V.P.O. Moraes, S.S. Cereali, O. Froehlich, A.L. Dias

Published September 30, 2007
Genet. Mol. Res. 6 (3): 627-633 (2007)

About the authors
V.P.O. Moraes, S.S. Cereali, O. Froehlich, A.L. Dias

Corresponding author: A.L. Dias
E-mail: anadias@uel.br

ABSTRACT

We made a cytogenetic study of the fish Rhamdia quelen collected from the Bodoquena Plateau, an isolated national park region in Mato Grosso do Sul State, Brazil. The diploid number was 2n58, with 36 metacentric + 16 submetacentric + 6 subtelo- centric chromosomes. We found one to three B chromosomes, which were metacentric and submetacentric and of medium size, showing both intra- and interindividual variation. The nucleolus organizer region (NOR) was located in the terminal region of the short arm of submetacentric pair 20. Staining with CMA, fluorochrome re- vealed the NOR location, while there was no evidence of fluorescent staining with DAPI. C banding revealed heterochromatin mainly in the terminal regions of the chromosome arms, including the NOR pair. In addition, metacentric pair 2 showed three heterochromatic blocks in the terminal portions and in the pericentromeric region. The B chromosomes appeared euchromatic. The CB + CMA, stain- ing combination demonstrated only one chromosome pair with fluo- rescence, probably the NOR-bearing one, while CB + DAPI gave various fluorescent signals, including metacentric pair 2, indicating that these heterochromatic regions are AT-rich in this population ofR. quelen. The R. quelen population in this isolated region of Brazil is chromosomally distinct from that of other populations that have been studied.

Key words: B chromosomes, C banding, Ag-NOR, Chromomycin A₁, DAPI