The Sperm from Two Male Parents Can Enter an Egg and Fuse with Both the Egg Nucleus and the Polar Body by Double Copulation in the Silkworm, Bombyx mori

摘要

In Bombyx mori, as a rule several sperm enter an egg (polyspermy), but only one sperm can fuse with the female pronucleus (Kawaguchi, 1926). Mosaics occur by unusual modes of fertilization such as polar body fertilization, androgenesis and gynogenesis. The mosaic gene (mo) was identified by Katsuki and Akiyama (1926), The females (mo/mo) produce sex-mosaic progeny (Goldschmidt and Katsuki, 1927, 1928; Ebinuma et al., 1988). Takasaki and Aratake (1959) mated two male moths each carrying different marker genes with one female moth (molmo), and got some mosaic larvae with two male marker genes. It was found that the speim of two male parents had entered one egg and they speculated that sperm from each fused with the female pronuclei. In this experiment, however, mosaic silkworms did not show the characteristics of the female parent. These mosaic silkworms might have been made by androgenesis, Strunikov (1995) obtained the bipaternal androgentic larvae originated from two male parents. Therefore, it isnot clear that sperm from two males fused with the female pronuclei. We used the egg color and the body color marker gene to determine whether each parent's sperm had entered one egg and had the ability to fuse with the egg nucleus and the polar body nucleus in the mosaic (molmo) strain of the silkworm.