Printed in Great Britain CHEMOSENSITIVITY OF WALKING LEGS OF THE LOBSTER HOMARUS AMERICANUS: NEUROPHYSIOLOGICAL RESPONSE SPECTRUM AND THRESHOLDS

Responses of chemoreceptors in the walking legs of the lobster Homarus americanus to 35 individual compounds and 3 mixtures (prey odours and extracts) were studied using extracellular recording techniques. Compared against a standard mussel (Mytilus edulis) extract, these receptors were most sensitive to the amino acids L-glutamate, hydroxy-L-proline, L-aspartate, L-arginine, glycine, taurine, and L-alanine, as well as such other compounds as ammonium chloride, betaine, and the tripeptide glutathione. Most of these excitants are among those compounds most prevalent in the prey of lobsters. Some proteins and odours from live prey were also effective stimuli. In general, carbohydrates, alcohols, nucleosides, and nucleotides were only slightly excitatory. The lowest thresholds for 10 compounds ranged from 3-5x10" * to 3 ' 5 X I O ~ U M; these thresholds are lower than previously reported for crustacean taste receptors