Emergence of a gynandromorph and its inferred mechanism in <i>Sasakia charonda</i> （Hewitson, 1863）

<p>In the previous study (Nagasaki et al., 2014; Yamamoto, 2017), we found that the hind wing tornal spots of Sasakia charonda display three color phenotypes, red, pink and white. We proposed that this color trait is controlled by an autosomal single locus with the following dominance order: red > pink > white. After successive breeding of this species with these genotypes, a pink heterozygote male (pi wh) was crossbred with a white homozygote female (wh wh) to confirm the inheritance of the tornal spot color in the present backcross study. The result was that pink (pi wh) and white (wh wh) offspring were born with almost the same ratio in accordance with the Mendelian inheritance. In addition, a gynandromorph having male left wings with a white tornal spot and female right wings with a pink tornal spot emerged. This gynandromorph has male external genitalia and color abnormality in the blue region of the male forewing. Since both parents of the gynandromorph have pink and white tornal spots, respectively, it is inferred that the gynandromorph occurred by abnormal oogenesis: an ovum would have two nuclei derived from the oocyte's nucleus and polar body each carrying a Z or W sex chromosome, and each nucleus would be fertilized by a separate spermatozoon carrying a Z chromosome and either a wh or a pi gene. The fertilized ovum developed into a sex mosaic adult body where the cell carrying ZZ chromosomes and wh wh genes produced a male wing with a white tornal spot, and the cell carrying ZW chromosomes and pi wh genes produced a female wing with a pink tornal spot.</p>