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Abstract
Three populations of Hoplerythrinus unitaeniatus from two distinct Brazilian hydrographic basins were cytogenetically analyzed. Karyotypical variations were detected among them. The populations from Upper Paraná basin presented 2n=48, FN=96 and karyotype formula 44M/SM+4ST whereas that from São Francisco basin presented 2n=52, FN=100 and 44M/SM+4ST+4A. Constitutive heterochromatin showed a same pattern for all populations. Multiple Ag-NORs were found, ranging from four to six, and located on interstitial regions of the chromosomes, as observed in 2n=48 populations, and also in telomeric regions, as in 2n=52 specimens. Fluorescence in situ hybridizations (FISH) with 18S rDNA probe were in agreement with Ag-NORs, further revealing a size heteromorphism between NOR sites as well as additional regions than those detected by the AgNO3 staining. 5S rRNA genes were present on pericentromeric regions of M/SM chromosomes in the three populations, displaying numerical variations specific to each locality. The present study adds new data about the karyotypic diversity of H. unitaeniatus and corroborates the divergent chromosomal evolution observed within the family Erythrinidae.