Holochilus brasiliensis

Karyotype: 2n = 40 and FN = 56. Autosomal complement: eight biarmed pairs large to small decreasing in size, one small metacentric pair, and 10 small acrocentric pairs. Sex chromosomes: X, a medium acrocentric; Y, a small acrocentric. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of eight acrocentric pairs, and two biarmed pairs. The X chromosome presented constitutive heterochromatin on the centromeric region and on the short arm, while the Y chromosome presented a distal half heterochromatic region. G-banding was also performed (Freitas et al. 1983, pp. 16, Fig. 4).