Sequence variation in four mitochondrial genes of the salmon louse Lepeophtheirus salmonis

Tjensvoll, Kjersti; Glover, Kevin A.; Nylund, Are

doi:10.3354/dao068251

Cited by 36 publications

(56 citation statements)

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“…The population genetic structure of Lepeophtheirus salmonis has been subject to several investigations throughout the Atlantic. Tentatively, previous studies can be divided into those which have revealed weak (Tjensvoll et al 2006) or no (Todd et al 2004) population genetic structure, and those revealing significant levels of genetic differentiation, sometimes over very short distances (Dixon et al 2004, Nolan & Powell 2009). To varying degrees, previous studies may be subject to technical and sampling limitations, and results may be difficult to compare between marker classes.…”

Section: Discussionmentioning

confidence: 99%

“…Some of the samples were collected on fish as they were slaughtered, while other samples were taken in association with routine lice-counting on farms. As large genetic differences between L. salmonis in the Pacific and Atlantic have previously been well documented (Todd et al 2004, Tjensvoll et al 2006, Yazawa et al 2008, no outlier sample from the Pacific was included. For Canada, Ireland, Shetland and the Faroe islands, 2 samples country -1 were collected.…”

Section: Samplesmentioning

confidence: 99%

“…However, data from the literature are divided on this issue. Analysis of 4 mitochondrial DNA (mtDNA) genes (Tjensvoll et al 2006) and 6 microsatellite DNA markers (Todd et al 2004) revealed weak or no statistically significant genetic differentiation throughout the Atlantic, respectively. Conversely, studies conducted on lice from the Pacific using the cytochrome c oxidase subunit I (COI) mtDNA gene (Boulding et al 2009), in Scotland with random amplification of polymorphic DNA (RAPD) markers (Dixon et al 2004) and in Ireland with 4 microsatellite DNA markers (Nolan & Powell 2009) have identified highly significant spatial and temporal genetic structure.…”

Section: Introductionmentioning

confidence: 99%

“…Conversely, studies conducted on lice from the Pacific using the cytochrome c oxidase subunit I (COI) mtDNA gene (Boulding et al 2009), in Scotland with random amplification of polymorphic DNA (RAPD) markers (Dixon et al 2004) and in Ireland with 4 microsatellite DNA markers (Nolan & Powell 2009) have identified highly significant spatial and temporal genetic structure. However, previous L. salmonis population genetic studies conducted in the Atlantic are characterised by small-to-modest sample sizes (Nolan et al 2000, Tjensvoll et al 2006, Nolan & Powell 2009), technical challenges (Todd et al 1997, Dixon et al 2004) and low numbers of polymorphic loci (Nolan et al 2000, Todd et al 2004, Nolan & Powell 2009.…”

Section: Introductionmentioning

confidence: 99%

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Population genetic structure of the parasitic copepod Lepeophtheirus salmonis throughout the Atlantic

Glover

Stølen²,

Messmer³

et al. 2011

Mar. Ecol. Prog. Ser.

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The parasitic copepod Lepeophtheirus salmonis is responsible for huge economic losses in the salmonid aquaculture industry, and has been linked with declines of wild salmonid populations. In order to elucidate population genetic structure throughout the Atlantic Ocean, 2495 lice representing 27 samples collected from 22 locations were analysed for 14 microsatellite loci. Significant overall genetic variation was observed (14 loci: global F ST = 0.0057, p < 0.0001), although this decreased slightly when an outlier locus (LsalSTA3), detected as a candidate for positive selection, was removed (13 neutral loci: global F ST = 0.0022, p < 0.0001). A relationship between physical and genetic distance was observed (R 2 = 0.179, p = 0.0013), but only when data from LsalSTA3 was included. No overall genetic variation was observed among the 19 samples collected in Norway (Norwegian global F ST < 0.0001, p = 0.6). None of the within-country (Canada, Ireland, Shetland and Faroe Islands) pairwise F ST values were statistically significant when analysing the 13 neutral loci and following Bonferroni correction. Samples taken at 5 Norwegian farms did not exhibit significant genetic differences before and after medicated treatment. We conclude that L. salmonis displays weak but nevertheless statistically significant population genetic variation throughout the Atlantic. Analysis of temporal samples, potentially combined with larger numbers of markers giving greater genome coverage, will be required to fully elucidate the biological significance of the observed variation.

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Section: Discussionmentioning

confidence: 99%

Section: Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Population genetic structure of the parasitic copepod Lepeophtheirus salmonis throughout the Atlantic

Glover

Stølen²,

Messmer³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…Plankton sampling discovered higher densities of L. salmonis copepodites in very shallow water along the seashore and in estuarine areas of Ireland and Scotland (Costelloe et al 1995(Costelloe et al , 1998McKibben & Hay 2004). While the same copepodite distribution may be expected in British Columbia, it requires confirmation because the Pacific and Atlantic populations of L. salmonis are genetically distinct (Tjensvoll et al 2006;Todd et al 2006) and may have different evolutionary adaptations. Thus, at least in Europe, empirical data indicated that the infective copepodites of L. salmonis concentrated in the path of migrating salmonids in estuaries.…”

Section: Research Progress (A) Larval Dispersal and Transportmentioning

confidence: 99%

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

2009

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Fishes farmed in sea pens may become infested by parasites from wild fishes and in turn become point sources for parasites. Sea lice, copepods of the family Caligidae, are the best-studied example of this risk. Sea lice are the most significant parasitic pathogen in salmon farming in Europe and the Americas, are estimated to cost the world industry E300 million a year and may also be pathogenic to wild fishes under natural conditions. Epizootics, characteristically dominated by juvenile (copepodite and chalimus) stages, have repeatedly occurred on juvenile wild salmonids in areas where farms have sea lice infestations, but have not been recorded elsewhere. This paper synthesizes the literature, including modelling studies, to provide an understanding of how one species, the salmon louse, Lepeophtheirus salmonis, can infest wild salmonids from farm sources. Three-dimensional hydrographic models predicted the distribution of the planktonic salmon lice larvae best when they accounted for wind-driven surface currents and larval behaviour. Caligus species can also cause problems on farms and transfer from farms to wild fishes, and this genus is cosmopolitan. Sea lice thus threaten finfish farming worldwide, but with the possible exception of L. salmonis, their host relationships and transmission adaptations are unknown. The increasing evidence that lice from farms can be a significant cause of mortality on nearby wild fish populations provides an additional challenge to controlling lice on the farms and also raises conservation, economic and political issues about how to balance aquaculture and fisheries resource management.

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Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

Katz,

Tetzlaff,

Johnson

et al. 2023

Trans Am Fish Soc

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ObjectiveGill lice Salmincola spp. are among the most widely reported parasites of freshwater salmonids and have been associated with recent declines in native Brook Trout Salvelinus fontinalis populations. Effective gill lice surveillance is vital for salmonid conservation success, but current survey approaches are often inadequate or problematic. We developed an environmental DNA (eDNA)‐based approach to detect the gill louse Salmincola edwardsii and explored the viability of this approach as a management tool for rapid, large‐scale gill lice surveillance at Fort McCoy, Wisconsin, USA.MethodsReference sequences were generated from gill lice specimens collected at Fort McCoy to confirm their identify as S. edwardsii and used to design a quantitative polymerase chain reaction (qPCR) assay that targets S. edwardsii mitochondrial cytochrome c oxidase I (COI). Assay validation included in silico and in vitro sensitivity and nontarget specificity testing, and assay performance was validated in situ by sampling eDNA at sites characterized via electrofishing.ResultMolecular analysis of reference sequences confirmed S. edwardsii identity while also providing the first multi‐population assessment of genetic variation for North American Salmincola and the most taxonomically comprehensive molecular phylogeny of Lernaeopodidae to date. Salmincola edwardsii eDNA was detected at 14 of 38 sites, including 12 of 14 sites with known active infestations, with no evidence that the odds of detecting gill lice via electrofishing was greater than the odds of detections from eDNA analysis. Brook Trout presence was highly predictive of gill lice eDNA site occupancy, concordant with S. edwardsii being an obligate parasite of Salvelinus fishes. However, by expanding survey coverage via eDNA analysis, we were able to identify an isolated drainage with Brook Trout where S. edwardsii is apparently absent, confirming electrofishing observations.ConclusionThese results suggest that eDNA analysis is equivalent to electrofishing for detecting gill lice in terms of performance yet offers substantial gains in survey efficiency. Further, this study demonstrates how eDNA analysis can provide valuable intel for directing management efforts, especially when used to expand survey coverage and prioritize follow‐up conventional surveys to assess host–parasite abundance, demographics, and status.

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Sequence variation in four mitochondrial genes of the salmon louse Lepeophtheirus salmonis

Cited by 36 publications

References 58 publications

Population genetic structure of the parasitic copepod Lepeophtheirus salmonis throughout the Atlantic

Population genetic structure of the parasitic copepod Lepeophtheirus salmonis throughout the Atlantic

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

Molecular identification and environmental DNA detection of gill lice ectoparasites associated with Brook Trout declines

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