Publications by authors named "Tor A Bakke"

The notifiable freshwater pathogen Gyrodactylus salaris Malmberg, 1957 tends to be a generalist in contrast to other monogeneans. Whilst it causes most damage to its primary host, the Atlantic salmon (Salmo salar Linnaeus), transport and reservoir hosts likely play a key role in maintaining the parasite in the environment. Here, we tested the ability of G.

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Background: Gyrodactylus salaris is a directly transmitted ectoparasite that reproduces in situ on its fish host. Wild Norwegian (East Atlantic) salmon stocks are thought to be especially susceptible to the parasite due to lack of co-adaptation, contrary to Baltic salmon stocks. This study i) identifies whether time- and density-dependent mechanisms in gyrodactylid population growth exist in G.

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Fauna Europaea provides a public web-service with an index of scientific names (including important synonyms) of all living European land and freshwater animals, their geographical distribution at country level (up to the Urals, excluding the Caucasus region), and some additional information. The Fauna Europaea project covers about 230,000 taxonomic names, including 130,000 accepted species and 14,000 accepted subspecies, which is much more than the originally projected number of 100,000 species. This represents a huge effort by more than 400 contributing specialists throughout Europe and is a unique (standard) reference suitable for many users in science, government, industry, nature conservation and education.

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Two Norwegian isolates of the monogenean Gyrodactylus salaris Malmberg, 1957 with identical cytochrome c oxidase subunit I barcodes from different hosts, show highly divergent biological and behavioural characteristics. The Lierelva parasite strain, typically infecting Atlantic salmon, Salmo salar L., grew exponentially on Atlantic salmon, but the Pålsbufjorden parasite strain, commonly infecting Arctic charr, Salvelinus alpinus L.

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Comparative studies of gyrodactylid monogeneans on different host species or strains rely upon the observation of growth on individual fish maintained within a common environment, summarised using maximum likelihood statistical approaches. Here we describe an agent-based model of gyrodactylid population growth, which we use to evaluate errors due to stochastic reproductive variation in such experimental studies. Parameters for the model use available fecundity and mortality data derived from previously published life tables of Gyrodactylus salaris, and use a new data set of fecundity and mortality statistics for this species on the Neva stock of Atlantic salmon, Salmo salar.

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Gyrodactylus teuchis is a widespread parasite of wild and farmed salmonids throughout Europe. It has been frequently confused with the notifiable pathogen G. salaris, to which it bears a striking morphological similarity.

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The monogenean flatworm Gyrodactylus thymalli (Zitnan, Helminthologia, 2:266-269, 1960) is considered a harmless ectoparasite on grayling (Thymallus thymallus). The species is closely related to G. salaris Malmberg, 1957 that causes severe gyrodactylosis on Atlantic salmon (Salmo salar) in many Norwegian rivers.

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DNA taxonomy and barcoding use nucleotide sequence data to achieve comprehensive species descriptions that facilitate reliable species diagnostics and rapid assessment of biodiversity, both of which are of great importance for parasitologists. Such molecular approaches have been applied to the monogenean genus Gyrodactylus, in particular to G. salaris, the cause of serious gyrodactylosis on Atlantic salmon.

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We present the complete mitochondrial (mt) genome of Gyrodactylus thymalli, a monogenean ectoparasite on grayling (Thymallus thymallus). The circular genome is 14788 bp in size and includes all 35 genes recognized from other flatworm mt genomes. The overall A+T content of the mt genome is 62.

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In recent years, the mitochondrial haplotype diversity of the monogenean ectoparasites Gyrodactylus salaris Malmberg, 1957 on Atlantic salmon and G. thymalli Zitnan, 1960 on grayling has been studied intensively to understand the taxonomy and phylogeography of the two species. According to these studies, neither species can be considered monophyletic, but unfortunately, the geographic sampling has mostly been restricted to Fennoscandia.

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Gyrodactylus salaris Malmberg, 1957 is a major pathogen of wild Salmo salar L. parr populations in Norway, and its delimitation from non-pathogenic species is important. The present study was undertaken to test the power of chaetotaxy to differentiate between three populations belonging to both the same and different clades (as stated by mtDNA) of G.

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Gyrodactylus thymalli Zitnan, 1960 and G. salaris Malmberg, 1957 have an indistinguishable ribosomal internal transcribed spacer (ITS) DNA sequence, but exhibit surprisingly high levels of intra- and interspecific sequence variation of the mitochondrial cytochrome oxidase I (CO1) gene. To test whether different populations of these reportedly very similar species could be discriminated using morphometric methods, we examined the morphometry of four different populations representing different mitochondrial clades.

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Approximately 800 bp of the mitochondrial cytochrome oxidase I (COI) gene were sequenced from 76 Gyrodactylus specimens of 32 salmonid host populations, i.e. from Salmo salar, Thymallus thymallus, and Oncorhynchus mykiss in Norway, Sweden and Latvia.

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The directly transmitted viviparous gyrodactylids have high species richness but low morphological and biological diversity, and many species are recorded from only a single host. They therefore constitute a guild of species ideal for studies of the evolutionary significance of host specificity. The group has the widest host range of any monogenean family, being found on 19 orders of bony fish.

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