Neacomys sp. 1

Karyotype: 2n = 48 and FN = 54. Autosomal complement: four small metacentric and submetacentric pairs, and 19 acrocentric pairs (one large and the remaining medium to small decreasing in size). Sex chromosomes: X, a medium subtelocentric; Y, a small acrocentric (Fig. 9A). 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 was almost entirely heterochromatic (Fig. 9B). G-banding was performed to allow the correct identification of all homologous pairs (Fig. 9C). FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed (Fig. 9D). This karyotype seems to be the same reported by Sánchez-Vendizú et al. (2018) for N. rosalindae . However, these authors appar-ently misclassified two small metacentric pairs as acrocentric. Also, the X chromosome seems to present two different morphologies, a medium submetacentric or subtelocentric. A morphological and molecular analyses of the specimens referred as Neacomys sp. 1 is necessary to test this hypothesis.