Characteristics of Se, the white-sided egg mutation in Bombyx mori

The White-sided egg mutation (Se) of Bombyx mori produces eggs which are opaque with wrinkles in homezygotes, whereas they have gray bands on the anterior, posterior and ventral regions in heterozygotes. Here, the surface and internal chorion structures of these eggs were observed morphologically. No peculiarity was exhibited in the mutation with respect to apparent egg dimensions. When cross-sectional chorion specimens were observed using a scanning electron microscope, the internal features, mainly in the middle layer of the Se homozygous, were found to be deformed. Also the middle layer of eggs of the Se heterozygous was disordered in opaque areas. It can therefore be concluded that the Se alleles take part in the formation of the middle-layer architecture during choriogenesis.