Chemoreceptive Control of Feeding Processes in Hydra

Cnidarians are the simplest metazoans to exhibit satiety afterfeeding. When hydra are fed to repletion, they close their mouthsand cease to capture prey. As feeding stops, contractions ofthe tentacles and body column increase. Our earlier experimentsshowed that a gel chromatographic fraction of prey substancesinhibits prey capture. We now present evidence that the samefraction reduces the duration of mouth opening induced by reducedglutathione (GSH) and inhibits the binding of GSH to its putativereceptor. The fraction also induces column contractions whichare similar to those normally seen in sated animals. Prey substances,of unfractionated homogenate, also induce post-feeding tentaclecontractions similar to those seen in sated animals. Gut distentiondoes not appear to induce behavior associated with satiety.Therefore, these experiments suggest that chemoreception ofprey substances induce satiety in hydra. Chem. Senses 21: 313–321,1996. ³Current addresses: Monell Chemical Senses Center, 3500 MarketSt., Philadelphia, PA 19104⁴Current addresses: Department of Biology, Monmouth University,West Long Branch, NJ 07764, USA