Digeneans of northern fur seals Callorhinus ursinus (Pinnipedia: Otariidae) from five subpopulations on St. Paul Island, Alaska

A parasitological survey of 651 northern fur seals Callorhinus ursinus L. from five subpopulations was conducted on St. Paul Island, Alaska, during July-August 2012-2014. Digenean trematodes were found in 210 of 651 fur seals with a total prevalence of 32.3%. Intensity of infection varied from 1 to 1540 parasites with mean intensity 18.4 +/- 111.1 SD and median intensity of 2 specimens per host. Significant differences in prevalence and intensity of infection in northern fur seals between separate rookeries was not observed (Mann-Whitney test; p > 0.05). Four species of digeneans belonging to the families Heterophyidae (Apophallus zalophi Price, 1932, Phocitrema fusiforme Goto and Ozaki, 1930, and Galactosomum ubelakeri (Dailey, 1969)) and Troglotrematidae (Nanophyetus salmincola (Chapin, 1926)) were found. Nanophyetus salmincola is reported from C. ursinus for the first time. We obtained partial 28S rDNA sequences for all digenean species and conducted molecular phylogenetic analysis to demonstrate their phylogenetic relationships.