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 : 37

Neacomys sp. 2

Karyotype: 2n = 54 and FN = 62. Autosomal complement: five medium to small metacentric and submetacentric pairs, and 21 acrocentric pairs (one large and the remaining medium to small decreasing in size). Sex chromosomes: X, a medium subtelocentric; Y, a small submetacentric ( Fig. 10A ). 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 ( Fig. 10B ). G-banding was performed to allow the correct identification of all homologous pairs ( Fig. 10C ). FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed ( Fig. 10D ). The same diploid number (2n=54) and a similar fundamental number (FN=66) was reported by Silva et al. (2017) for Neacomys sp. B. However, the former karyotype presented five large and two small biarmed pairs, different from the karyotype presented by us that comprises five medium to small biarmed pairs. The sex chromosomes morphology was also distinctly between the two karyotypes.

Figures

FIGURE 10. Karyotype of Neacomys sp. 2, male with 2n = 54 and FN = 62. (A) Conventional staining (JAP 63); (B) C-banding (JAP 63); (C) G-banding (JAP 63); (D) Metaphase plate after fluorescent in situ hybridization with telomeric probe (left) and DAPI staining (right) (JAP 63).