A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes Author Moreira, Camila Do Nascimento Author Ventura, Karen Author Percequillo, Alexandre Reis 0000-0001-9490-5457 cmoreirabio@gmail.com Author Yonenaga-Yassuda, Yatiyo text Zootaxa 2020 2020-11-06 4876 1 1 111 journal article 7983 10.11646/zootaxa.4876.1.1 4ee8b608-7c73-4980-9e86-3e3719e91c7f 1175-5326 4423612 190EC586-E14B-4AEF-A5EF-3DA401656159 Neacomys dubosti Karyotype: 2n = 64 and FN = 68. Autosomal complement: three small metacentric pairs, and 28 acrocentric pairs. Sex chromosomes: X, a medium submetacentric; Y, a small acrocentric. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. The X chromosome presented the short arm entirely heterochromatic. The Y chromosome presented the long arm entirely heterochromatic. G-banding was also performed. FISH with 18s rDNA sequences revealed signals of NOR on the short arm of six acrocentric pairs, and one of these chromosomes also had a NOR on the distal region of the long arm. FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed ( Silva et al . 2015 , pp. 4, Fig. 2C ). According to Silva et al . (2015) this karyotype was similar to N. spinosus reported by Patton et al . (2000) (2n = 64 and FN = 68), except for the morphology of the X chromosome, which was subtelocentric in N. spinosus and submetacentric in N. dubosti . Another diploid number of 62 was reported by Voss et al . (2001) for a sample from Amapá , state of Brazil ( Table 6 , Fig. 7 ).