染色体操作によるサケ科魚類の三倍体及び雌性発生二倍体の生物学的特性並びに形質の遺伝に関する研究 ＶＩＩＩ 染色体操作を施したニジマス初期はいの核の行動における細胞学的観察

Abstract

Heat shock treatment for 20min from 15min after insemination suppressed the formation of the second polar body of the normally developed eggs, and the genetic material of the second polar body was retained in the egg. These processes did not result in the formation of a diploidy female pronucleus, but formed some karyomeres. They were tugged with the female pronucleus toward the male pronucleus already present in the center of the sperm aster. Thus, they adhered, and formed a fertilized nucleic group like a cluster of grapes. The genetic inactivated sperm irradiated with ultraviolet rays (UV-sperm) became swollen and formed a male pronucleus after passing through the micropile. It behaved like normal sperm until the connection with the female pronucleus. The paternal genetic material in gynogenetic embryos disappeared during the anaphase of the first cleavage, caused by the incomplete chromosome formation from the male pronucleus, and the paternal DNA remained near the cleavage plane. In the gynogenetic diploid embryo inseminated with UV-sperm, and polyploidized with heat shock treatment, the above mentioned cytological events caused by dual artificial manipulation occurred in the same egg, i.e., the genetic material formed a triploidy nucleus like a cluster of grapes, and a male pronucleus derived from UV-sperm disappeared during the anaphase of the first cleavage. The developmental rate was higher in triploid embryos polyploidized with heat shock, and lower in the gynogenetic haploid embryo than in the normal diploid embryos. In the gynogenetic diploid embryos, the metaphase of the first cleavage occurred at the same time as normal diploid embryos.