CHEMORECEPTIVE CONTROL OF FEEDING PROCESSES IN HYDRA

Cnidarians are the simplest metazoans to exhibit satiety after feeding . When hydra are fed to repletion, they close their mouths and cease t o capture prey. As feeding stops, contractions of the tentacles and bo dy column increase. Our earlier experiments showed that a gel chromato graphic fraction of prey substances inhibits prey capture. We now pres ent evidence that the same fraction reduces the duration of mouth open ing induced by reduced glutathione (GSH) and inhibits the binding of G SH to its putative receptor. The fraction also induces column contract ions which are similar to those normally seen in sated animals. Prey s ubstances, of unfractionated homogenate, also induce post-feeding tent acle contractions similar to those seen in sated animals. Cut distenti on does not appear to induce behavior associated with satiety. Therefo re, these experiments suggest that chemoreception of prey substances i nduce satiety in hydra.