Induction of the triploid silkworm bombyx mori by the hot water treatment to the inseminated eggs immediately after oviposition

Yokoyama, T.; Sugai, E.; Oshiki, T.; Zhong, P. Q.

When the inseminated eggs from the female of normal marking and yellow blood (J 106XCambodge; +p+y/+P Y) crossed with the male of striped and normal blood (re9;ps+y/ps+y) were treated immediately after oviposition with the hot-water of 46.degree. C for 18 min, nearly 62% of treated eggs hatched out. All larvae hatched from the treated eggs were female with yellow blood and about 92% of the larvae manifested stripe from male parent, and then they did not manifest any segregation of heterozygous blood color and showed marked sterility. These results suggested that the larvae hatched from eggs treated with hot-water were triploid. Further, the chromosome number of embryos in the treated eggs were triploid (3n = 84). And also, the number of sex-heterochromatin body per nucleus in cell of sucking stomach of the moths from the treated eggs was only one indicating a sex-chromosome structure of ZZW. From those results, it was confirmed that the reduction division in the egg nucleus is inhibited by the hot-water treatment and a resultant diploid egg nucleus (ZW) fused with the haploid sperm pronucleus (Z), then a triploid female zygote (ZZW) is formed.