Spectral tuning of chemoreceptor cells in the lateral antennules of the American lobster, Homarus americanus

Chemoreceptor cells in the lateral flagellum of the first antennae (lateral antennule) of the American lobster, Homarus americanus, serve, among other functions, in long distance orientation and mediate chemical recognition of food and chemical information used in social interactions. Based upon extracellular recordings of action potentials, we report on 60 cells identified with a 15-compound equimolar mixture of mostly amino acids and a few other compounds used in previous studies of lobster chemoreceptors. Subsequently, all cells were tested with each compound separately. Forty-three percent of all cells responded strongest to hydroxyproline, 13% to taurine, and 10% to glutamate. These cells were generally narrowly tuned and had no consistent second best stimulus. Other cells were more broadly tuned and responded strongest to valine, arginine, leucine, glutamine, serine, glycine, alanine and ammonium. Most chemoreceptor cells responded less to a mixture containing their best compound than to the best compound alone, though a few gave stronger responses to the mixture. At a low concentration (10(-6) M) the mixture components enhanced the response to Hydroxyproline (Hyp); at medium and higher concentrations (10(-5) M, 10(-4) M) they suppressed the response to Hyp, resulting in a shallow, extended range of the stimulus-response function for the mixture.