Behavioral responses of the crayfish Procambarus clarkii to single chemosensory stimuli

In some crustaceans, compounds that weakly stimulate peripheral chemoreceptor cells elicit disproportionately large behavioral responses. Here, we investigated whether this is the case in the crayfish Procambarus clarkii. Resting animals were exposed to either a blank or ammonium, glucose, glutamate, glycine, maltose, or trehalose at predicted final concentrations of 200 mu M to 2 mM. Glycine significantly increased the time spent walking. Maltose increased the time spent walking and the number of clasps of the small claws (dactyl clasps). Trehalose triggered leg probing/waving and dactyl clasping. Ammonium and glutamate failed to elicit responses. These results are consistent with the varied efficacies of those compound in stimulating leg chemoreceptor cells as determined previously with physiological methods. Glucose, however, elicited all three behaviors that we quantified - a result inconsistent with the earlier finding that glucose fails to elicit action potentials in the leg's nerve. To determine whether glucose-sensitive chemoreceptor cells are present in the legs, 150 mu l of glucose or trehalose, at concentrations of 10 mu M or 100 mu M, was applied focally to crayfish legs and dactyl-clasp frequency was determined. At a concentration of 100 mu M, glucose elicited a significantly higher dactyl-clasp frequency than at 10 mu M. Trehalose elicited high dactyl-clasp frequencies at both concentrations. Crayfish legs are, therefore, sensitive to glucose but they are more sensitive to trehalose. Overall, behavioral responses to single compounds largely paralleled the relative abilities of those compounds to stimulate leg chemoreceptor cells.