Hylaeamys yunganus

Karyotype: 2n = 58 and FN = 62. Autosomal complement: three small metacentric pairs, and 25 acrocentric pairs large to small decreasing in size. Sex chromosomes: X, a large acrocentric; Y, a small acrocentric (Gardner & Patton 1976, pp. 6, Fig. 2B; Patton et al. 2000; Volobouev & Aniskin 2000). C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes and on the X chromosome. G-banding was also performed (Volobouev & Aniskin 2000).

A different karyotype was reported by Gardner & Patton (1976), with 2n = 60 and FN = 66, the karyotype of this form was nearly identical to that one mentioned before except for the presence of a small metacentric pair. Another karyotype with 2n = 60 and NF = 64 was reported by Andrades-Miranda et al. (2000). This karyotype was similar to the one reported by Gardner & Patton (1976) (2n = 60, FN = 66), the difference was due to one more acrocentric pair and one less small biarmed pair, resulting in a FN = 64. Samples from Suriname presented a diploid number from 52 to 59 and fundamental number from 64 to 67 (Koop et al. 1983; Kerridge & Baker 1990). The variation in diploid and fundamental number of samples from Suriname occurs sympatrically, whereas the others karyotypes reported for the genus represent different populations (Table 5, Fig. 6).