Biogeographical Aspects of Helminths Parasitizing Barents Sea Birds: Spatial Distribution and Host Preferences.

To date, 53 helminth species have been discovered in the gastrointestinal tracts and other internal organs of Barents Sea birds. These parasites circulate in pelagic and coastal biocenoses. This paper analyzes their spatial distribution and host preferences in other geographical regions based on data collected by the author in the course of long-term studies and literature data. It is established that the only Barents Sea endemic is the cestode Tetrabothrius morschtini. Fifty-two species were recorded in the North Atlantic, 48 species in the North Pacific, six species in the South Atlantic, six in the Australia–New Zealand region, five in the Antarctic, four in the South Pacific, and three in the Indian Ocean basin. Analysis showed that these parasites feature two main distribution types. The amphiboreal distribution typical for the majority of species is determined by the existence of a single transarctic range of many intermediate and definitive helminth hosts in the Pliocene and the dispersion of their eggs by birds during interglacial periods of the Pleistocene. The bipolar distribution typical for 12 species is likely determined by the transfer of parasites from the Holarctic realm by their definitive hosts in the course of species divergence or during seasonal migrations. It cannot be ruled out that some helminth species have migrated from the Antarctic region to the Holarctic realm with their definitive hosts. The roles of key evolutionary–environmental factors (e.g., mobility of definitive hosts, presence of intermediate hosts, and life spans of sexually mature helminth stages) determining the biogeographical patterns of various host–parasite complexes were examined. [ABSTRACT FROM AUTHOR]