Genetic studies on the Pacific abalone. XX. Induction of gynogenetic diploid by inhibiting second meiosis in the Pacific abalone.

Successful inductions of gynogenesis and of the two kinds of triploid animals of the Pacific abalone Haliotis discus hannai have been reported. After careful re-examination of various con-ditions developed before, selected were irradiation of spermatozoa by ultraviolet ray of a total dose of 1, 200erg/mm2 for genetic inactivation of paternal genomes and cold shock of zygote at 3°C for 15min, starting 32min after fertilization for retention of second polar body. A set of such treatments resulted in low survival rates of both planktonic and settled larvae but appreciable numbers of viable gynogenetic diploid, indicating 50 to 60 percentage induction of gynogenetic di-ploid among the animals survived. Simultaneous induction of some aneuploid animals was observ-ed through the analyses of isozyme genotypes. Comparison of the shell-length distributions be-tween the sib animals demonstrated that gynogenetic diploid animals revealed enlarged variances and marked deviations in mean values towards either bigger or smaller direction in comparison with those of normal diploid animals.