B chromosomes in four different populations of Rhamdia quelen (Siluriformes, Heptapteridae): a comparative study of frequency and distribution
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Updated: Jun 20, 2026

Single Nucleotide Polymorphism-sensitive FISH Detection of Locus-specific Ribosomal RNA Transcription in Drosophila melanogaster
Published on: March 28, 2025
Vivian Patrícia Oliveira de Moraes1, Juliana de Souza Carneiro, Ana Lúcia Dias
1Universidade Estadual de Londrina, Centro de Ciencias Biológicas, Departamento de Biologia Geral 86051-970, Londrina, Paraná, Brasil.
Abstract:
In the present study 25 specimens of Rhamdia quelen from four different localities were analyzed cytogenetically. All showed a diploid number of 58 chromosomes, with a karyotypic formula of 36m + 16sm + 6st and FN = 116. Metacentric B chromosomes showing inter- and intraindividual variation were observed in all populations. C-banding revealed differences in the heterochromatin distribution pattern, with evidence of completely heterochromatic B chromosomes in three populations: Agua das Pedras, Agua dos Patos and Taquari rivers, and partially heterochromatic B chromosomes in the population at the fish farm station in Timbó/SC. The occurrence of B chromosomes in such distinct populations suggests that they could have arisen from the same ancestral state, before the geographic dispersal of this species.
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