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Joshi J, Flores AM, Christensen KA, Johnson H, Siah A, Koop BF. An update of the salmon louse (Lepeophtheirus salmonis) reference genome assembly. G3 (BETHESDA, MD.) 2022; 12:jkac087. [PMID: 35404448 PMCID: PMC9157166 DOI: 10.1093/g3journal/jkac087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 04/04/2022] [Indexed: 11/21/2022]
Abstract
Salmon lice have plagued the salmon farming industry and have negatively impacted salmon populations in the wild. In response, researchers have generated high density genetic maps, genome assemblies, transcriptomes, and whole-genome resequencing data to better understand this parasite. In this study, we used long-read sequencing technology to update the previous genome assemblies of Atlantic Ocean salmon lice with a more contiguous assembly and a more comprehensive gene catalog of Pacific Ocean salmon lice. We were also able to further characterize genomic features previously identified from other studies by using published resequenced genomes of 25 Atlantic and 15 Pacific salmon lice. One example was further characterizing the ZW sex chromosomes. For both the Atlantic and Pacific Ocean salmon lice subspecies, we found that the female W-chromosome is only a small fraction of the Z-chromosome and that the vast majority of the W and Z-chromosome do not contain conserved regions (i.e. pseudoautosomal regions). However, conserved orthologous protein sequences can still be identified between the W- and Z-chromosomes.
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Affiliation(s)
- Jay Joshi
- Department of Biology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Anne-Marie Flores
- Department of Biology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Kris A Christensen
- Department of Biology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Hollie Johnson
- Department of Biology, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Ahmed Siah
- British Columbia Centre for Aquatic Health Sciences, Campbell River, BC V9W 2C2, Canada
| | - Ben F Koop
- Department of Biology, University of Victoria, Victoria, BC V8W 2Y2, Canada
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Wyngaard GA, Skern-Mauritzen R, Malde K, Prendergast R, Peruzzi S. The salmon louse genome may be much larger than sequencing suggests. Sci Rep 2022; 12:6616. [PMID: 35459797 PMCID: PMC9033869 DOI: 10.1038/s41598-022-10585-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 04/08/2022] [Indexed: 12/30/2022] Open
Abstract
The genome size of organisms impacts their evolution and biology and is often assumed to be characteristic of a species. Here we present the first published estimates of genome size of the ecologically and economically important ectoparasite, Lepeophtheirus salmonis (Copepoda, Caligidae). Four independent L. salmonis genome assemblies of the North Atlantic subspecies Lepeophtheirus salmonis salmonis, including two chromosome level assemblies, yield assemblies ranging from 665 to 790 Mbps. These genome assemblies are congruent in their findings, and appear very complete with Benchmarking Universal Single-Copy Orthologs analyses finding > 92% of expected genes and transcriptome datasets routinely mapping > 90% of reads. However, two cytometric techniques, flow cytometry and Feulgen image analysis densitometry, yield measurements of 1.3-1.6 Gb in the haploid genome. Interestingly, earlier cytometric measurements reported genome sizes of 939 and 567 Mbps in L. salmonis salmonis samples from Bay of Fundy and Norway, respectively. Available data thus suggest that the genome sizes of salmon lice are variable. Current understanding of eukaryotic genome dynamics suggests that the most likely explanation for such variability involves repetitive DNA, which for L. salmonis makes up ≈ 60% of the genome assemblies.
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Affiliation(s)
- Grace A Wyngaard
- Department of Biology, James Madison University, Harrisonburg, VA, USA
| | | | - Ketil Malde
- Institute of Marine Research, Bergen, Norway
- Department of Informatics, University of Bergen, Bergen, Norway
| | | | - Stefano Peruzzi
- Department of Arctic Marine Biology, UiT-the Arctic University of Norway, Tromsø, Norway.
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Guragain P, Båtnes AS, Zobolas J, Olsen Y, Bones AM, Winge P. IIb-RAD-sequencing coupled with random forest classification indicates regional population structuring and sex-specific differentiation in salmon lice ( Lepeophtheirus salmonis). Ecol Evol 2022; 12:e8809. [PMID: 35414904 PMCID: PMC8986551 DOI: 10.1002/ece3.8809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 11/29/2022] Open
Abstract
The aquaculture industry has been dealing with salmon lice problems forming serious threats to salmonid farming. Several treatment approaches have been used to control the parasite. Treatment effectiveness must be optimized, and the systematic genetic differences between subpopulations must be studied to monitor louse species and enhance targeted control measures. We have used IIb-RAD sequencing in tandem with a random forest classification algorithm to detect the regional genetic structure of the Norwegian salmon lice and identify important markers for sex differentiation of this species. We identified 19,428 single nucleotide polymorphisms (SNPs) from 95 individuals of salmon lice. These SNPs, however, were not able to distinguish the differential structure of lice populations. Using the random forest algorithm, we selected 91 SNPs important for geographical classification and 14 SNPs important for sex classification. The geographically important SNP data substantially improved the genetic understanding of the population structure and classified regional demographic clusters along the Norwegian coast. We also uncovered SNP markers that could help determine the sex of the salmon louse. A large portion of the SNPs identified to be under directional selection was also ranked highly important by random forest. According to our findings, there is a regional population structure of salmon lice associated with the geographical location along the Norwegian coastline.
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Affiliation(s)
- Prashanna Guragain
- Cell, Molecular Biology and Genomics GroupDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
- Taskforce Salmon LiceDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - Anna Solvang Båtnes
- Taskforce Salmon LiceDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - John Zobolas
- Cell, Molecular Biology and Genomics GroupDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - Yngvar Olsen
- Taskforce Salmon LiceDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - Atle M. Bones
- Cell, Molecular Biology and Genomics GroupDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
- Taskforce Salmon LiceDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - Per Winge
- Cell, Molecular Biology and Genomics GroupDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
- Taskforce Salmon LiceDepartment of BiologyNorwegian University of Science and TechnologyTrondheimNorway
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Skern-Mauritzen R, Malde K, Eichner C, Dondrup M, Furmanek T, Besnier F, Komisarczuk AZ, Nuhn M, Dalvin S, Edvardsen RB, Klages S, Huettel B, Stueber K, Grotmol S, Karlsbakk E, Kersey P, Leong JS, Glover KA, Reinhardt R, Lien S, Jonassen I, Koop BF, Nilsen F. The salmon louse genome: Copepod features and parasitic adaptations. Genomics 2021; 113:3666-3680. [PMID: 34403763 DOI: 10.1016/j.ygeno.2021.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 07/06/2021] [Accepted: 08/03/2021] [Indexed: 12/13/2022]
Abstract
Copepods encompass numerous ecological roles including parasites, detrivores and phytoplankton grazers. Nonetheless, copepod genome assemblies remain scarce. Lepeophtheirus salmonis is an economically and ecologically important ectoparasitic copepod found on salmonid fish. We present the 695.4 Mbp L. salmonis genome assembly containing ≈60% repetitive regions and 13,081 annotated protein-coding genes. The genome comprises 14 autosomes and a ZZ-ZW sex chromosome system. Assembly assessment identified 92.4% of the expected arthropod genes. Transcriptomics supported annotation and indicated a marked shift in gene expression after host attachment, including apparent downregulation of genes related to circadian rhythm coinciding with abandoning diurnal migration. The genome shows evolutionary signatures including loss of genes needed for peroxisome biogenesis, presence of numerous FNII domains, and an incomplete heme homeostasis pathway suggesting heme proteins to be obtained from the host. Despite repeated development of resistance against chemical treatments L. salmonis exhibits low numbers of many genes involved in detoxification.
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Affiliation(s)
| | - Ketil Malde
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Christiane Eichner
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Michael Dondrup
- Computational Biology Unit, Department of Informatics, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Tomasz Furmanek
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Francois Besnier
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Anna Zofia Komisarczuk
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Michael Nuhn
- EMBL-The European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, CB10 1SD, UK
| | - Sussie Dalvin
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Rolf B Edvardsen
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Sven Klages
- Sequencing Core Facility, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Bruno Huettel
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Kurt Stueber
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Sindre Grotmol
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Egil Karlsbakk
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Paul Kersey
- EMBL-The European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, CB10 1SD, UK; Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, UK
| | - Jong S Leong
- Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada
| | - Kevin A Glover
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Richard Reinhardt
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Sigbjørn Lien
- Centre for Integrative Genetics (CIGENE), Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Oluf Thesens vei 6, 1433 Ås, Norway
| | - Inge Jonassen
- Computational Biology Unit, Department of Informatics, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Ben F Koop
- Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada
| | - Frank Nilsen
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway.
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