Abstract
When neutral solutions of amino acids and of certain cations were applied to the cirri and mouthparts of Lepas anatifera and L. fascicularis, feeding behavior was observed. Proteins, peptides, sugars, neutral organic substances and most anions elicited no response. The order of sensitivity to amino acids did not correlate with any obvious physical or chemical property; L-glutamate, L-proline, betaine, and taurine were the most strongly stimulating substances found. It is believed that traces of amino acids and potassium ions, which are probably released when living prey is pierced by setae present on the cirri, may enable the animal to recognize and accept living and to reject non-living materials.