title: Sex-biased gene expression and sequence conservation in Atlantic and Pacific salmon lice (Lepeophtheirus salmonis).
abstract: Salmon lice, Lepeophtheirus salmonis (Copepoda: Caligidae), are highly important ectoparasites of farmed and wild salmonids, and cause multi-million dollar losses to the salmon aquaculture industry annually. Salmon lice display extensive sexual dimorphism in ontogeny, morphology, physiology, behavior, and more. Therefore, the identification of transcripts with differential expression between males and females (sex-biased transcripts) may help elucidate the relationship between sexual selection and sexually dimorphic characteristics.
  
  
  
  Sex-biased transcripts were identified from transcriptome analyses of three L. salmonis populations, including both Atlantic and Pacific subspecies. A total of 35-43 % of all quality-filtered transcripts were sex-biased in L. salmonis, with male-biased transcripts exhibiting higher fold change than female-biased transcripts. For Gene Ontology and functional analyses, a consensus-based approach was used to identify concordantly differentially expressed sex-biased transcripts across the three populations. A total of 127 male-specific transcripts (i.e. those without detectable expression in any female) were identified, and were enriched with reproductive functions (e.g. seminal fluid and male accessory gland proteins). Other sex-biased transcripts involved in morphogenesis, feeding, energy generation, and sensory and immune system development and function were also identified. Interestingly, as observed in model systems, male-biased L. salmonis transcripts were more frequently without annotation compared to female-biased or unbiased transcripts, suggesting higher rates of sequence divergence in male-biased transcripts.
  
  
  
  Transcriptome differences between male and female L. salmonis described here provide key insights into the molecular mechanisms controlling sexual dimorphism in L. salmonis. This analysis offers targets for parasite control and provides a foundation for further analyses exploring critical topics such as the interaction between sex and drug resistance, sex-specific factors in host-parasite relationships, and reproductive roles within L. salmonis.
authors.affiliation: Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, PE, C1A 4P3, Canada.
authors.forename: Jordan D
authors.identifier: 0000-0003-1709-7163
authors.initials: JD
authors.lastname: Poley
authors.affiliation: Department of Biology, Centre for Biomedical Research, University of Victoria, 3800 Finnerty Rd, Victoria, BC, V8W 3 N5, Canada.|Present address: Département de biologie, Institut de Biologie Intégrative et des Systèms (IBIS), Université Laval, 1030 Avenue de la Medecine, Québec, QC, Canada.
authors.forename: Ben J G
authors.initials: BJ
authors.lastname: Sutherland
authors.affiliation: Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, BC, V9T 6 N7, Canada.
authors.forename: Simon R M
authors.initials: SR
authors.lastname: Jones
authors.affiliation: Department of Biology, Centre for Biomedical Research, University of Victoria, 3800 Finnerty Rd, Victoria, BC, V8W 3 N5, Canada.
authors.forename: Ben F
authors.initials: BF
authors.lastname: Koop
authors.affiliation: Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, PE, C1A 4P3, Canada. mfast@upei.ca.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Fast
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D017124:Conserved Sequence; D033342:Copepoda / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D005393:Fish Diseases / Q000469:parasitology; D015870:Gene Expression; D020869:Gene Expression Profiling; D056726:Genetic Association Studies; D005828:Genetics, Population; D006790:Host-Parasite Interactions; D008297:Male; D058977:Molecular Sequence Annotation; D010641:Phenotype; D012098:Reproduction / Q000235:genetics; D012474:Salmon / Q000469:parasitology; D012737:Sex Factors; D059467:Transcriptome
keywords: Copepoda; Evolution; Lepeophtheirus salmonis; Reproduction; Sea lice; Sex-bias; Sexual dimorphism; Transcriptomics