The two giant sister species of the Southern Ocean, <Emphasis Type="Italic">Dissostichus eleginoides</Emphasis> and <Emphasis Type="Italic">Dissostichus mawsoni</Emphasis>, differ in karyotype and chromosomal pattern of ribosomal RNA genes |
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Authors: | L Ghigliotti F Mazzei C Ozouf-Costaz C Bonillo R Williams C-H C Cheng E Pisano |
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Institution: | (1) Department of Biology, University of Genova, Viale Benedetto XV 5, 16132 Genova, Italy;(2) Département Systématique et Evolution, CNRS UMR 7138, Museum National d’Histoire Naturelle, 43 rue Cuvier, 75005 Paris, France;(3) Antarctic Division, Channel Highway, Kingston, TAS, 7050, Australia;(4) Department of Animal Biology, University of Illinois, 515 Morrill Hall, Urbana, IL 61801, USA |
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Abstract: | The two giant notothenioid species, the Patagonian toothfish Dissostichus eleginoides and the Antarctic toothfish D. mawsoni, are important components of the Antarctic ichthyofauna and heavily exploited commercially. They have similar appearance
and size, both are piscivorous and bentho-pelagic, but differ in their geographic distribution and absence/presence of the
antifreeze trait. We karyotyped these two sister species by analyzing specimens collected from multiple Antarctic and sub-Antarctic
sites. Both species have a diploid number of 48, but differ in karyotypic formula, (2m + 2sm + 44a) for D. eleginoides and (2m + 4sm + 42a) for D. mawsoni, due to an extra pair of submetacentric chromosomes in the latter. Chromosomal fluorescence in situ hybridization with rDNA
probes revealed unexpected species-specific organization of rRNA genes; D. mawsoni possesses two rDNA loci (versus one locus in D. eleginoides), with the second locus mapping to its additional submetacentric chromosome. The additional rRNA genes in D. mawsoni may be a cold-adaptive compensatory mechanism for growth and development of this large species in freezing seawater. |
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Keywords: | Antarctica Chromosomes Dissostichus Ribosomal genes Toothfish |
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