Cerradomys langguthi (Percequillo, Hingst-Zaher & Bonvincino, 2008)

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 : 8

Cerradomys langguthi

Karyotype: 2n = 50 and FN = 56. Autosomal complement: four metacentric pairs (one large and three medium to small), and 20 acrocentric pairs (three large and 17 medium to small). Sex chromosomes: X, a medium acrocentric; Y, a small acrocentric. Variation in diploid number (2n = 46, 2n = 48 and 2n = 49) was reported due to multiple centric fusions affecting acrocentric pairs, and fundamental number and sex chromosome morphology remain the same ( Maia & Hulak 1981, pp. 35, Fig. 1 ; Geise & Pereira 2008; Percequillo et al. 2008; Geise et al. 2010). These variations in diploid number occurs sympatrically on specimens collected in Pernambuco, state of Brazil ( Table 2, Fig. 2 ). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. The X chromosome presented pericentromeric heterochromatic blocks. The Y chromosome presented a large heterochromatic block on its long arm. G-banding was also performed ( Maia & Hulak 1981).

Another karyotype for C. langguthi was reported by Nagamachi et al. (2013, pp. 8, Fig. 5 ) for a specimen from Agropalma Farm, Moju, Pará, Brazil. Karyotype: 2n = 46 and FN = 62. Autosomal complement: nine biarmed pairs (four large and five medium to small decreasing in size), and 13 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X, a large acrocentric; Y, a small acrocentric. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes, with the exception of one large metacentric pair. One medium acrocentric pair presented a heterochromatic band on proximal region of its long arm. The X chromosome presented a large heterochromatic block on the proximal region and a small band near to the distal region. The Y chromosome was almost entirely heterochromatic except for the proximal region. G-banding was also performed. FISH with telomeric sequences revealed signals at the ends of all chromosome arms, and additional telomeric sequences were found in three biarmed pairs: one pair with five interstitial telomeric sequence (one on the short arm and four on the long arm), and the others with one interstitial telomeric sequence on the centromeric regions. The authors established maps of chromosomal homology between C. langguthi and Hylaeamys megacephalus using whole chromosome probes of H. megacephalus . The results showed a huge genomic reorganization between the karyotype of these two species.

Figures

FIGURE 1. Collection localities of Oryzomyini species analyzed in this work. (1) Claúdia, Mato Grosso state; (2) and (3) Rio Japurá, Amazonas state; (4) and (5) Rio Içá, Amazonas state.

FIGURE 2. Distribution of diploid and fundamental number of karyotyped specimens of genus Cerradomys. (□) C. akroai; (■) C. goytaca; (ê) C. langguthi; (r) C. maracajuensis; (▲) C. marinhus; (○) C. scotti; (☆) C. subflavus; (l) C. vivoi.

FIGURE 5. Distribution of diploid and fundamental number of karyotyped specimens of genus Holochilus. (■) H. brasiliensis; (□) H. chacarius; (l) H. sciureus; (○) H. venezuelae; (▲) H. vulpinus.