Cerradomys vivoi

Cerradomys vivoi

Karyotype: 2n = 50 and FN = 64. Autosomal complement: eight metacentric and submetacentric pairs (one large, four medium, and three small), and 16 acrocentric pairs (one large and remaining medium to small decreasing in size). Sex chromosomes: X, a medium acrocentric; Y, a slightly smaller medium acrocentric. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of small autosomes, being absent on the large autosomes and on the X chromosome, the Y chromosome had a heterochromatic block distally on the long arm. G-banding was also performed. FISH with telomeric sequences revealed signals at the ends of all chromosome arms, and additional telomeric sequences were found on the centromeric regions of one large and one medium biarmed pairs (Andrades-Miranda et al. 2002, pp. 13, Fig. 2B).

The same karyotype was reported by Pereira & Geise (2007). The authors reported a different fundamental number of 66 due to the presence of one small metacentric pair instead of an acrocentric one. Furthermore, they reported a specimen with 2n = 51, with one large acrocentric chromosome without homologous and one more pair of small acrocentric chromosomes. The basic diploid number of 2n = 50 was also reported by Percequillo et al. (2008), who also reported a different fundamental number of 62 due to a presence of one small acrocentric pair instead of a metacentric one, these authors also found a fundamental number of 63 in one male and one female, due to a pericentric inversion involving one chromosome of a medium autosome pair. Another difference was related with the size of Y chromosome smaller on these samples. These variation in diploid and fundamental number of C. vivoi occurs sympatrically on specimens collected in Bahia and Minas Gerais, states of Brazil (Table 2, Fig. 2).