Enhancement of oocyte growth in the cockroach Blaberus craniifer by a scorpion toxin, charybdotoxin.

We investigated the ovarian response of Blaberus craniifer to charybdotoxin in both imaginal molt headless females and isolated fed females, at three criteria. 1--Vitellogenesis onset, detected by immunocytochemical localisation of sites binding anti-eggs antibodies in the basal oocyte in headless females: 60% of treated females present a positive response. 2--Oocyte length at D4 during vitellogenesis of isolated fed females which was enhanced by 0.1 - 0.2 microg toxin; doses higher than 0.5 microg/female decrease ovarian growth. 3--Time of oviposition of paired females which was shortened by 24 hrs by the toxin. These results suggest that low doses charybdotoxin enhance vitellogenesis, possibly via the nervous system by means of a substance conditioning both protein synthesis by the fat body and ovarian uptake.