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International study on Artemia: 62. Genomic relationships between Artemia franciscana and A. persimilis, inferred from chromocentre numbers
Gajardo, G.; Beardmore, J.A.; Sorgeloos, P. (2001). International study on Artemia: 62. Genomic relationships between Artemia franciscana and A. persimilis, inferred from chromocentre numbers. Heredity 87(2): 172-177
In: Heredity. The Genetical Society of Great Britain: London. ISSN 0018-067X; e-ISSN 1365-2540, more
Peer reviewed article  

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Keywords
    Acids > Organic compounds > Organic acids > Nucleic acids > DNA
    Biological speciation
    Cell constituents > Chromosomes
    Chromosome number
    Classification > Taxonomy
    Disciplines > Biology > Genetics > Cytogenetics > Nucleoproteins > Chromatin > Heterochromatin
    Evolution > Speciation
    Genomes
    Hybrids
    Speciation
    Taxa > Species > Sibling species
    Artemia franciscana Kellog, 1906 [WoRMS]
    Central America [Marine Regions]; North America [Marine Regions]
    Brackish water

Authors  Top 
  • Gajardo, G.
  • Beardmore, J.A.
  • Sorgeloos, P., more

Abstract
    Chromocentres, i.e. heavily stainable heterochromatic areas with highly repetitive DNA (a 130-bp repeat in the order of 6 x 10 super(5) copies per haploid genome) observed in the resting nucleus, are a reliable taxonomic trait and a good marker for speciation in Artemia. This chromosome marker was evaluated in populations of two New World sibling species: A. franciscana, from North, Central and South America, and A. persimilis from Argentina. Artemia persimilis showed the characteristically low average chromocentre numbers (<3) of the ancestral Mediterranean species, whilst higher numbers (>5) were seen in A. franciscana. The increase in chromocentre numbers from A. persimilis to A. franciscana occurred in a rather steady, continuous geographical pattern with an overlapping zone between both species. A north-south steady latitudinal decline of chomocentres was observed towards the equator in A. franciscana populations from the northern hemisphere, whilst the trait increased from this point towards southern latitudes with a population in Chilean Patagonia (below 52 degree S) exhibiting the highest chromocentre frequency. Since chromocentres are positively correlated with repetitive DNA content, differentiation between the species through the amplification of heterochromatin or an increased DNA content in A. franciscana (although this species has a lower diploid chromosome number), might nevertheless reflect chromosomal reorganizations between the species. Chromocentres, together with other traits, reveal a probable hybrid zone between the two species in Chilean Patagonia.

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