Karyotypic analysis of Baryancistrus

Three specimes of Baryancistrus aff. niveatus were studied cytogenetically by conventional staining, C banding, Ag-NORs, CMA3, DAPI and FISH with human telomeric probes. The results revealed a complement consisting of 52 metacentric, submetacentric and subtelocentric type chromosomes. C banding showed that heterochro-matin is located at pairs 1, 3, 6, 10, 11 and 22 in different positions. NORs were located at the short arm of pair 3, coinciding with a positive C-band. This region was also marked with CMA3, which also marked heterochromatic blocks in chromosomes 11 and 22. These regions were negatively stained by DAPI. These results revealed the presence of two different types of constitutive heterochromatin, probably due to their base composition. Chromosome bearing rDNA sites presented a difference in size in the NOR regions, probably due to heterochromatin and ribos-somal cistrons amplification. The localization of telomeric sequences by FISH revealed the conservative nature of this region. © 2004 Taylor & Francis Group, LLC

Heterochromatin patterns and karyotype relationships within and between the genera Brycon and Salminus (Pisces, Characidae)

Chromosomes of two Brycon species (B. lundii and B. microlepis) and Salminus hilarii were analyzed. Based on constitutive heterochromatin distribution patterns, karyotypic relationships within and between Bryconinae and Salmininae were examined. A monophyletic origin for the genus Brycon, comprising at least two chromosome synapomorphies (presence of two large submetacentric bearing paracentromeric and telomeric heterochromatin), is suggested. Moreover, Bryconinae and Salmininae may represent a monophyletic unit among Characidae, as they share several chromosome features.<br>Foram analisados os cromossomos de duas espécies de peixes do gênero Brycon (B. lundii e B. microlepis) e de Salminus hilarii. Principalmente baseado no padrão de distribuição da heterocromatina constitutiva, foram discutidas as relações cariotípicas dentro e entre os grupos Bryconinae e Salmininae. É sugerida uma origem monofilética para o gênero Brycon, com pelo menos duas sinapomorfias cromossômicas (presença de dois grandes submetacêntricos apresentando blocos pericentromérico e telomérico de heterocromatina constitutiva). Ainda, Bryconinae e Salmininae, compartilhando vários caracteres cromossômicos, podem formar uma unidade monofilética entre os Characidae, na qual outros caracídeos não estão incluídos

Cytotaxonomic and evolutionary considerations about karyotipic data of fishes from the Iguaçu River Basin in South of Brazil

The cytogenetic data available in the literature about the ichthyofauna of the Iguaçu River basin were analyzed in this review. The ichthyofauna was characterized by the high level of endemism and by the low diversity of species. Twenty-four of the eighty-one species were already karyotyped; six Characiformes, fourteen Siluriformes and four Perciformes. The chromosomal data showed the taxonomic and systematic complexity of the groups. Hypothesis related to the evolution of some Characiformes and Siluriformes groups from the Iguaçu River are proposed, as well as the utilization of karyotypic data for cytotaxonomy.<br>Nesta revisão são analisados os dados citogenéticos disponíveis na literatura relativos à ictiofauna da bacia do Rio Iguaçu, a qual é caracterizada pelo alto grau de endemismo e pela baixa diversidade de espécies. Das oitenta e uma espécies conhecidas, vinte e quatro já foram cariotipadas sendo 6 Characiformes, 14 Siluriformes e 4 Perciformes. Os dados cromossômicos evidenciam a complexidade taxonômica e sistemática dos grupos. São propostas hipóteses relacionadas à evolução de alguns grupos de Characiformes e Siluriformes do Rio Iguaçu, assim como o aproveitamento de dados cariotípicos para a citotaxonomia