Karyotypic characteristics of male Oecomys auyantepui karyomorph “b”, with 2n=66: a conventional Giemsa staining (INPA 6751) b heterochromatic regions highlighted by C-banding (INPA 6751) c G-banding (INPA 6751) d nucleolus organizing region-carrying pairs revealed by silver nitrate staining (INPA 6751) e fluorescent in situ hybridization of 5S rDNA (green) and 18S rDNA (red) probes (INPA 6751) f karyotype indicating the presence of telomeric sites as well as an interstitial telomeric sequence on the X sex chromosome (INPA 6754). Bars: 10 µm.