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 Oecomys catherinae Karyotype: 2n = 60 and FN = 62. Autosomal complement: one large subtelocentric pair, one small metacentric pair, and 27 acrocentric pairs large to small decreasing in size. Sex chromosomes: X, a large submetacentric or subtelocentric; Y, a medium acrocentric ( Andrades-Miranda et al . 2001b , pp. 272, Fig. 2A ; Andrade & Bonvicino 2003 ; Paresque et al . 2004 ; Langguth et al . 2005 ; Pinheiro & Geise 2008 ; Asfora et al . 2011 ; Malcher et al . 2017 ; SuárezVillota et al . 2017). Another fundamental number of 64 was reported due to the presence of one small metacentric pair instead of an acrocentric one ( Pinheiro & Geise 2008 ; Asfora et al . 2011 ). A different diploid number of 62 was reported due to the presence of two acrocentric pairs instead of a large subtelocentric one ( Malcher et al . 2017 ; Suárez-Villota et al . 2017 ). A diploid number of 61 was reported due to the presence of one heterochromatic acrocentric B chromosome ( Andrades-Miranda et al . 2001b ). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes and at least two small acrocentric pairs presented C-band on the distal region of the long arm. The submetacentric X chromosome presented the short arm entirely heterochromatic and a C-band on the distal region of the long arm, the subtelocentric X chromosome vary from completely heterochromatic to presenting one C-band on the long arm. The Y chromosome was entirely heterochromatic ( Andrades-Miranda et al . 2001b ; Langguth et al . 2005 ; Malcher et al . 2017 ; Suárez-Villota et al . 2017 ). G-banding was also performed ( Langguth et al . 2005 ; Malcher et al . 2017 ). Multiple NORs, varying from four to seven were localized at the telomeric regions of the short arms of acrocentric chromosomes ( Andrades-Miranda et al . 2001b ; Langguth et al . 2005 ). FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed. Maps of chromosomal homology between O. catherinae with 2n = 60 and 2n = 62, using whole chromosome probes of H. megacephalus , was established. The comparative genomic mapping between these two O. catherinae specimens shows that these karyotypes differs from each other by the occurrence of fission-fusion and translocation rearrangements ( Malcher et al . 2017 ). Another karyotype was reported by Suárez-Villota et al . (2017) . Karyotype: 2n = 54 and FN = 54. Autosomal complement: one small submetacentric pair, and 25 acrocentric pairs. Sex chromosomes: X, a large submetacentric; Y, a medium metacentric. C-banding was performed, the X chromosome presented the short arm entirely heterochrmatic and the Y chromosome was entirely heterochromatic. The variation in diploid and fundamental number of O. catherinae occurs widely distributed throughout the karyotyped specimens ( Table 8 , Fig. 13 ).