A new Gyrodactylus strain on brown trout (Salmo trutta) in Jänisjärvi, Russian Karelia, and a literature revision of salmonid parasites of the genus Gyrodactylus in North-Western Russia and adjacent areas.

A Gyrodactylus parasite infected juveniles of brown trout (Salmo trutta L.) in a hatchery in Lake Janisjarvi, Russian Karelia. Molecular identification by ITS1-5.8S-ITS2 of ribosomal DNA indicated that the infection was caused by a non-segregating hybrid clone between unknown Gyrodactylus species and Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel & Vigneulle, 1999, described from brown trout collected in France. The mitochondrial CO1 was sequenced from the hybrid, but it is not available from pure G. teuchis from type locality. The mitochondrial DNA was an independent clade among the wageneri group parasites, differing from the nearest relative G. derjavinoides by 19%. Morphometric measurements of the Janisjarvi parasite were compared with separate (host specific) G. salaris strains from farmed rainbow trout and salmon in Lake Onega, and with available data on G. teuchis from Western Europe, Austria and Poland. All isolates were distinguishable by morphometry, and the measurements are a useful primary diagnostic tool for the salmonid parasites in Karelian great lakes and fish farms. Pure G. teuchis is not found on Russian territory, and the other parent of the hybrid has not been discovered yet in any other country. A mini review of Gyrodactylus on salmonids in the Russian Karelia is presented. [ABSTRACT FROM AUTHOR]