Suppression of the First Cleavage and Cytogenetic Studies on the Gynogenetic Loach

Abstract

Optimum conditions of hydrostatic pressure were examined for induction of two types of gynogenetic diploids (meiotic and mitotic) in the loath. Hydrostatic pressure treatment of 700 and 800k g/cm2 for 1 min duration gave the best yield of normal fry when the treatment began 5 min 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 (800 kg/cm2, 1 min duration) was determined to be 30 or 35 min 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.

Inter-populational difference in microsatellite–centromere map distances in the loach, Misgurnus anguillicaudatus

“…In Kita population, Mado14, Mado21, Mac40 and Mac44 gave very high recombination rates (y = 0.93-1). Second meiotic division segregation frequencies larger than two-third (y = 0.67) have been noticed in gene and marker loci in previous studies in the loach (Suwa et al 1994;Morishima et al 2001Morishima et al , 2008b) and other fish species (Streisinger et al 1986;Liu et al 1992;Kauffman et al 1995;Johnson et al 1996;Nomura et al 2006;Lahrech et al 2007), suggesting the presence of strong positive chiasma interference (Thorgaard et al 1983). …”

“…Sperm was collected from loach for normal fertilization and from goldfish for gynogenesis. Goldfish sperm was UV-irradiated according to Suwa et al (1994).…”

“…In the loach, map distances of allozyme genes and microsatellite markers in relation to the centromere have been estimated in artificially induced gynogenetic diploid lines (Suwa et al 1994;Morishima et al 2001Morishima et al , 2008b, but inter-populational microsatellite-centromere (M-C) map difference was not detected between a population from the southern area of Hokkaido Island and that from Hiroshima, Honshu Island. In the present study, we produced normal diploid families and gynogenetic diploid lines in loaches collected from the genetically different populations of the northern and southern area of Hokkaido Island (Khan and Arai 2000; Arias-Rodriguez et al 2007;Morishima et al 2008a).…”

Effect of Temperature on Sex Rations of Normal and Gynogenetic Diploid Loach

“…In cross B, three groups (n=183, including 50 orange vari ants for each) were reared at different temperatures (20,25, and 30°C) from 11 to 251 days after hatching. The set up of the aquaria was the same as in Experiment 1.…”

Disruption of normal meiosis in artificial inter-populational hybrid females of Misgurnus loach

“…Sperm from Kita (K1), Memanbetsu (M1), and goldfish (GF) males were obtained by the above mentioned method. For gynogenetic induction, goldfish sperm was UV irradiated according to Suzuki et al (1985) and Suwa et al (1994).…”