A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes Author Moreira, Camila Do Nascimento Author Ventura, Karen Author Percequillo, Alexandre Reis 0000-0001-9490-5457 cmoreirabio@gmail.com Author Yonenaga-Yassuda, Yatiyo text Zootaxa 2020 2020-11-06 4876 1 1 111 journal article 7983 10.11646/zootaxa.4876.1.1 4ee8b608-7c73-4980-9e86-3e3719e91c7f 1175-5326 4423612 190EC586-E14B-4AEF-A5EF-3DA401656159 Cerradomys subflavus Karyotype: 2n = 54 and FN = 62. Autosomal complement: three large submetacentric pairs, two small metacentric pairs, and 21 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X chromosome presented two different morphologies, a large acrocentric (Xa), and a large subtelocentric (Xb); Y chromosome presented two different morphologies, a medium acrocentric (Ya), and a large acrocentric (Yb) ( Almeida & Yonenaga-Yassuda 1985 , pp. 132, Fig. 2 ; Langguth & Bonvicino 2002 ). Two different morphologies of sex chromosomes were recognized by Percequillo et al . (2008) , a medium acrocentric X and a small acrocentric Y. Variation in diploid (2n = 55 and 2n = 56) and fundamental number (FN = 63) were reported resulting from centric fusions affecting one large submetacentric pair ( Yonenaga et al . 1976 ; Almeida & Yonenaga-Yassuda 1985 ). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes, with the exception of the three submetacentric pairs, in this case only a discrete staining was observed. The Xb exhibited constitutive heterochromatin on the short arm, on the centromeric and proximal region of long arm, and an interstitial C-band was observed on its long arm. The Ya presented a large heterochromatic block on the distal portion of its long arm, amounting to about two-thirds of its length, while no heterochromatin material was detected on the pericentromeric region. G- and Q-banding were also performed ( Almeida & Yonenaga-Yassuda 1985 ). Another karyotype with 2n = 54 and FN = 64 was reported by Paresque et al . (2004) and Moreira et al . (2009) . The difference in the fundamental number was due to the presence of one small metacentric pair instead of an acrocentric one. Moreira et al . (2009) , presented another morphology for the Y chromosome, being a medium metacentric. These variations in diploid and fundamental number of C. subflavus occurs sympatrically on specimens collected in Bahia , Espírito Santo , Minas Gerais and São Paulo , states of Brazil ( Table 2 , Fig. 2 ).