Egg shell of Bombyx mori is porous and having many spiracles on the surface, chemical compounds of low molecular weight can pass through the shell and penetrate into egg-plasm. Present experiment concerns with MNU, a known mutagenic and carcinogenic agent that react directly with DNA and protein in living organisms. Eggs of an inbred normal strain of Bombyx were immersed in aqueous solution of MNU for 15 minutes at the age of 0.5 hr to 24 hr. Eggs at 0.5 hr age undergo meiotic division and syngamy of egg and sperm-nuclei takes place around 2 hr after oviposition, followed by synchronous cleavage mitosis with cycle 60 minutes. Gastrulation takes place at egg age 24 hr. Effect on fertilization rate was negligible after MNU-treatment at 0.5 hr age. The effectiveness of the treatment was determined by killing of embryos. Hatchability was extremely low when treated at early stages, from meiosis to second cleavage division, then increased rapidly and attained normal survival level at 8. 5 hr and thereafter treatment with MNU. Formation of cellular membrane surrounding cleavage nucleus migrated to periplasm was observable in 9. 5 hr egg. MNU-treatment also caused various anomalies in hatched larvae including malformations and monstrosities. Frequency of induced larval anomalies changing with the progress of developmental stages at the treatment was in parallel with that of killing effect. Soaking of egg in MNU solution effectively induced mutation, we discovered several mutants in descending progenies of the treatment.
All Science Journal Classification (ASJC) codes
- Polymers and Plastics