易感性差异模式，在延迟毒性测试中是否也能观察到？（3）在急性镉暴露和慢性镉暴露下，克隆体之间的易感性排名是否一致？结果表明，不同克隆体的耐受分布宽度存在差异。克隆体A和B的斜率比克隆体C更陡（克隆体A的差异略微显著），这表明克隆体A和B的个体对急性致死镉胁迫的反应比克隆体C的个体更一致。根据测量的LC50值差异，克隆体A的个体对急性镉的耐受性最高（LC50值：1.92 mg Cd L(-1)），其次是克隆体B（LC50值：1.29 mg Cd L(-1)）和克隆体C（LC50值：0.56 mg Cd L(-1)）。克隆体C的耐受性明显低于克隆体A和B。延迟毒性测试在克隆体之间的耐受性差异方面显示出与LC50测试相似的模式；然而，转移到清洁水中后死亡率仍在继续，这表明镉在比传统LC50测试所示浓度低得多的浓度下具有致死性。本研究中LC50测试和延迟毒性测试的结果与慢性镉暴露实验（Jensen等人[2000]Ecol Appl[已提交]）的结果总体一致，即急性镉暴露测试中最不易感的克隆体A在慢性镉暴露测试中也是最不易感的克隆体。基于LC50与导致延迟毒性的镉暴露浓度之间的巨大差异，我们建议在生态毒性测试中应更充分地考虑延迟毒性的可能性。
