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Pacific and Atlantic Lepeophtheirus salmonis (Krøyer, 1838) are allopatric subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subspecies novo.

Skern-Mauritzen R, Torrissen O, Glover KA - BMC Genet. (2014)

Bottom Line: Likewise, studies based on nucleotide sequencing have demonstrated that sequence differences between Atlantic and Pacific L. salmonis are highly significant, albeit smaller than the divergence observed between congeneric copepod species.Lepeophtheirus salmonis COI and 16S sequences divergence between individuals from the Pacific and the Atlantic oceans was high compared to what may be expected within a copepod species and phylogenetic analysis showed that they consistently formed monophyletic clades representing their origin from the Pacific or Atlantic oceans.Reported biological and genetic differences in L. salmonis seen in conjunction with the reported genetic diversity commonly observed between and within species demonstrate that Atlantic and Pacific L. salmonis should be regarded as two subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subsp. nov.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Marine Research, P,O, Box 1870, Nordnes, 5817, Bergen, Norway. kevin.glover@imr.no.

ABSTRACT

Background: The salmon louse Lepeophtheirus salmonis is a parasitic copepod that infects salmonids in the Pacific and Atlantic oceans. Although considered as a single species, morphological and biological differences have been reported between lice from the two oceans. Likewise, studies based on nucleotide sequencing have demonstrated that sequence differences between Atlantic and Pacific L. salmonis are highly significant, albeit smaller than the divergence observed between congeneric copepod species.

Results: We demonstrated reproductive compatibility between L. salmonis from the two oceans and successfully established F2 hybrid strains using separate maternal lines from both the Pacific and Atlantic. The infection success for the F2 hybrid strains were similar to results typically observed for non hybrid lice strains in the rearing facility used. Lepeophtheirus salmonis COI and 16S sequences divergence between individuals from the Pacific and the Atlantic oceans was high compared to what may be expected within a copepod species and phylogenetic analysis showed that they consistently formed monophyletic clades representing their origin from the Pacific or Atlantic oceans.

Conclusions: Lepeophtheirus salmonis from the Pacific and Atlantic oceans are reproductively compatible at least until adults at the F2 hybrid stage, and should not be regarded as separate species based on reproductive segregation or sequence divergence levels. Reported biological and genetic differences in L. salmonis seen in conjunction with the reported genetic diversity commonly observed between and within species demonstrate that Atlantic and Pacific L. salmonis should be regarded as two subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subsp. nov.

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Related in: MedlinePlus

Molecular Phylogeny of 16S ribosomal RNA. The evolutionary history of 249 nucleotide partial 16S rRNA sequences was inferred by using the Maximum Likelihood method. The tree with the highest log likelihood (-2387) is shown. The analysis reveals two distinct clades with 100% bootstrap support corresponding to the Atlantic and Pacific samples respectively. The Pacific and Atlantic entries from the present study are highlighted in yellow and red. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The Ls 16S Pac sequence [GenBank:KF278676] was derived from the holotype speciemen (ZMUB91335). The Ls 16S ATL sequence [GenBank:KF278677] was derived from a random female from the LsAtl strain.
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Figure 3: Molecular Phylogeny of 16S ribosomal RNA. The evolutionary history of 249 nucleotide partial 16S rRNA sequences was inferred by using the Maximum Likelihood method. The tree with the highest log likelihood (-2387) is shown. The analysis reveals two distinct clades with 100% bootstrap support corresponding to the Atlantic and Pacific samples respectively. The Pacific and Atlantic entries from the present study are highlighted in yellow and red. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The Ls 16S Pac sequence [GenBank:KF278676] was derived from the holotype speciemen (ZMUB91335). The Ls 16S ATL sequence [GenBank:KF278677] was derived from a random female from the LsAtl strain.

Mentions: The phylogenetic analysis showed that the Atlantic and Pacific sequences were found in separate clusters with 100% bootstrapping support for both 16S rRNA and cytochrome oxidase subunit I (Figures 2 and 3). The phylogenetic relationship within each ocean based on 16S and COI sequences has previously been the topic of detailed studies [9,17] and will not be discussed here.


Pacific and Atlantic Lepeophtheirus salmonis (Krøyer, 1838) are allopatric subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subspecies novo.

Skern-Mauritzen R, Torrissen O, Glover KA - BMC Genet. (2014)

Molecular Phylogeny of 16S ribosomal RNA. The evolutionary history of 249 nucleotide partial 16S rRNA sequences was inferred by using the Maximum Likelihood method. The tree with the highest log likelihood (-2387) is shown. The analysis reveals two distinct clades with 100% bootstrap support corresponding to the Atlantic and Pacific samples respectively. The Pacific and Atlantic entries from the present study are highlighted in yellow and red. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The Ls 16S Pac sequence [GenBank:KF278676] was derived from the holotype speciemen (ZMUB91335). The Ls 16S ATL sequence [GenBank:KF278677] was derived from a random female from the LsAtl strain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4007600&req=5

Figure 3: Molecular Phylogeny of 16S ribosomal RNA. The evolutionary history of 249 nucleotide partial 16S rRNA sequences was inferred by using the Maximum Likelihood method. The tree with the highest log likelihood (-2387) is shown. The analysis reveals two distinct clades with 100% bootstrap support corresponding to the Atlantic and Pacific samples respectively. The Pacific and Atlantic entries from the present study are highlighted in yellow and red. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The Ls 16S Pac sequence [GenBank:KF278676] was derived from the holotype speciemen (ZMUB91335). The Ls 16S ATL sequence [GenBank:KF278677] was derived from a random female from the LsAtl strain.
Mentions: The phylogenetic analysis showed that the Atlantic and Pacific sequences were found in separate clusters with 100% bootstrapping support for both 16S rRNA and cytochrome oxidase subunit I (Figures 2 and 3). The phylogenetic relationship within each ocean based on 16S and COI sequences has previously been the topic of detailed studies [9,17] and will not be discussed here.

Bottom Line: Likewise, studies based on nucleotide sequencing have demonstrated that sequence differences between Atlantic and Pacific L. salmonis are highly significant, albeit smaller than the divergence observed between congeneric copepod species.Lepeophtheirus salmonis COI and 16S sequences divergence between individuals from the Pacific and the Atlantic oceans was high compared to what may be expected within a copepod species and phylogenetic analysis showed that they consistently formed monophyletic clades representing their origin from the Pacific or Atlantic oceans.Reported biological and genetic differences in L. salmonis seen in conjunction with the reported genetic diversity commonly observed between and within species demonstrate that Atlantic and Pacific L. salmonis should be regarded as two subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subsp. nov.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Marine Research, P,O, Box 1870, Nordnes, 5817, Bergen, Norway. kevin.glover@imr.no.

ABSTRACT

Background: The salmon louse Lepeophtheirus salmonis is a parasitic copepod that infects salmonids in the Pacific and Atlantic oceans. Although considered as a single species, morphological and biological differences have been reported between lice from the two oceans. Likewise, studies based on nucleotide sequencing have demonstrated that sequence differences between Atlantic and Pacific L. salmonis are highly significant, albeit smaller than the divergence observed between congeneric copepod species.

Results: We demonstrated reproductive compatibility between L. salmonis from the two oceans and successfully established F2 hybrid strains using separate maternal lines from both the Pacific and Atlantic. The infection success for the F2 hybrid strains were similar to results typically observed for non hybrid lice strains in the rearing facility used. Lepeophtheirus salmonis COI and 16S sequences divergence between individuals from the Pacific and the Atlantic oceans was high compared to what may be expected within a copepod species and phylogenetic analysis showed that they consistently formed monophyletic clades representing their origin from the Pacific or Atlantic oceans.

Conclusions: Lepeophtheirus salmonis from the Pacific and Atlantic oceans are reproductively compatible at least until adults at the F2 hybrid stage, and should not be regarded as separate species based on reproductive segregation or sequence divergence levels. Reported biological and genetic differences in L. salmonis seen in conjunction with the reported genetic diversity commonly observed between and within species demonstrate that Atlantic and Pacific L. salmonis should be regarded as two subspecies: Lepeophtheirus salmonis salmonis and L. salmonis oncorhynchi subsp. nov.

Show MeSH
Related in: MedlinePlus