Scanning Electron microscopic Study on the Early Development of Silkworm Eggs (Bombyx mori L.)

Morphological changes of the surface of eggs of the silkworm Bombyx mori L. were studied during early developmental stages by scanning electron microscopy. The egg surface was covered with numerous microvilli at least until 4 h after oviposition. At 6 h the microvilli were replaced by ruffle-like microprojections. This suggests that developmental changes of the surface structure may occur without direct influence of cleavage nuclei. Immediately before blastoderm cell formation, microvilli reappeared in the presumptive groove area. The ruffles seen on the apical portion of newly-formed blastoderm cells gradually became flattened, while microvilli developed on the lateral side of the cells. The mode of blastoderm cell formation is different from the typical one seen in most species of insects.