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 Oligoryzomys microtis Karyotype: 2n = 64 and FN = 66. Autosomal complement: one large submetacentric pair, one small metacentric pair, and 29 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X, a medium subtelocentric; Y chromosome presented two different morphologies, a small metacentric, and a small acrocentric ( Gardner & Patton 1976 , pp. 8, Fig. 3B ; Aniskin & Volobouev 1999 ; Patton et al . 2000 ). Another fundamental number of 64 was reported for a sample from Mato Grosso , state of Brazil , due to the presence of one large acrocentric pair instead of a submetacentric one ( Di-Nizo et al . 2015 ). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of the autosomal pairs, with the exception of one the large submetacentric pair and five acrocentric pairs of medium-sized. The X chromosome presented the short arm entirely heterochromatic. The metacentric Y chromosome was entirely heterochromatic ( Aniskin & Volobouev 1999 ). G-banding was also performed ( Aniskin & Volobouev 1999 ; Di-Nizo et al . 2015 ).