Acta Theriologica

, Volume 46, Issue 3, pp 269–278 | Cite as

Chromosomal description of the rodent generaOecomys andNectomys from Brazil

  • Jaqueline Andrades-Miranda
  • Luiz F. B. Oliveria
  • Nilson I. T. Zanchin
  • Margarete S. Mattevi


We analysed karyotypes of five taxa of the rodent generaOecomys andNectomys, trapped in 14 localities in an area ranging from 8° to 29°S on Brazilian territory.Oecomys cf.concolor, collected in the Amazon and in two localities of the Cerrado biome, showed a 2n=60 karyotype constituted by a pair of large subtelocentric chromosomes, a small metacentric pair and 27 acrocentric pairs. The X chromosome was a large submetacentric and a subtelo-submetacentric, the morphology of the latter showing variable C-banding patterns. In all three localities the Y chromosome was a medium size heterochromatic acrocentric. Two individuals from the Cerrado had a heterochromatic acrocentric B-chromosome.Oecomys cf.bicolor presented two cytotypes, 2n=80 in the specimens from the Cerrado biome and 2n=82 in individuals trapped in the Amazon. The 2n=80 cytotype 1 showed a large subtelocentric, 22 biarmed pairs (medium to small) and 16 acrocentric autosomal pairs. The karyotype of the 2n=82 cytotype 2 is constituted by 15 biarmed chromosomes (median to small) and 25 acrocentric pairs with heterochromatic blocks at pericentromeric regions. The sexual pairs were the same (large submetacentric X and median acrocentric Y) in both cytotypes. InO. cf.concolor and in both cytotypes ofO. cf.bicolor the nucleolar organizer regions were observed in 1-3 pairs, located in the short arms.Nectomys genus presented two cytotypes, 2n=52–55 (N. rattus, with 0–3 biarmed heterochromatic accessory chromosomes) and 2n=56–59 (N. squamipes, bearing 0–3 biarmed, heterochromatic, B-chromosomes). These 2 cytotypes occupy disjunct regions of South America, with overlapping areas in the Brazilian states of Pernambuco, Bahia, and Mato Grosso do Sul.

Key words

Oecomys concolor Oecomys bicolor Nectomys squamipes Nectomys rattus karyotype 


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Copyright information

© Mammal Research Institute, Bialowieza, Poland 2001

Authors and Affiliations

  • Jaqueline Andrades-Miranda
    • 1
  • Luiz F. B. Oliveria
    • 2
  • Nilson I. T. Zanchin
    • 1
  • Margarete S. Mattevi
    • 1
  1. 1.Departamento de GenéticaUniversidade Federal do Rio Grande do SulPorto Alegre, Rio Grande do SulBrazil
  2. 2.Museu Nacional, Setor de MastozoologiaUniversidade Federal do Rio de JaneiroRio de JaneiroBrazil

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