Abstract
The present paper describes the karyotypes in the two species of abalones Nordotis discus and N. gigantea, which are found commonly in the coasts of warmer waters in Japan. Spawning was induced by ultraviolet irradiation stimulus. These larvae were obtained by artificial insemination in the laboratory. Chromosome preparations were made by the chopping method in trochophore larvae of these species. The diploid chromosome numbers were determined as 36 in these species. Thekaryotypes were composed of 10 pairs of metacentric chromosomes and 8 pairs of submetacentric chromosomes in N. discus and in N. gigantea. The fundamental number of both species was determinedas 72. Therefore, it was estimated that the chromosome complements of these species were remarkably similar. This suggests that these two species may be closely related to each other. These resultssupport successful production of the artificial hybrids between N. gigantea and N. discus in the laboratory.
