Biology Department, Carleton University, Ottawa, Canada.
Biology Department, Acadia University, Wolfville, Canada.
Proc Biol Sci. 2019 Sep 11;286(1910):20191356. doi: 10.1098/rspb.2019.1356. Epub 2019 Sep 4.
Field experiments where parasites are removed through treatment and contaminant levels in host tissues are recorded can provide insight into the combined effects of parasitism and contaminants in wild populations. In 2013 and 2014, we treated northern common eider ducks (Somateria mollissima) arriving at a breeding colony with either a broad-spectrum antihelminthic (PANACUR) or distilled water, and measured their blood lead (Pb) levels. Breeding propensity and clutch sizes were inversely related to Pb in both treatment groups. In comparison, a negative effect of Pb on resight probability the following year was observed only in the anti-parasitic treatment (APT) group. These contrasting patterns suggest a long-term benefit to survival of intestinal parasitism in eiders experiencing Pb exposure. The arrival date of hens explained some, but not all, of the effects of Pb. We weigh the merits of different hypotheses in explaining our results, including protective bioaccumulation of Pb by parasites, condition-linked thresholds to costly reproduction and the direct effects of APT on eider health. We conclude that variation in helminth parasitism influences survival in this migratory bird in counterintuitive ways.
野外实验中，如果通过治疗去除寄生虫并记录宿主组织中的污染物水平，可以深入了解寄生虫和污染物在野生种群中的综合影响。在 2013 年和 2014 年，我们用广谱驱虫药（PANACUR）或蒸馏水治疗到达繁殖地的北方普通潜鸭（Somateria mollissima），并测量它们的血液铅（Pb）水平。在两个治疗组中，繁殖倾向和窝卵数与 Pb 呈负相关。相比之下，只有在驱虫治疗（APT）组中，Pb 对次年重新出现的概率有负面影响。这些对比模式表明，在经历 Pb 暴露的潜鸭中，肠道寄生虫感染对生存具有长期益处。母鸡到达的日期解释了部分而非全部 Pb 影响。我们权衡了不同假设来解释我们的结果，包括寄生虫对 Pb 的保护生物积累、与高成本繁殖相关的条件阈值以及 APT 对潜鸭健康的直接影响。我们得出结论，寄生虫感染的变化以一种违反直觉的方式影响了这种候鸟的生存。
