2017 年 82 巻 4 号 p. 403-411
A discovery of nucleolar organizer regions (NORs) polymorphism and karyological analysis in the crystal eye catfish, Hemibagrus wyckii (Bleeker, 1858) from Nong Khai and Sing Buri Provinces, Thailand, were investigated. The mitotic chromosome preparation was prepared by directly from kidney cells of five male and five female specimens. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results shown that the diploid chromosome number of H. wyckii was 2n=62 and the fundamental numbers (NF) of both sexes were 110. The karyotype consists of 14 large metacentric, 14 large submetacentric, 8 large acrocentric, 8 medium metacentric, 4 medium submetacentric, 6 medium telocentric, and 8 small telocentric chromosomes. No strange size chromosomes related to sex were observed. In addition, the interstitial nucleolar organizer regions (NORs) were clearly observed at the long arm of the chromosome pair No. 12. This is the first report on polymorphism of NORs in H. wyckii. The result revealed that a heteromorphic of one male and one female had a single NOR-bearing chromosome of chromosome pair No. 12 (12a12b), while four males and four females had two NOR-bearing chromosomes of the chromosome pair No. 12 with a homomorphic (12a12a). The karyotype formula for H. wyckii is as follows:
