REPRODUCTIVE-BIOLOGY OF THE GERMAN-COCKROACH, BLATTELLA-GERMANICA - JUVENILE-HORMONE AS A PLEIOTROPIC MASTER REGULATOR

Juvenile hormone UH) exerts major pleiotropic effects on cockroach dev elopment and reproduction. The production of JH by the corpora allata (CA) in the adult female German cockroach, Blattella germanica, is dep endent upon and modulated by both internal and environmental stimuli. Mating, intake of high-quality food, social interactions, and the pres ence of vitellogenic ovaries facilitate JH synthesis. Conversely, star vation, deficient diets, enforced virginity, isolation, and a pre- or post-vitellogenic ovary cause the CA to produce less JH. Sensory stimu lation of the genital vestibulum by the ootheca also inhibits the CA v ia signals that ascend the ventral nerve cord. All these stimulatory a nd inhibitory signals are integrated by the brain, and a preponderance of favorable signals results in a graded lifting of brain inhibition, permitting the synthesis and release of JH. The effects of inhibitory signals on JH biosynthesis can be lifted experimentally by severing n ervous connections between the brain and the CA. Such an operation acc elerates activation of the CA. Besides controlling gonadal maturation in females, JH concurrently regulates the production of sexual signals , including both attractant- and courtship-eliciting pheromones, and t he behavioral expression of calling (pheromone release) and sexual rec eptivity. Although IH is required for the expression of copulatory rea diness in female B. germanica, it appears that signals associated with copulation (spermatophore, sperm, accessory secretions) can inhibit t his behavioral state even when titers of IH are permissive for recepti vity. These observations suggest that IH might regulate sexual recepti vity in females indirectly through other directives. In males, JH acce lerates not only the onset of sexual readiness but also synthesis of a ccessory reproductive products. Lastly, we present a novel cockroach c ontrol strategy that is based on the intimate association between food intake and rising JH titers in B. germanica females. IH analogs cause abortion of fertile oothecae in gravid females. In turn, rising JH ti ters and vitellogenic oocytes induce feeding in females. With strategi c placement of insecticidal baits and IH analogs, gravid females, whic h normally feed little and are difficult to control, can thus be effec tively targeted for elimination. (C) 1997 Wiley-Liss, Inc.