Karyotype studies were undertaken in the Japanese colored-carps, the 'Ogon' (Golden carp), the 'Kohaku' (Red and white carp) and the 'Sanshoku' (Tripple color carp) by way of comparison with the chromosomes of the wild black-carp. The basic karyotype of the colored-carp consisted basically of 6 pairs of metacentrics; 17 paired and an unpaired submetacentrics; 25 paired and an unpaired subtelocentrics and one L.C., being 2n, 99 in total. But, it is usual that the diploid number of chromosomes of the colored-carp appeared as 2n, 100 containing an L.C. and a single micro-chromosome.
Sister chromatid exchanges (SCEs) in the lung cultured cells of the Indian spiny mouse were examined at several concentrations of BrdU. The spontaneous occurrence of SCEs in this animal was determined to be 11.1/cell at the dose of 0.5μg BrdU. The frequency value was slightly higher than that of the house mouse. This may be due to less C-band heterochromatin in the Indian spiny mouse than in the house mouse.
Developmental and chromosomal aspects of giant digynic triploids were studied with three 4-cell embryos, one 8-cell embryo and one blastocyst. Without exception, they displayed normal development and a complete set of triploid chromosomal complements. Their mitotic activity was normal or even high when compared with their diploid sibs. The giant blastocyst had the largest number of blastomeres and metaphasic cells among eight blastocysts of the same batch. Suggestion is made that the triploids developing from giant oocytes are more favoured for preimplantation development than the triploids caused by any other mechanism.