Pseudoryzomys Hershkovitz 1962

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 : 77

Pseudoryzomys Hershkovitz 1962

Monotypic genus represented by P. simplex (Winge 1887) , whose distribution ranges from north-eastern Argentina, western Paraguay to eastern Bolivia, and from there eastward through Brazil and far in the north-eastern portion of this latter country ( Prado & Percequillo 2013; Voss & Myers 1991).

Karyotype: 2n = 56 and FN = 54. Autosomal complement: 27 acrocentric pairs large to small decreasing in size. Sex chromosomes: X, a large acrocentric; Y, a medium acrocentric ( Voss & Myers 1991; Oliveira & Langguth 2004; Bonvicino et al. 2005; Moreira et al. 2013, pp. 203, Fig. 2 ). An autosomal heteromorphism leading to FN = 55 was reported due to the presence of a whole heterochromatic arm in one chromosome of medium-sized with one metacentric and one acrocentric element. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. On the heteromorphic pair, the metacentric element exhibited one entirely heterochromatic arm. The X chromosome presented pericentromeric heterochromatic blocks and an interstitial lightly stained C-band on its long arm. The Y chromosome presented two conspicuous interstitial heterochromatic bands on its long arm, in addition to the pericentromeric heterochromatin. G-banding was also performed. Multiple NORs, varying from five to eight were localized at the telomeric regions of the short arms of small autosomes. FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed. FISH with whole chromosome X of Holochilus sciureus (HSC) evidenced that HSC X hybridized on the whole X chromosome of P. simplex , but also hybridized to the pericentromeric region of the Y chromosome and produced a weak interstitial signal on its long arm ( Moreira et al. 2013).

Figures

FIGURE 2. Distribution of diploid and fundamental number of karyotyped specimens of genus Cerradomys. (□) C. akroai; (■) C. goytaca; (ê) C. langguthi; (r) C. maracajuensis; (▲) C. marinhus; (○) C. scotti; (☆) C. subflavus; (l) C. vivoi.