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.

Extensive genomic reshuffling involved in the karyotype evolution of genus Cerradomys (Rodentia: Sigmodontinae: Oryzomyini)

“…Regarding OMO Xa, this probe paints the whole X in all species, as expected since this chromosome is highly conserved among placental mammals ( Graves, 2006 ). The same probe also hybridizes to the euchromatic region of the Y that probably corresponds to the pseudoautosomal pairing region observed in other species of the tribe Oryzomyini ( Moreira et al , 2013 ; Di-Nizo et al , 2015 ).…”

Advances in cytogenetics of Brazilian rodents: cytotaxonomy, chromosome evolution and new karyotypic data

“…For example, large blocks of constitutive heterochromatin were detected in Clyomys laticeps (family Echimyidae) (Souza and Yonenaga-Yassuda 1984, Bezerra et al 2012) and a huge heterochromatic arm in Pseudoryzomys simplex (family Cricetidae, subfamily Sigmodontinae, tribe Oryzomyini) (Moreira et al 2013). C-band pattern is also an important technique for recognizing sex chromosomes, especially within the subfamily Sigmodontinae (Silva 1994, Di-Nizo 2013).…”