Neural and hormonal regulation of calling behavior in Blattella germanica females

Abstract

Virgin females of the German cockroach, Blattella germanica, exhibit cycles of calling behavior in relation to the cycles of corpora allata activity and ootheca production. The roles of juvenile hormone, mating, and the ootheca in the regulation of calling behavior were investigated. The onset of calling in relation to increasing rates of juvenile hormone synthesis suggested involvement of the corpora allata. Allatectomy prevented the expression of calling behavior and treatment with the juvenile hormone analog fenoxycarb restored calling. Corpus allatum denervation through nervi corporis allati transection, which accelerates the synthesis of juvenile hormone by the corpora allata, also accelerated the onset of calling. Using castrated males, timed interruption of mating and ventral nerve cord transection, we demonstrated that, while insertion of the male genitalia and/or spermatophore in the bursa copulatrix caused an immediate suppression of calling behavior, presence of sperm and/or associated seminal fluid in the spermatheca was required for the complete inhibition of calling in the first as well as in the second ovarian cycle. Although inhibitory signals from the presence of an ootheca in the genital atrium would suppress calling behavior indirectly by inhibiting corpus allatum activity, treatment of gravid females with fenoxycarb suggested that signals from the ootheca also inhibit calling directly. The ventral nerve cord plays a critical role in the transmission of inhibitory signals from mating and from the presence of the ootheca.