Host specificity and seasonality of helminth component communities in central European grebes (Podicipediformes) and loons (Gaviiformes).

Structure and pattern of helminth component communities parasitizing grebes and loons are poorly understood. Here we analyze the prevalence, intensity and diversity of helminths in 505 Czech grebes (Podiceps cristatus, Podiceps nigricollis, Tachybaptus ruficollis) and loons (Gavia arctica, Gavia stellata) collected between 1962 and 2014. The species richness of helminth component communities ranged from 31±8 (P. cristatus) to 50±4 (G. stellata) species, with helminth load similar in all five host species, but with strong differences in prevalence and intensity of infection at a helminth species-specific level. The dominance was low, ranging from 0.11 (P. cristatus and G. stellata) to 0.21 (P. nigricollis). Dominant species (>25% prevalence) in P. cristatus were Confluaria sp., Tylodelphys clavata, Echinochasmus coaxatus, Petasiger neocomense and Ligula colymbi; in P. nigricollis and T. ruficollis: Confluaria sp. and Tatria sp.; in G. arctica and G. stellata: Tetrabothrius microcephalus, Stephanoprora denticulata, Cryptocotyle concava, Diplostomum gavium and Ichthyocotylurus erraticus; in G. stellata only: Echinochasmus (Monilifer) spinulosus. Four (12%) of the grebe digenean species were not locally acquired (with non-sympatric intermediate hosts) despite the fact that they represented 25% of digenean individuals found. In loons, five (28%) of digenean species and striking 38% of individuals found used the non-sympatric intermediate host species. Component communities of grebes were similar to each other (Sørensen similarity index 0.47-0.65) but differed strongly from those hosted by loons (0.00-0.20). We present the first systematically collected evidence of intra-annual changes of helminth component communities in grebes, and provide 20 new host records.