1994 年 60 巻 6 号 p. 673-681
Optimum conditions of hydrostatic pressure were examined for induction of two types of gynogenetic diploids (meiotic and mitotic) in the loach. Hydrostatic pressure treatment of 700 and 800kg/cm2 for 1min duration gave the best yield of normal fry when the treatment began 5min after fertilization by inhibiting the second meiosis of fertilized eggs. For mitotic gynogenesis by suppression of the first cleavage, the optimum time of application of the pressure (800kg/cm2, 1min duration) was determined to be 30 or 35min after fertilization.
In the early stage of embryos of mitotic gynogens, various aneuploids with cytogenetic aberrations were detected, in addition to induced diploids and miss-induced haploids. These were considered the major factors responsible for poor development and survival. All hatched fry of the mitotic gynogens were determined as diploid or near-diploid even in the case of severely deformed fry.
Homozygosity of the mitotic gynogens was confirmed by isozyme analysis at the protein locus MPI* which has a very high rate of gene-centromere recombination.
