Helminths of the Barents Sea Northern Fulmar (Fulmarus glacialis, Procellariiformes, Procellariidae): Composition, Impact on Host, and Indicator Properties

—The helminth fauna of the northern fulmar (Fulmarus glacialis) from the Barents Sea is described. In total 14 species of helminths (two trematodes, four cestodes, seven nematodes, and one acanthocephalan) have been found, with the cestode Tetrabothrius minor and the nematode Stegophorus stellaepolaris being the only mass parasites. The helminths fauna of fulmars in coastal areas shows significant qualitative differences: it is comprised of digeneans and an acanthocephalan absent from offshore birds. In addition, it exhibits higher species diversity of cestodes and nematodes. The intensity of invasion (II) by the cestode T. minor is the determining factor of the parasitic burden that affects the physiological state of the birds. In birds with high values of this parameter, the number of blood eosinophiles and basophiles is decreased, but on the contrary, that of neutrophiles is increased. A correlation between an increased II of birds by cestodes and growing values of the hematological index H/L (the ratio of heterophiles to lymphocytes) is revealed. This indicator can be important for in vivo diagnosis of seabird invasions by tapeworms. An analysis of the invasion of fulmars in various regions shows that their helminth fauna has almost all the necessary properties for their use as an indicator of the state of and possible changes in the pelagic ecosystems of the Barents Sea.