Neacomys, Thomas, 1900

Moreira, Camila Do Nascimento, Ventura, Karen, Percequillo, Alexandre Reis & Yonenaga-Yassuda, Yatiyo, 2020, A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes, Zootaxa 4876 (1), pp. 1-111 : 36

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.

Figures

FIGURE 9. Karyotype of Neacomys sp. 1, male with 2n = 48 and FN = 54. (A) Conventional staining (JAP 112); (B) C-banding (JAP 112); (C) G-banding (JAP 112); (D) Metaphase plate after fluorescent in situ hybridization with telomeric probe (left) and DAPI staining (right) (JAP 112).