Induction of the polyploid silkworms, Bombyx mori, and their cytogenetical analysis

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Indction of polyploidy : Triploid, tetraploid and hexaploid silkworms were induced by the high-or low-temperature treatment to the inseminated eggs immediately after oviposition. The uncleus (ZW) of the diploid egg uncleus fused with the pronucleus (Z) of the haploid sperm leading to the formation of triploid female zyogote, and hexaploid silkworm was for the duplication of ZZW triploid zyogote. Disjunction of chromosomes : Triploid progenies whith hatched from one batch oviposited by tetraploid female crossed with a diploid male were indicated the abnormal segregation of sex or the blood color. These results suggested that non-disjunction of sex-chromosomes and autosomes occurred in the tetraploid oocyte of the tetraploid silkworm. Embryonic death : Some eggs oviposited by a triploid female crossed with a diploid were ferilized, none of the fertilized eggs hatched out. The embryos in these eggs were heteroploid (2.5n). Histological observation of the embryogenesis revealed of the presence of severe abnormalities and the eggs eventuelly died during subsequent embryonic development.