Ovarian Regulation of Cyclic Changes in Size and Activity of Corpus Allatum Cells in Blattella Germanica

The roles of the ovary and egg case in the regulation of the development and activity of the corpora allata were studied in Blattella germanica adult females. The corpora allata of ovariectomized females exhibit a delayed pattern of development and activity compared with intact females. Implantation of a young ovary into ovariectomized females resulted in a faster activation of the corpora allata to the same peak juvenile hormone biosynthetic rates exhibited by intact females. Injection of 20-hydroxyecdysone caused transient declines in both the activity and the size of corpus allatum cells. Insertion of a waxed egg case into the genital atrium of ovariectomized females, with or without injection of 20-hydroxyecdysone, mimicked the 21-day pregnancy in intact females and caused corpus allatum cells to become small and inactive. The size and activity of corpus allatum cells increased again when the inserted egg case was removed manually or had been carried by the ovariectomized female for more than 3 weeks. In both intact and ovariectomized females, the activity of the corpora allata, as measured by the spontaneous and farnesoic acid-stimulated rates of juvenile hormone biosynthesis, and corpus allatum development, as reflected by the size of cells, always exhibited the same patterns and responded concurrently to the various ovarian factors. These results indicate that ovarian factors, both stimulatory and inhibitory, regulate juvenile hormone production mainly by inducing changes in the cellular machinery rather than in rate-limiting enzymes. Key Word Index: Blattella germanica; corpora allata; juvenile hormone; farnesoic acid; cell size; ovariectomy; ovarian stimulation; ovarian inhibition; 20-hydroxyecdysone; egg case