title: Seasonality of two gill monogeneans from two freshwater fish from an oligotrophic lake in northeast Finland.
abstract: The seasonal occurrence of Dactylogyrus amphibothrium and Discocotyle sagittata from the gills of ruffe (Gymnocephalus cernuus) and whitefish (Coregonus acronius), respectively was studied in Lake Yli-Kitka, a large oligotrophic lake in Northeast Finland. The lake, located near the Arctic Circle, is ice-covered for 7-8 months of the year. The prevalence of D. amphibothrium infection was 70.7% and remained high throughout all size-classes of fish. The length distribution and developmental stages of the worms indicated two generations per year. The overwintering generation produces a summer generation which lives for only a few weeks and matures in July. Discocotyle sagittata has only one generation yearly. Its worms mature and produce eggs in July-August and recruitment of the new generation starts in the autumn. The prevalence of D. sagittata infection varied between 40% (in January) and 6.7% (in September); smaller fish were more heavily infected than larger fish.
authors.affiliation: Department of Biology, University of Jyväskylä, Finland.
authors.forename: E T
authors.initials: ET
authors.lastname: Valtonen
authors.forename: M
authors.initials: M
authors.lastname: Prost
authors.forename: R
authors.initials: R
authors.lastname: Rahkonen
mesh_terms: D000818:Animals; D005387:Finland / Q000453:epidemiology; D005393:Fish Diseases / Q000453:epidemiology*; D005399:Fishes; D005618:Fresh Water; D015995:Prevalence; D012621:Seasons; D014201:Trematode Infections / Q000453:epidemiology / Q000662:veterinary*