title: A remarkable autosomal heteromorphism in Pseudoryzomys simplex 2n = 56; FN = 54-55 (Rodentia, Sigmodontinae).
abstract: Pseudoryzomys simplex, the false rice rat, is a monotypic genus of the Oryzomyini tribe (Sigmodontinae) distributed in part of Bolivia, Paraguay, Argentina and Brazil. Its diploid number has been described as 56 acrocentric chromosomes decreasing in size and no karyotype figure has been depicted. Herein, we present karyotypic data on P. simplex, including chromosome banding and molecular fluorescent in situ hybridization using telomeric sequences and the whole X-chromosome of its sister clade Holochilus brasiliensis (HBR) as probes. A case of remarkable autosomal heteromorphism due to the presence of a whole heterochromatic arm leading to the variability of FN is reported, as well as the occurrence of regions of homology between the X and Y chromosomes (pseudoautosomal regions) after chromosome painting with the HBR X probe on P. simplex metaphases.
authors.affiliation: Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil .
authors.forename: Camila Nascimento
authors.initials: CN
authors.lastname: Moreira
authors.forename: Camilla Bruno
authors.initials: CB
authors.lastname: Di-Nizo
authors.forename: Maria José
authors.initials: MJ
authors.lastname: de Jesus Silva
authors.forename: Yatiyo
authors.initials: Y
authors.lastname: Yonenaga-Yassuda
authors.forename: Karen
authors.initials: K
authors.lastname: Ventura
keywords: Oryzomyini; cytogenetics; fluorescent in situ hybridization; heterochromatin