ISSN:
1573-6857
Keywords:
fish chromosomes
;
heterochromatin
;
Hypostomus
;
karyotypic diversity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Some Hypostomus species were studied concerning the features of the karyotype structure and the constitutive heterochromatin. The karyotype of sp. F from the São Francisco river (Minas Gerais state, Brazil) is now described for the first time. A diversity in the diploid number, ranging from 2n=68 to 2n=80, as well as in the karyotype formulae, is evident in this fish group. Two types of heterochromatin, GC- and AT-rich, could be identified with the use of base-specific fluorochromes. In some species heterochromatic bands are mainly located on the centromeric and telomeric chromosomal regions, while in other species they are also observed at interstitial locations. Hypotheses concerning this heterochromatic distribuition in Hypostomus karyotypes are discussed. A case of supernumerary heterochromatic segment and a centric fusion appear to be related with two variant karyotypic formulae observed among specimens from the Mogi-Guaçu and São Francisco rivers, respectively. The available data permit us to characterize a divergent karyotypic evolution among the Hypostomus species already analyzed, both at the macro- and microstructural levels, that is, their general karyotype organization and particular features related to chromosomal banding or staining, respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1003957719178
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