Hormonal control of egg-laying in the marine pulmonate,Onchidium verruculatum

Extirpation of the pleurovisceral ganglia (PV) blocked egg-laying whereas reimplantation of PV or injection of a PV homogenate into PV-less animals restored the egg-laying capacity of the marine pulomonate, O. verruculatum. Injection of PV homogenate induced egg-laying in intact, mature individuals within 15–45 minutes. Boiling of the homogenate for 15 minutes did not abolish its egg-laying efficacy. However, after incubation with trypsin, a PV homogenate lost its potency. Homogenates of PV from colchicinized animals could not induce egg-laying in intact Onchidium. Similarly, colchicinized animals did not respond to a PV ectract from intact Onchidium. It is hypothesized that egg-laying in O. verruculatum is under the control of a heat-stable, trypsin sensitive hormone secreted by the PV ganglia.