Karyotype of North American shortnose sturgeon Acipenser brevirostrum with the highest chromosome number in the Acipenseriformes
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The shortnose sturgeon Acipenser brevirostrum was revealed to have a larger number of chromosomes than previously reported for other sturgeon species. Its chromosome number ranged from 362 to 372 (of ten specimens examined), showing intraindividual variation. The karyotype of metaphase with the highest chromosome number (372) consisted of 89 pairs of macrochromosomes and 97 pairs of microchromosomes (fundamental number; NF = 550). Although the microchromosomes were relatively shorter than the macrochromosomes, most of them had discernible arms and centromeres. Silver-stained nucleolar organizer regions (Ag-NORs) were localized on the telomeric regions of 5 pairs of chromosomes (Ag-NORs = 10): 4 were made up of small meta/submetacentrics and 1 of acrocentrics. Polyploidy of A. brevirostrum should be hexaploid based on the karyotype, numerous chromosomes, Ag-NORs, and previously reported large genome size (ca. 13 pg DNA/cell).
Key wordsShortnose sturgeon Acipenser brevirostrum Chromosome number Ag-NORs
Supplementary materialA color version of silver-stained metaphase of Acipenser brevirostrum (Fig. S1) is available on Springer’s server at springerlink.com
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Silver-stained metaphase of Acipenser brevirostrum with 364 chromosomes. Arrowheads indicate silver-stained nucleolar organizing regions (Ag-NORs). Bar 10 µm