Oecomys, Thomas, 1906

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 : 59

Oecomys sp. 3

Karyotype: 2n = 84 and FN = 110. Autosomal complement: 14 biarmed pairs medium to small decreasing in size, and 27 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X, a very large submetacentric (the largest chromosome of the complement); Y, a large subtelocentric ( Fig. 16 ). Due to the poor quality of chromosome preparation, was not possible to analyzed this karyotype by banding or FISH, however the C-banding pattern of sex chromosomes was presented in the inset of Fig. 16 . The X chromosome presented the long arm entirely heterochromatic. The Y chromosome was almost entirely heterochromatic. We compare the karyotype of Oecomys sp. 3 (2n = 84, FN = 110) with others Oecomys species that presents similar diploid number. The chromosome complement of O. bicolor (2n = 80, FN = 140), described by Patton et al. (2000) for samples from Rio Juruá, Acre and Amazonas states of Brazil, showed a slight similarity with Oecomys sp. 3. However, only the conventional staining was available to compare these karyotypes. Thus, a more detailed analyses of Oecomys sp. 3, using morphological and molecular approaches, was necessary to identify this specimen.

The genus Oecomys was the second most specious of tribe Oryzomyini , and the cytogenetic data reinforce such diversity. A total of 13 different diploid number, varying from 54 to 86, and 25 different fundamental numbers, varying from 54 to 142, were reported. These species exhibit autosomal and sex chromosome polymorphisms, in addition to the presence of B chromosomes. Also, there was no cytogenetic information for six species of the genus, and other six karyotypes were described as unnamed species. Based on such diversity was evident that a wide review of the genus was necessary.

Figures

FIGURE 16. Karyotype of Oecomys sp. 3, male with 2n = 84 and FN = 110, after conventional staining (JAP 143) (inset: sex chromosomes after C-banding (JAP 143)).