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1

Karyotypes of two species of the genus Pimelodus (Siluriformes, Pimelodidae)

100%
Treco F. R., Dias A. L.
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2009
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vol. 57
|
issue 1-2
43-48
EN
A cytogenetic study was conducted on two species of the genus Pimelodus that were collected from the Piquiri river, Paran?, Brazil: Pimelodus paranaensis and Pimelodus heraldoi. Both had a diploid number of 2n=56 chromosomes and a fundamental number (FN) of 104. In P. paranaensis, the karyotype consisted of 22m+22sm+4st+8a chromosomes, whereas the karyotype of P. heraldoi consisted of 18m+24sm+6st+8a. The AgNORs were localized in the terminal region of the long arm in one pair of subtelocentric chromosomes, pair 24 in P. paranaensis and pair 23 in P. heraldoi. The latter species showed size heteromorphism of these regions between the chromosome homologues. Heterochromatin was distributed mainly in the terminal regions in the two species. CMA3-positive staining was observed in some chromosomes, besides being associated with NORs, which were all DAPI-negative, in both species of Pimelodus. C-banding plus CMA3 and DAPI showed that most of the heterochromatic regions were rich in AT bases in P. paranaensis and P. heraldoi.
2

Cytogenetic characterization of Geophagus brasiliensis and two species of Gymnogeophagus (Cichlidae: Geophaginae) from Guaiba Lake, RS, Brazil

81%
Bettin_ P. L., Giuliano-Caetano L., Dias A. L.
Folia Biologica
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2010
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vol. 58
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issue 1-2
29-34
EN
The karyotypes of three species of fish of the Cichlidae family from the Forqueta river and several locations in Gua?ba lake/RS (Brazil) were analyzed. All species presented 2n=48, while Gymnogeophagus gymnogenys showed two karyotypic formulae: 4m+44st-a with FN=52 and 6m+42st-a with FN=54. Gymnogeophagus labiatus presented 4m+4sm+40st-a and FN=56 and Geophagus brasiliensis 4sm+44st-a and FN=52. Simple NORs were found in all species with the exception of a population of G. gymnogenys from Saco da Alemoa/Barra do Ribeiro. CMA3 staining revealed NOR sites, while DAPI staining was negative and heterochromatin was limited to pericentromeric regions and associated to NORs, except in G. labiatus. The data show a conserved pattern in Geophagus brasiliensis and karyotype variation in the species of Gymnogeophagus.
3

Analyses of the structure of NORs in two species of south American Sorubiminae fishes (Siluriformes) by means of several cytogenetic techniques

81%
Swarca A. C., Fenocchio A. S., Cestari M. M., Dias A. L.
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EN
Several cytogenetic techniques (AgNOR, C- G- and RE bandings, DAPI, CMA3 and FISH) were applied in order to analyze the structure and variability of NORs in the fish species Steindachneridion melanodermatum and S. scripta. Ag-NORs were observed on the short arm of the first acrocentric chromosome pair, coincidentally with a strong C-positive band on a large secondary constriction. In addition, NORs showed bright fluorescent signals when stained with CMA3 and treated for FISH with rDNA 18S. However, they showed negative coloration after G- and restriction enzyme banding and DAPI staining. The results evidence a substantial size polymorphism in these regions. The NOR bearing chromosomes in both species may be considered homologues because they maintain conserved characteristics, such as being interspersed with a GC-rich heterochromatin and possessing target sequences for AluI, BamHI and EcoRI.
4

Karyotypic characterization and NOR analysis by different banding techniques of Rhamdia quelen from the first plateau of the Iguacu River (Brazil)

81%
Fenocchio A. S., Swarca A. C., Cestari M. M., Dias A. L.
Folia Biologica
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2003
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vol. 51
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issue 3-4
219-222
EN
A population of R. quelen from the first plateau of the Iguacu River (Parana State, Brazil) was analyzed cytogenetically. A diploid set of 58 chromosomes was constituted by 32 M, 16 SM, 6 ST and 4 A (FN=116). In one individual a 2n=59 karyotype was determined due to the presence of one additional metacentric heterochromatic chromosome. NORs, detected by AgNO3 and CMA3 staining as well as fluorescence in situ hybridization with an 18S rDNA probe, are located at a terminal position on the short arms of a ST chromosome pair. C-banding marks the NORs and other weak bands distributed on telomeric regions of some chromosomes. These results give evidence that Rhamdia constitute, in terms of karyotypic macrostructure, a conserved group and support the idea that several synonymous species may be included in this genus.
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