Euryoryzomys russatus

Karyotype: 2n = 80 and FN = 86. Autosomal complement: four small metacentric pairs and 35 acrocentric pairs large 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 three different morphologies, a medium submetacentric, a medium-small subtelocentric, and a small acrocentric. The differences on the X chromosome morphology, apparently was due to heterochromatin variation since the C-bands can occur on the centromeric region or the whole short arm can be heterochromatic. NORs bands were detected in two to four small acrocentric pairs. G-banding was also performed (Andrades-Miranda et al. 2000, pp. 465, Fig. 2D). This same karyotype was also reported by Silva et al. (2000), Paresque et al. (2004), Pinheiro & Geise (2008), Di-Nizo et al. (2014), and Gatto-Almeida et al. (2016). A female with 2n = 80/81 being an XX/XXX mosaic was reported by Andrades-Miranda et al. (2000).