Abstract
Fluorescence in situ hybridization (FISH) was undertaken in order to determinate the chromosomal distribution pattern of 18S and 5S ribosomal DNAs (rDNA) in four populations of the characid fish Astyanax altiparanae from the upper Parana river basin, Brazil. The 18S rDNA probe FISH revealed numerical and positional variations among specimens from the Kecaba stream compared to specimens of the other populations studied. In contrast to the variable 18S rDNA distribution pattern, highly stable chromosomal positioning of the 5S rDNA sites was observed in the four A. altiparanae populations. Divergence in the distribution pattern of 18S and 5S rDNA sites is also discussed.
Highlights
Piscine nucleolar organizer regions (NORs) have been extensively analyzed using silver nitrate staining (Ag-NOR) due to the simplicity of this technique
Multiple Ag-NORs have been a common characteristic in A. altiparanae, with the number reaching 10 NOR-bearing chromosomes for an A. altiparanae specimen from the Índios river in the Brazilian state of Paraná (Fernandes and Martins-Santos, 2004)
In the study described in this paper, Fluorescence in situ hybridization (FISH) was used to determine the chromosomal location of 18S and 5S ribosomal DNA (rDNA) sites in four A. altiparanae populations with the aim of contributing to the better understanding of the genomic organization of this species
Summary
Piscine nucleolar organizer regions (NORs) have been extensively analyzed using silver nitrate staining (Ag-NOR) due to the simplicity of this technique. Multiple Ag-NORs have been a common characteristic in A. altiparanae, with the number reaching 10 NOR-bearing chromosomes for an A. altiparanae specimen from the Índios river in the Brazilian state of Paraná (Fernandes and Martins-Santos, 2004).
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