Takeshi Seto

Bearing of Chromosome C-banding patterns on the Classification of Eurasian Toads of the Bufo bufo Complex

Distribution of NORs and C-spots in the karyotypes was compared among six forms of the Bufo bufo complex, i.e. B. j. japonicus, B. j. formosus, B. torrenticola and B. gargarizans miyakonis from Japan, and B. b. bufo and B. b. verrucosissimus from USSR. All forms invariably possessed NORs on 6q. All the 11 pairs of homologous chromosomes had constitutive heterochromatin on the centromere region in every form of toad examined. Further, each form had pericentric heterochromatin on 1p and telomeric one on 6q. Pairs 8 and 9 lacked C-bands except the centromeric spot in every form. Other chromosomes revealed unique C-spots specific to each form, and each form could be characterized from others by the banding pattern. Comparisons of the C-banding patterns of the three forms obtained with those of the published data revealed several discrepancies, but most of them were attributed to the unlike standard in recognizing spots by the different authors. Although the C-banding pattern is suggested to have some taxonomic value, systematic relationships among the six forms cannot be directly estimated by the analyses of banding patterns.

Acoustic and karyotypic evidence for specific separation of Polypedates megacephalus from P. leucomystax

The Taiwanese population of Polypedates leucomystax megacephalus is distinct from the Bornean population of P. L leucomystax in adult morphology, mating call, and karyotype. Clear differences in the latter two characteristics suggest the presence of a high degree of genetic differ- entiation between the two populations. The Taiwanese population is therefore regarded as a full species, P. megacephalus Hallowell, 1860. Populations from continental China require further taxo- nomic investigation.

On the effects of X-irradiation on the chromosomes of Yoshida sarcoma cells. (A preliminary report)

The Yoshida sarcoma, a rat ascites tumor, was irradiated with x rays at dosages of 500, 1000, and 1500 r, and the chromosomes were observed in tumor cells. It was found that the chromosome-number mode of tumor cells in unirradiated tumor-bearing animals oecurred at 40. The chromosomes were morphologically analyzed according to the system of Tjio and Levan, and the number of chromosomes assorted in three morphological groups was 13 for M, 13 for S, and 14 for T. Breaks and translocations of chromosomes were rather common and remarkable in metaphase cells observed in irradiated tumor-animals. It was observed in individual cells that there was no constancy in the number of M, S, and T chromosomes which were unaltered by irradiation. From this result, it seems probable that there is no differential radiosensitivity by chromosomes of different types. Two chromosomes of M type are outstanding as marker elements because of their remarkably large size. In the two marker chromosomes, the frequency distribution of breakage was observed after irradiation, and showed that the breakage was rather frequent on both arms around positions one-fourth distant from the centromere.