A Preliminary Study on the Histomorphology of Female Embryos from a Sex-linked Balanced Lethal Silkworm Strain

In order to investigate the time and causes of death of the female embryos carrying the lethal allele l2 on the Z chromosome (hereinafter referred to as l2 embryos) in a sex-linked balanced lethal silkworm (Bombyx mori) strain,the black female eggs of a sex-linked balanced lethal silkworm strain named Ping 2 were collected at different developmental stage and histomorphological observations were conducted to l2 embryos of various developmental stages by optical microscopy after the embryos were obtained through dissection. The results showed that there was no difference between l2 embryos and normal embryos at the early embryonic developmental stage. However,when the embryos developed into the completion stage of embryonic reversal,the body surfaces of about half of them were not colored normally,suggesting that these embryos without normal color were the lethal l2 embryos. The observation on semithin sections of the female embryos showed that at the completion stage of embryonic reversal,structural integrity of tissues and organs of l2 embryos were not damaged,and no obvious difference was found in tissue structures between l2 embryos and normal embryos. These results suggest that the death of l2 embryos were due to the arrest of embryonic development rather than the abnormality of embryonic tissue structures.