DEVELOPMENTAL-CHANGES IN ECDYSTEROID BIOSYNTHESIS INVITRO DURING ADULT LIFE AND EMBRYOGENESIS IN A CRICKET, GRYLLUS-BIMACULATUS DEGEER

Ovaries from female adults of Gryllus bimaculatus produce considerable amounts of free and conjugated ecdysteroids in vitro. The rate of ecdysteroid synthesis after a 16 h incubation in Grace's medium, changes during vitellogenesis in a characteristic way, reaching a peak value of about 5 ng per hour, per animal, at days 4/5 after ecdysis, when animals start to deposit eggs. During incubation of pieces of the female abdominal integument together with the adjacent segmental fat body, a net synthesis of moulting hormones is observed, similar to that in the ovary. Ecdysteroid production by integument starts shortly after the imaginal moult and also reaches a maximum of about 3 ng per hour, per animal, around days 4/5 after ecdysis. Both tissues mainly synthesize and release ecdysone into the incubation medium. From tissues of male adult crickets only the abdominal integument shows a significant net synthesis of ecdysteroids. In vitro incubations of egg homogenates of various ages result in a net synthesis of free and conjugated ecdysteroids in older embryos, with a maximum one day before hatching of the larva. The imidazole compound KK-42 does not inhibit ecdysteroid synthesis in vitro in cricket embryos.