Department of Biology, Carleton University, 1125 Colonel By Drive, Raven Road, Ottawa, ON K1A 0H3, Canada.
Wildlife Research Division, National Wildlife Research Centre, Environment and Climate Change Canada, 1125 Colonel By Drive, Raven Road, Ottawa, ON K1A 0H3, Canada.
Sci Total Environ. 2016 May 1;551-552:506-12. doi: 10.1016/j.scitotenv.2016.02.055. Epub 2016 Feb 17.
In many animal species, males and females differ in their levels of contaminants and/or parasitic infections. Most contaminants and gastro-intestinal parasites are obtained through prey ingestion, and thus the causes of sex differences in the distribution of these factors might follow similar pathways. We studied the northern common eider duck (Somateria molissima borealis) as an avian model, and used directed separation path analysis to explore the causes of sex differences in mercury (Hg) and gastro-intestinal helminths. Two trophically transmitted helminths were examined: a cestode (Lateriporus sp.) and an acanthocephalan (Polymorphus sp). We found that the number of Lateriporus sp. varied positively with stable isotope signature (as indicated by δ(15)N in eider breast muscle tissue), and negatively with crustaceans being present in the short term diet. We also found that Polymorphus sp. varied positively with eider tissue stable isotope signature. However, Polymorphus sp. varied negatively with sex indirectly through condition and liver mass. Similarly, Hg concentrations also varied negatively with sex indirectly through condition and liver mass, with both Polymorphus sp. intensity and Hg concentrations significantly higher in males. We found that model fit increased when a negative relationship between the two helminth species was included, suggesting a yet unknown causal mechanism linking these parasites. Our findings suggest that although Hg and gastro-intestinal parasites are both trophically transmitted through the eider's prey items, the factors that contribute towards bioaccumulation of these two burdens differ in source, likely caused by several different factors and may potentially influence each other.
在许多动物物种中，雄性和雌性在污染物和/或寄生虫感染水平上存在差异。大多数污染物和胃肠道寄生虫是通过捕食获得的，因此导致这些因素在分布上存在性别的差异的原因可能遵循相似的途径。我们以北方普通潜鸭（Somateria molissima borealis）为鸟类模型，利用有向分离路径分析来探讨汞（Hg）和胃肠道寄生虫性别差异的原因。我们检查了两种通过食物链传播的寄生虫：一种绦虫（Lateriporus sp.）和一种棘头虫（Polymorphus sp.）。我们发现，Lateriporus sp. 的数量与稳定同位素特征呈正相关（如鸭胸肌组织中的δ（15）N 所示），与短期饮食中存在甲壳类动物呈负相关。我们还发现，Polymorphus sp. 与鸭组织的稳定同位素特征呈正相关。然而，Polymorphus sp. 通过健康状况和肝脏质量间接与性别呈负相关。同样，Hg 浓度也通过健康状况和肝脏质量间接与性别呈负相关，Polymorphus sp. 感染强度和 Hg 浓度在雄性中明显更高。我们发现，当包含两种寄生虫之间的负相关关系时，模型拟合度增加，这表明存在一种未知的因果机制将这些寄生虫联系在一起。我们的研究结果表明，尽管 Hg 和胃肠道寄生虫都是通过潜鸭的猎物通过食物链传播的，但这两种负担的生物积累的因素在来源上有所不同，可能是由多种不同的因素引起的，并且可能相互影响。
