Sources of variation in endohelminth parasitism of common eiders over-wintering in the Canadian Arctic

Documenting how climate change will affect Arctic ecosystems and food web dynamics requires an understanding of current sources of variation in species distributions, frequency, and abundance. Host–parasite interactions are expected to be altered in the coming decades under warming conditions. However, in many Polar Regions, there is little information describing parasite–host assemblages. We examine how gastrointestinal helminths of northern common eider ducks ( Somateria mollissima sedentaria ) in the low Arctic vary with host age, sex and sampling year. We found that the prevalence of an acanthocephalan ( Profilicollus sp.) varied in eiders with age, sex and year, while a cestode ( Microsomacanthus sp.) varied with host sex. Two other species of endohelminths ( Lateriporus sp., Corysonoma sp.) were not found to vary with sex, age or sampling year, and another species ( Microphallus sp.) did not vary with sex or age. Our results highlight the complexity inherent in Arctic host–parasite assemblages, and the need for more detailed studies to better understand how changing climatic conditions may affect species distributions, frequency or abundance.