Abstract
Triploid hybrids between Rhodeus ocellatus ocellatus (female) and Acheilognathus limbatus (male) were artificially induced by cold shock treatment of eggs for 1h, 5min after the insemination. All of the treated eggs examined so far were triploidy. The chromosome number of the triploids was 72, and their karyotype consisted of a diploid set of the maternal species and a haploid set of the paternal species. When silver staining was applied, only NORs from the maternal species (R. o. ocellatus) were stained deeply; no NOR from the paternal species was detected. The aseptic breeding and the cell culture method with larvae newly induced in this study were very useful for facilitating breeding and chromosome studies.
