Research Article

Marine Biology

, Volume 153, Issue 6, pp 1015-1022

First online:

Mitochondrial cytochrome b variation in sleeper sharks (Squaliformes: Somniosidae)

  • Brent William MurrayAffiliated withEcosystem Science and Management Program, University of Northern British Columbia Email author 
  • , John Y. WangAffiliated withFormosacetus Research and Conservation GroupNational Museum of Marine Biology & Aquarium
  • , Shih-Chu YangAffiliated withFormosacetus Research and Conservation Group
  • , John D. StevensAffiliated withCSIRO Marine & Atmospheric Research
  • , Aaron FiskAffiliated withGreat Lakes Institute for Environment Research, University of Windsor
  • , Jörundur SvavarssonAffiliated withInstitute of Biology, University of Iceland

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Sleeper sharks are a poorly studied group of deep-sea sharks. The subgenus, Somniosus, contains three morphologically similar species: S. microcephalus found in the Arctic and North Atlantic; S. pacificus in the North Pacific; and S. antarcticus in the Southern Ocean. These sharks have been reported mainly in temperate to polar waters and occasionally in subtropical locations. They have not been recorded in tropical waters. This study investigates the relationships among the accepted species of Somniosus through analysis of mitochondrial cytochrome b sequence variation. Seventy-five samples were examined from four sampling locations in the North Pacific, Southern Ocean and North Atlantic. Twenty-one haplotypes were found. A minimum spanning parsimony network separated these haplotypes into two divergent clades, an S. microcephalus and an S. pacificus/antarcticus clade, strongly supporting the distinction of S. microcephalus as a separate species from the Pacific sleeper shark species. Analysis of genetic structure within the S. pacificus/antarcticus clade (analysis of molecular variance, allele frequency comparisons, and a nested clade analysis) showed limited or no differences amongst three populations. Further examination of genetic variation at more variable mtDNA and nuclear markers is needed to examine the species status of S. pacificus and S. antarcticus.