Mapping of the 18S and 5S ribosomal RNA genes in Astyanax altiparanae Garutti & Britski, 2000 (Teleostei, Characidae) from the upper Paraná river basin, Brazil

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 Paraná river basin, Brazil. The 18S rDNA probe FISH revealed numerical and positional variations among specimens from the Keçaba 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.