The karyotypes of three species of fish of the Cichlidae family from the Forqueta river and several locations in Guaíba 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. CMA ! 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.

ABSTRACT.A large number of genera in the tropical fish family Characidae are incertae sedis. Cytogenetic analysis was made of four of these species: Astyanax eigenmanniorum, Deuterodon stigmaturus, Hyphessobrycon luetkenii, and H. anisitsi, collected from various hydrographic basins: hydrographic system from Laguna dos Patos/RS, Tramandaí basin/RS and Tibagi River basin/PR. The first two species were collected in their type locality in the State of Rio Grande do Sul. The 2n = 48 karyotype was observed only in A. eigenmanniorum, while the other species had 2n = 50 chromosomes, with different karyotypic formulas. There was weak heterochromatin staining in the pericentromeric region of A. eigenmanniorum, D. stigmaturus and H. luetkenni chromosomes. In H. anisitsi, heterochromatin appeared to be more abundant and distributed in the pericentromeric and terminal regions of the chromosomes; three pairs showed more evident heterochromatic blocks. There were multiple Ag-NORs in all populations, visualized by FISH with an 18S rDNA probe. While D. stigmaturus and H. luetkenii ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 10 (4): 3596-3608 (2011) Karyotype diversity of an incertae sedis group in Characidae 3597 had conserved AgNOR, CMA 3 and 18S rDNA sites, the other two species showed intra-and interindividual variation at these sites. The karyotype variability was high, as is common in this group of fish. Different species arising from isolated hydrographic basins maintain an elevated level of karyotype differentiation, mainly with respect to chromosome structure, heterochromatin distribution and rDNA localization. This is the first report with cytogenetic data for D. stigmaturus and H. luetkenii.

Cytogenetic analyses of the location of 18S and 5S ribosomal DNAs, and the base composition of B chromosomes of Iheringichthys labrosus from Tibagi River, Paraná, Brazil, are provided. AgNORs were observed in the terminal position on the long arm of a subtelocentric chromosome pair. CMA 3 -positive staining was observed in some chromosomes, which besides being associated with NORs, were all DAPI-negative. Chromosome B showed a strong fluorescence with CMA 3. The concomitant use of 18S and 5S rDNA probes using the FISH technique revealed 18S ribosomal cistrons in a pair of subtelocentric chromosomes, on the long arm in the terminal position, coinciding with the AgNOR. The 5S sites were found in another subtelocentric pair, on the long arm in the interstitial region, near the centromere. The findings of the present study suggest that, although there are some more conserved cytogenetic characteristics, populations of I. labrosus may show their own characteristics.Keywords: supernumerary chromosome, catfish, FISH. Análise Citogenética de DNAr 18S, 5S e cromossomo B deIheringichthys labrosus (Lütken, 1874) (Siluriformes, Pimelodidae) ResumoForam realizadas análises citogenéticas em Iheringichthys labrosus do Rio Tibagi, Paraná, Brasil com a localização cromossômica dos DNAs ribossômicos 18S e 5S e a composição de bases de seus cromossomos B. As AgNORs foram observadas em posição terminal, no braço longo de um par de cromossomos subtelocêntricos. Marcações CMA 3 positivas foram observadas em alguns cromossomos e associadas com as RONs. Porém, todas estas marcações apresentaram-se DAPI negativas. O cromossomo B mostrou-se fortemente fluorescente com CMA 3 . O uso concomitante das sondas de DNAr 18S e 5S, através da técnica de FISH, revelou os cístrons ribossômicos em um par de cromossomos subtelocêntricos, em posição terminal do braço longo, coincidindo com a AgNOR. Os sítios 5S foram observados em outro par subtelocêntrico, em posição intersticial do braço longo, próximo ao centrômero. Os resultados observados no presente estudo sugerem que, embora existam algumas características citogenéticas mais conservadas, as populações de I. labrosus podem mostrar suas próprias características.Palavras-chave: cromossomo supranumerário, catfish, FISH.

In the present cytogenetic study of Pimelodus maculatus, 13 specimens (8 males and 5 females) from the Congonhas Stream in Paraná State, Brazil, were examined using conventional staining. All of them showed a karyotype of 2n = 56, with a chromosome distribution of 20m + 20sm + 10st + 6a. However, four individuals (2 males and 2 females) were found to have a variant karyotype (cytotype) with two heteromorphic chromosomes in the group of submetacentric chromosomes -one of them corresponds to the second largest chromosome of this group and the other is a chromosome of small size. This variation suggests the existence of a structural polymorphism in the studied population.Keywords: Pimelodus, Pimelodidae, polymorphism, cytotype. Polimorfismo cromossômico estrutural em uma população de Pimelodus maculatus La Cèpede, 1803 (Siluriformes, Pimelodidae) da bacia do Rio Paranapanema, PR, Brasil ResumoNo presente estudo citogenético, foram analisados, mediante coloração convencional, 13 exemplares de Pimelodus maculatus, (8 machos e 5 fêmeas), do ribeirão Congonhas, PR, Brasil. Todos apresentaram um cariótipo com 2n = 56, distribuídos em 20 cromossomos metacêntricos (m), 20 submetacêntricos (sm), 10 subtelocêntricos (st) e 6 acrocên-tricos (a). Entretanto, 4 indivíduos (2 machos e 2 fêmeas) apresentaram um cariótipo variante (citótipo) com dois cromossomos heteromórficos no grupo dos submetacêntricos, sendo um deles o segundo maior deste grupo e o outro de tamanho pequeno. Esta variação sugere a ocorrência de um polimorfismo estrutural na população estudada.Palavras-chave: Pimelodus, Pimelodidae, polimorfismo, citótipo.

We cytogenetically analyzed 18 individuals of Cyphocharax modestus, and 41 individuals of Steindachnerina insculpta from the Tibagi River basin (Paraná State, Brazil). All the specimens had 2n = 54 chromosomes, all meta-submetacentric (M-SM). The presence of 1 or 2 B chromosomes was seen in some individuals of C. modestus of the two sampled populations, showing inter-and intra individual variation. In S. insculpta, B chromosomes were also observed but only in one population, also showing inter-and intra individual variation. C-banding was used to show that the identified B chromosomes were totally heterochromatic in the two examined species.Keywords: supernumerary chromosomes, karyotype, C-banding, fish populations. Ocorrência de cromossomos B em Cyphocharax modestus e Steindachnerina insculpta(Characiformes, Curimatidae) da bacia do Rio Tibagi (Paraná, Brasil) ResumoForam analisados, citogeneticamente, 18 indivíduos de Cyphocharax modestus e 41 indivíduos de Steindachnerina insculpta da bacia do rio Tibagi (Paraná, Brasil). Todos os espécimes apresentaram 2n = 54 cromossomos, todos do tipo meta-submetacêntrico (M-SM). A presença de 1 ou 2 cromossomos B foi detectada em alguns indivíduos de C. modestus de duas populações amostradas, evidenciando uma variação inter e intraindividual. Em S. insculpta, também foram observados cromossomos B, embora em somente uma população, mostrando também uma variação inter e intraindividual. Bandamento C foi usado para mostrar que os cromossomos B identificados apresentaram-se totalmente heterocromáticos nas duas espécies examinadas.Palavras-chave: cromossomos supranumerários, cariótipo, bandamento C, populações de peixes.