DAO 57:237-246 (2003)  -  doi:10.3354/dao057237

Analysis of ribosomal RNA intergenic spacer (IGS) sequences in species and populations of Gyrodactylus (Platyhelminthes: Monogenea) from salmonid fish in northern Europe

C. O. Cunningham1,*, C. M. Collins1, G. Malmberg2, T. A. Mo3

1FRS Marine Laboratory, PO Box 101, Victoria Road, Aberdeen AB11 9DB, UK
2Department of Zoology, University of Stockholm, 106 91 Stockholm, Sweden
3National Veterinary Institute, Fish Health Section, PO Box 8156 Dep., 0033 Oslo, Norway

ABSTRACT: The intergenic spacer (IGS) region of ribosomal RNA genes was amplified and sequenced from a variety of Gyrodactylus specimens collected from wild and farmed Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, and grayling Thymallus thymallus, from various locations in Northern Europe. Phylogenetic analysis of the sequences confirmed the distinction between G. salaris Malmberg, 1957 and G. thymalli Zitnan, 1960, supporting their validity as separate species. G. salaris adapted to rainbow trout are also distinct from the parasites found on Atlantic salmon, supporting the existence of a rainbow-trout form that was initially identified on the basis of morphological differences. Analysis of the IGS did not provide good resolution of different populations of G. salaris sensu stricto, but was consistent with epidemiological evidence which indicates that introduction of the parasite to Norway was recent and limited. The IGS may be helpful in distinguishing forms of G. salaris that are pathogenic to Atlantic salmon from those that are not.


KEY WORDS: Gyrodactylus salaris · Ribosomal RNA intergenic spacer · IGS · Population · Genetic variation


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