Mixture suppression in behavior: the antennular flick response in the spiny lobster towards binary odorant mixtures

The behavioral responses of Florida spiny lobsters towards various concentrations of binary mixtures and their constituents (AMP, betaine, cysteine, succinate, and taurine) were measured using an antennular flicking assay. The rate of flicking increases with dose and has low thresholds: flick rates towards each of the five chemicals increased with concentration with thresholds between 1 nM and 100 microM. A mixed receptor composition model, which incorporates knowledge of the composition of receptor site types and their distribution across receptor cells (15), was used to predict responses to binary mixtures based on responses to the individual constituents. Nine of the ten binary mixtures elicited response magnitudes which were less than predicted by this model, suggesting mixture suppression. These mixture interactions appear to be independent of the concentration of the mixture tested; rather, they occur with the same magnitude at all concentrations. These behavioral results corroborate findings in olfactory receptor cell studies which indicate the significant prevalence of mixture suppression towards some of the same binary mixtures (19,20).