Department Aquatic Ecotoxicology, Institute of Ecology, Evolution and Diversity, Goethe-University, Siesmayerstrasse 70, 60323, Frankfurt am Main, Germany.
Ecotoxicology. 2010 Oct;19(7):1174-82. doi: 10.1007/s10646-010-0501-4. Epub 2010 May 20.
So far only a few studies have been performed to assess the effects of dynamic pollutant exposure on life-history parameters of invertebrates. In a previous multi-generation approach with the midge Chironomus riparius we tested if a chronic tributyltin pre-exposure alters the ability of a population to cope with subsequent cadmium stress. In the experiment two separate chironomid populations were exposed via sediments to different TBT-concentrations (4.46 and 8.93 μg Sn/kg dw) for several generations, followed by subsequent cadmium exposure (1.2 mg Cd/kg dw) for three generations. While the TBT-exposure to 4.46 μg Sn/kg dw had only small effects on the development and reproduction of C. riparius the higher TBT-concentration of 8.93 μg Sn/kg dw led to negative effects on life-history traits. Therefore, a higher adverse effect of the higher TBT-concentration and thus a higher susceptibility to other stressors could be assumed. Within, this paper only the results of the second stressor experiment were presented; clear effects of Cd on development and reproduction of C. riparius were determined independent of the pre-exposure scenario. While no differences in Cd-sensitivity were found between the population without pre-exposure to TBT and the population pre-exposed to the low TBT-concentration (4.46 μg Sn/kg dw), the pre-exposure of midges to the higher TBT-concentration (8.93 μg Sn/kg dw) resulted in a significantly higher susceptibility to subsequent Cd-stress. These results document that the exposure history may influence the reaction to altered chemical stress. Our findings are relevant to understand and predict the evolutionary fate of populations in rapidly changing, human-impacted environments. However, the fact that chemical-induced reduced genetic diversity, which is not necessarily linked to genetic adaptation, leads to a reduced fitness under altered stress conditions, is to our knowledge a novel finding.
到目前为止，只有少数研究评估了动态污染物暴露对无脊椎动物生活史参数的影响。在之前使用摇蚊 Chironomus riparius 的多代研究中，我们测试了慢性三丁基锡预暴露是否会改变一个种群应对随后镉胁迫的能力。在实验中，两个独立的摇蚊种群通过沉积物暴露于不同的 TBT 浓度（4.46 和 8.93μg Sn/kg dw）数代，随后进行了三世代的后续镉暴露（1.2mg Cd/kg dw）。虽然 TBT 暴露浓度为 4.46μg Sn/kg dw 对 C. riparius 的发育和繁殖仅有较小影响，但较高的 TBT 浓度 8.93μg Sn/kg dw 导致对生活史特征产生负面影响。因此，可以假定较高的 TBT 浓度会产生更高的不利影响，从而使种群对其他胁迫物更敏感。在本文中，仅呈现了第二个胁迫物实验的结果；镉对 C. riparius 的发育和繁殖的明显影响独立于预暴露情况。虽然在未预先暴露于 TBT 的种群和低 TBT 浓度（4.46μg Sn/kg dw）预暴露的种群之间没有发现 Cd 敏感性的差异，但摇蚊对较高 TBT 浓度（8.93μg Sn/kg dw）的预暴露导致对随后的 Cd 胁迫的敏感性显著增加。这些结果表明，暴露历史可能会影响对改变的化学胁迫的反应。我们的研究结果对于理解和预测在快速变化的人为影响环境中种群的进化命运具有重要意义。然而，我们认为，化学诱导的遗传多样性降低与遗传适应无关，这会导致在改变的胁迫条件下适应性降低，这是一个新颖的发现。
