2013 年 78 巻 4 号 p. 353-365
This is the first karyological analysis of the hoary bamboo rat (Rhizomys pruinosus) from the Nongbualamphu, Nongkhai, and Loei Provinces in northeast Thailand. Conventional staining, GTG-, CBG-, and Ag-NOR banding, and high-resolution analysis were carried out on standard whole blood T-lymphocyte cultures from six specimens of R. pruinosus from three localities. The results showed that 2n=50 and the fundamental number is 100 in both sexes. The autosomes consisted of 12 large acrocentric, 4 medium submetacentric, 6 medium acrocentric, 6 small metacentric, and 20 small acrocentric chromosomes. The X chromosome is the largest metacentric chromosome, while the Y chromosome is a small acrocentric chromosome. A multiple sex chromosome system of the X1Y,X2Y/X1X2 type was found in R. pruinosus, which is the first description in the subfamily Rhizomyinae. From GTG-banding and high-resolution techniques, the numbers of bands and locations in R. pruinosus are determined to be 234 and 280, respectively, and each chromosome pair could be clearly differentiated. CBG-banding shows C-positive (dark band) on the centromere of all autosomes. However, C-negative (light band) was observed on the Y chromosome. The results demonstrated that chromosome pair 3 had an interstitial large band on the long arm near the telomere. In addition, the short arms near the telomere of chromosome pairs 4, 7, and 10 had clear nucleolar organizer regions (NORs). This is the first report on the natural polymorphism of NORs in bamboo rats, and it indicates the presence of heteromorphism of chromosome pair 10 (10a10b) in all males and females. There are NORs in 10b, but not in 10a.