Oligoryzomys nigripes (Olfers, 1818)

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 : 75

Oligoryzomys nigripes

Karyotype: 2n = 62 and FN = 82. Autosomal complement: one large subtelocentric pair, 10 metacentric and submetacentric pairs large to small decreasing in size, and 19 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X chromosome presented three different morphologies, a large metacentric, a large submetacentric, and a large subtelocentric; Y chromosome presented four different morphologies, a medium metacentric, a medium submetacentric, a small submetacentric, and a small subtelocentric. Different diploid numbers of 60 and 61 and fundamental number of 76 and 78 to 81 was reported due to pericentric inversions in four autosomal pairs ( Yonenaga et al. 1976; Myer & Carleton 1981, pp. 16, Fig. 5A ; Brum-Zorrilla et al. 1988; Almeida & YonenagaYassuda 1991; Espinosa & Reig 1991; Bonvicino & Weksler 1998; Andrades-Miranda et al. 2001a; Bonvicino et al. 2001; Paresque et al. 2004; Weksler & Bonvicino 2005; Paresque et al. 2007; Pereira & Geise 2007; Moreira et al. 2009; Agrellos et al. 2012; Di-Nizo et al. 2014; Di-Nizo et al. 2015; Gatto-Almeida et al. 2016). Such variation in diploid and fundamental number occurs widely distributed throughout the karyotyped specimens ( Table 9, Fig. 18 ). A diploid number of 61 was reported due to a monosomy of the X chromosome ( Andrades-Miranda et al. 2001a; Paresque et al. 2007). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. In some metaphases, three pairs of autosomes presented vestiges of telomeric heterochromatin. One arm of the metacentric X chromosome and the short arm of the submetacentric X was entirely heterochromatic. The Y chromosome was entirely heterochromatic ( Almeida & Yonenaga-Yassuda 1991; Andrades-Miranda et al. 2001a). The G- and R-banding were also performed ( Almeida & Yonenaga-Yassuda 1991; Espinosa & Reig 1991; Bonvicino et al. 2001; Di-Nizo et al. 2015). FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed ( Paresque et al. 2007).

Figures

FIGURE 5. Distribution of diploid and fundamental number of karyotyped specimens of genus Holochilus. (■) H. brasiliensis; (□) H. chacarius; (l) H. sciureus; (○) H. venezuelae; (▲) H. vulpinus.

FIGURE 18. Distribution of diploid and fundamental number of karyotyped specimens of genus Oligoryzomys. (□) O. destructor; (■) O. messorius; (○) O. nigripes; (▲) Oligoryzomys sp.; (ê) Oligoryzomys sp..