Insect Hormonal Regulation of Wing discs in the Silkworm, Bombyx mori

Wing discs, finally growing into the adult wings, is one of the imaginal discs in insects and it is an ideal system for studying the development process of insects. To better understand the morphological transformation and hormonal regulation of wing discs during the development, the morphology of wing discs from day 3 of 5th larval instar to day 0 of pupa were observed by separated wing disc and the paraffin sections. To determine whether the growth and differentiation of wing discs were regulated by insect hormone, ecdysone 20E and juvenile hormone analogue Methoprene were injected into the silkworm at day 3 of 5th larval instar separately. The results showed that the wing discs grown slowly at larval stage but grown quickly from day 6 of 5th larval instar. What’s more, the morphology and structure of wing discs changed significantly. The hematopoietic organ degraded gradually and the veins formed finally. The development and differentiation of the wing discs were positively regulated by the certain dose of 20E and negatively regulated by Methoprene. The above results indicated that ecdysone and juvenile hormone regulated the growth and differentiation of wing discs, resulting in the metamorphosis of wing discs.