Original Article

Marine Biotechnology

, Volume 10, Issue 6, pp 741-749

Open Access This content is freely available online to anyone, anywhere at any time.

EST and Mitochondrial DNA Sequences Support a Distinct Pacific Form of Salmon Louse, Lepeophtheirus salmonis

  • Ryosuke YazawaAffiliated withCentre for Biomedical Research, University of Victoria
  • , Motoshige YasuikeAffiliated withCentre for Biomedical Research, University of Victoria
  • , Jong LeongAffiliated withCentre for Biomedical Research, University of Victoria
  • , Kristian R. von SchalburgAffiliated withCentre for Biomedical Research, University of Victoria
  • , Glenn A. CooperAffiliated withCentre for Biomedical Research, University of Victoria
  • , Marianne Beetz-SargentAffiliated withCentre for Biomedical Research, University of Victoria
  • , Adrienne RobbAffiliated withCentre for Biomedical Research, University of Victoria
  • , William S. DavidsonAffiliated withDepartment of Molecular Biology and Biochemistry, Simon Fraser University
  • , Simon R. M. JonesAffiliated withPacific Biological Station, Fisheries and Oceans Canada Email author 

Abstract

Nuclear deoxyribonucleic acid sequences from approximately 15,000 salmon louse expressed sequence tags (ESTs), the complete mitochondrial genome (16,148bp) of salmon louse, and 16S ribosomal ribonucleic acid (rRNA) and cytochrome oxidase subunit I (COI) genes from 68 salmon lice collected from Japan, Alaska, and western Canada support a Pacific lineage of Lepeophtheirus salmonis that is distinct from that occurring in the Atlantic Ocean. On average, nuclear genes are 3.2% different, the complete mitochondrial genome is 7.1% different, and 16S rRNA and COI genes are 4.2% and 6.1% different, respectively. Reduced genetic diversity within the Pacific form of L. salmonis is consistent with an introduction into the Pacific from the Atlantic Ocean. The level of divergence is consistent with the hypothesis that the Pacific form of L. salmonis coevolved with Pacific salmon (Onchorhynchus spp.) and the Atlantic form coevolved with Atlantic salmonids (Salmo spp.) independently for the last 2.5–11 million years. The level of genetic divergence coincides with the opportunity for migration of fish between the Atlantic and Pacific Ocean basins via the Arctic Ocean with the opening of the Bering Strait, approximately 5 million years ago. The genetic differences may help explain apparent differences in pathogenicity and environmental sensitivity documented for the Atlantic and Pacific forms of L. salmonis.

Keywords

Salmon lice Lepeophtheirus salmonis Expressed sequence tags (ESTs) Mitochondrial genome 16S rRNA Cytochrome oxidase subunit I (COI) gene