THE EXPANSION BEHAVIOR OF SEA-ANEMONES MAY BE COORDINATED BY 2 INHIBITORY NEUROPEPTIDES, ANTHO-KAAMIDE AND ANTHO-RIAMIDE

Antho-KAamide (L-3-phenyllactyl-Phe-Lys-Ala-NH2) and Antho-RIamide (L- 3-phenyllactyl-Tyr-Arg-Ile-NH2) are novel neuropeptides isolated from the sea anemone Anthopleura elegantissima. They both inhibited spontan eous contractions of isolated muscle preparations from a wide variety of anemone species (threshold around 10(-7) M). Their actions were uni versal in that they inhibited every muscle preparation tested, regardl ess of whether the muscle group was located in the ectoderm or endoder m, or was oriented in a circular or longitudinal direction. Injection of Antho-KAamide or Antho-RIamide into the coelenteron of intact sea a nemones resulted in a marked expansion of the animals. Similar shape c hanges followed feeding or exposure to soluble food extracts. Therefor e, we hypothesize that nerve cells that release Antho-KAamide and Anth o-RIamide are involved in the expansion phase of feeding behaviour in sea anemones.