Flukes (digeneans) are common parasites of seabirds in Arctic and subarctic regions. This study examined the distribution of such parasites in 1998 and 1999 in the intertidal zones of two study areas in SW Iceland (Skerjafjördur and Grindavik) by investigating seven species of littoral snail, Littorina saxatilis, L. obtusata, L. fabalis, Onoba aculeus, Hydrobia ventrosa, Epheria vincta and Nucella lapillus , which are known to be first intermediate hosts of many species of digenean. A total of 2556 snails was collected and the intramolluscan stages of 23 seabird digenean species were identified. The local occurrence and abundance of final hosts, such as gulls, eiders and waders, largely explain prevalence differences in the study areas. Seabird digeneans with life cycles involving two intermediate hosts and one/two free-living larvae are more frequent in the Icelandic localities studied than in coastal areas of northern Europe (Barents Sea, White Sea, northern Norway). This indicates that the environmental conditions in the coastal ecosystem of SW Iceland are favourable for the transmission of complex life cycles. Also, the abundance and diversity of both potential final hosts (birds) and second intermediate hosts (littoral invertebrates and fishes) are considered to contribute to the richness of the digenean fauna of SW Iceland.
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