We performed a comparative analysis of the nucleolus organizer region (NOR) distribution in the karyotypes of hylid frogs from two different taxonomic groups, Hypsiboas faber and H. semilineatus. Silver nitrate staining of NORs (Ag-NORs) and fluorescence in situ hybridization (FISH) with a rDNA probe were used to investigate the chromosomal location of rDNA loci in two species. The karyotype of H. semilineatus and the Ag-NORs distribution of the four species are presented herein for the first time. After conventional staining, the four species presented very similar karyotypes with 2n = 24, but Ag-NORs analyses revealed species-specific characteristics. H. albomarginatus, H. faber and H. semilineatus had one pair of interstitial Ag-NORs in the... |