Neacomys, Thomas, 1900

Moreira, Camila Do Nascimento, Ventura, Karen, Percequillo, Alexandre Reis & Yonenaga-Yassuda, Yatiyo, 2020, A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes, Zootaxa 4876 (1), pp. 1-111: 36

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Neacomys   sp. E

Karyotype: 2n = 62 and FN = 60. Autosomal complement: 30 acrocentric pairs (one large and the remaining medium to small decreasing in size). Sex chromosomes: X, a medium acrocentric; Y, a small acrocentric. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. The X chromosome presented a pericentromeric heterochromatic block. The Y chromosome was almost entirely heterochromatic. G-banding was also performed ( Silva et al. 2019, pp. 7, Fig. 2D View FIGURE 2 ).

Maps of chromosomal homology were established between seven karyotypes of Neacomys   species ( N. paracou   (2n = 56, FN = 64); N. spinosus   (2n = 64, FN = 68); Neacomys   sp. (cytotype 1, 2n = 58, FN = 70; and cytotype 2, 2n = 58, FN = 64); Neacomys   sp. A (2n = 58, FN = 68); Neacomys   sp. B (2n = 54, FN = 66); and Neacomys   sp. E (2n = 62, FN = 60)) by using whole chromosome probes of H. megacephalus   . The results showed that chromosome diversity between these species were due to 17 fusion/fission events, one translocation, pericentric inversions on four syntenic blocks, and six syntenic autosomal blocks with amplification/deletion of constitutive heterochromatin ( Silva et al. 2019).

We also presented two different karyotypes for the genus, mentioned here as Neacomys   sp. 1 and Neacomys   sp. 2. The cytogenetic analyzes was performed for specimens collected on the Rio Japurá and Rio Içá, Amazonas state of Brazil ( Table 1 View TABLE 1 ).