THE CHEMICAL CONTROL OF FEEDING IN THE PORTUGUESE MAN-OF-WAR, PHYSALIA PHYSALIS L. AND ITS BEARING ON THE EVOLUTION OF THE CNIDARIA

Abstract

1. Physalia gastrozooids, both isolated and in situ, exhibit a feeding response when exposed to low concentrations of reduced glutathione (10^-5 - 10^-6M). 2. Cysteine did not elicit the response. 3. The feeding response of the gastrozooid consisted of opening of its mouth and the subsequent spreading of its lips over a large area in an attempt to envelop the prey. This response resembles a similar GSH-induced feeding response found in Hydra. 4. The sensitivity to GSH depended upon the physiological state of the Physalia. 5. The significance of this primitive chemical coordinating mechanism in relation to the evolution of the Cnidaria and of the Metazoa as a whole is considered.