Reduction of Phenotypic Variation in Reproductive Traits of Clonal Strains of Ayu Plecoglossus altivelis

Abstract

Clones were induced through a mitotic-gynogenetic diploid fish in Ayu Plecoglossus altivelis, by retaining the second polar body of eggs inseminated with ultraviolet ray irradiated-sperm. The phenotypic variation in reproductive traits, such as gonad weight, spawning day, spawning duration, and the size of eggs and hatched larvae were compared betweeen normal-2N and clones. The phenotypic variations of clones were distinctly smaller than those of normal-2N. The mean values in spawning duration and the size of eggs from clones did not change over several generations. The genetic variation indices (GVI) were calculated to esimate the level of genetic vatiation of reproductive traits on the basis of comparison of phenotypic variation between clones and normal-2N. GVI of eggs and hatched larvae sizes were relatively high, suggesting the high heritability in normal-2N.