Mass leech infestation of sculpin fish in Lake Baikal, with clarification of disease-prone species and parasite taxonomy.

Sculpin fish bdellosis in Lake Baikal is caused by leech ectoparasites, which are identified as belonging to the genus Baicalobdella. In addition to Cottocomephorus grewinkii, eight sculpin hosts for Baicalobdella are newly recorded: Paracottus knerii (Cottocomephorinae), and Abyssocottus korotneffi, Asprocottus platycephalus, Batrachocottus baicalensis, Batrachocottus multiradiatus, Cyphocottus megalops, Limnocottus griseus and Procottus major (Abyssocottinae). These host fishes are mass infected by Baicalobdella leeches (up to 75%) in different sites of Lake Baikal. Comparative morphological analysis of Baicalobdella infecting sculpin fishes vs. Baicalobdella torquata proper revealed nine distinctive features that allow confirming a separate systematic position and revalidating original name Baicalobdella cottidarum Dogiel, 1957.