Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA; School of the Environment, Yale University, New Haven, CT 06520, USA.
Biological Sciences Department, Binghamton University, Binghamton, NY 13902, USA.
Aquat Toxicol. 2023 Aug;261:106626. doi: 10.1016/j.aquatox.2023.106626. Epub 2023 Jul 10.
Ecotoxicological studies using single test populations may miss the inherent variation of natural systems and limit our understanding of how contaminants affect focal species. Though population-level variation in pesticide tolerance is commonly observed in host taxa, few studies have assessed population-level differences in the tolerance of parasites to different contaminants. We investigated population-level variation in insecticide tolerance of three Echinostoma trivolvis life stages (egg, miracidium, and cercaria) to three insecticides (carbaryl, chlorpyrifos, and diazinon). We tested two relevant metrics of insecticide tolerance-baseline and induced-across up to eight different parasite populations per life stage. Across all life stages, the insecticide treatments tended to reduce survival, but the magnitude of their effects often varied significantly among populations. Surprisingly, we found that exposure to chlorpyrifos increased the hatching success of echinostome eggs relative to the control treatment in three of six tested populations. We also found that cercariae shed from snails previously exposed to a sublethal concentration of chlorpyrifos had a significantly lower mortality rate when subsequently exposed to a lethal concentration of chlorpyrifos relative to individuals from snails that were not previously exposed; this suggests inducible tolerance in cercariae. We found no evidence that insecticide tolerance is correlated across parasite life stages within a population. Together the findings of our study demonstrate that single-population toxicity assays may greatly over- or underestimate the effects of pesticides on the survival of free-living parasite stages, insecticide tolerance levels may not be predictable from one parasite life stage to the next, and insecticides can have both expected and counterintuitive effects on non-target taxa.
利用单一试验种群进行的生态毒理学研究可能会忽略自然系统的固有变异性，并限制我们对污染物如何影响焦点物种的理解。尽管在宿主分类群中普遍观察到对杀虫剂耐受性的种群水平变异，但很少有研究评估寄生虫对不同污染物的耐受性的种群水平差异。我们研究了三种棘口吸虫生活阶段（卵、尾蚴和囊蚴）对三种杀虫剂（carbaryl、chlorpyrifos 和 diazinon）的杀虫剂耐受性的种群水平变异。我们测试了两种与杀虫剂耐受性相关的指标-基线和诱导-针对每个生活阶段多达八个不同的寄生虫种群。在所有的生活阶段，杀虫剂处理往往会降低存活率，但它们的影响幅度在不同的种群中往往有很大的差异。令人惊讶的是，我们发现，在六个测试种群中的三个种群中，与对照处理相比，暴露于毒死蜱会增加棘口吸虫卵的孵化成功率。我们还发现，先前暴露于亚致死浓度的毒死蜱的蜗牛释放的尾蚴在随后暴露于致死浓度的毒死蜱时，死亡率明显低于未先前暴露的个体；这表明尾蚴具有诱导耐受性。我们没有发现证据表明，在一个种群内，寄生虫生活阶段的杀虫剂耐受性存在相关性。我们的研究结果表明，单一种群毒性测定可能会极大地高估或低估杀虫剂对自由生活寄生虫阶段存活的影响，杀虫剂耐受性水平可能无法从一个寄生虫生活阶段预测到下一个阶段，杀虫剂可能对非目标类群产生预期和反直觉的影响。
