EST and mitochondrial DNA sequences support a distinct Pacific form of salmon louse, Lepeophtheirus salmonis.
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.
Centre for Biomedical Research, University of Victoria, P.O. Box 3020 STN CSC, Victoria, BC, V8W 3N5, Canada.
Ryosuke
R
Yazawa
Motoshige
M
Yasuike
Jong
J
Leong
Kristian R
KR
von Schalburg
Glenn A
GA
Cooper
Marianne
M
Beetz-Sargent
Adrienne
A
Robb
William S
WS
Davidson
Simon R M
SR
Jones
Ben F
BF
Koop
D000818:Animals; D033342:Copepoda / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000235:genetics; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D015723:Gene Library; D050259:Genes, Mitochondrial; D014644:Genetic Variation; D005828:Genetics, Population; D054629:Genome, Mitochondrial; D008928:Mitochondria / Q000235:genetics; D010140:Pacific Ocean; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial; D012336:RNA, Ribosomal, 16S; D003576:Electron Transport Complex IV