Robertsonian Fusion, Pericentric Inversion and Sex Chromosome Heteromorphisms inOryzomys Subflavus(Cricetidae, Rodentia)

Abstract
Seven different karyotypes were identified in a sample of 14 specimens of Oryzomys subflavus (2n = 56, 55 and 54; FN = 62 and 63). Homozygous and heterozygous individuals for a Robertsonian rearrangement of autosomes 5 and 6 were detected. Chromosome 5 was found to be acrocentric or subtelocentric due to a pericentric inversion. The X chromosome was acrocentric or subtelocentric, and the Y was a medium sized or a large acrocentric. The possible mechanisms of these sexual polymorphisms are considered.