title: Same barcode, different biology: differential patterns of infectivity, specificity and pathogenicity in two almost identical parasite strains.
abstract: 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., grew slowly on both hosts and was non-pathogenic to Atlantic salmon. Both parasite strains reproduced successfully on Arctic charr, but the Atlantic salmon-infecting Lierelva strain grew faster on both hosts. Experiments with isolated worms revealed differences in reproductive rates which may account for the observed population differences. Atlantic salmon parasites consistently gave birth at an earlier age than the Arctic charr parasites, with the differential increasing from 1 day for the first birth up to 2-4 days for the third birth. Arctic charr-infecting parasites were more active on Atlantic salmon than salmon parasites on Arctic charr, a behavioural strategy leading to enhanced G. salaris mortality. Sequencing of 10 kb of nuclear genomic markers revealed only four single nucleotide polymorphisms, confirming that isolates of G. salaris with differences in fitness traits influencing establishment, fecundity and behaviour may be remarkably similar at a molecular level. The framework for reporting and control of G. salaris requires re-appraisal in light of the discovery of variants with such divergent biology.
authors.affiliation: Natural History Museum, Department of Research and Collections, University of Oslo, P.O. Box 1172, NO-0318 Oslo, Norway. Electronic address: raul.ramirez@nhm.uio.no.
authors.forename: Raúl
authors.initials: R
authors.lastname: Ramírez
authors.affiliation: Natural History Museum, Department of Research and Collections, University of Oslo, P.O. Box 1172, NO-0318 Oslo, Norway.
authors.forename: Tor A
authors.initials: TA
authors.lastname: Bakke
authors.affiliation: Natural History Museum, Department of Research and Collections, University of Oslo, P.O. Box 1172, NO-0318 Oslo, Norway.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Harris
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000469:parasitology; D010986:Platyhelminths / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction; D020317:Salmo salar / Q000469:parasitology*; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D014337:Trout / Q000469:parasitology*
keywords: Arctic charr; Atlantic salmon; Gyrodactylus salaris; Parasite strains; Pathogenicity; Population growth; Specificity; Transmission infectivity