Chromosomal Aberrations Induced by Retention of Cyprinid Fish Unfertilized Eggs in Freshwater

Chromosomes of embryos developed from eggs of bitterling retained in the freshwater or the preservative solution before fertilization were analyzed. The percentage of gastrulation had a tendency to decrease, and an increase of chromosomal aberration was observed, in proportion as the time of retention of unfertilized eggs got longer. It is presumed that the retention of eggs is one of the main causes of the karyotype differentiation. Retention of eggs is necessary to be taken notice not only in the field of fisheries in which artificial fertilization is used frequently, but also in the field concerning the conservation of species.