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).