Behavioral resolution of quality of odorant mixtures by spiny lobsters: differential aversive conditioning of olfactory responses

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Abstract
A differential aversive associative conditioning paradigm was used to demonstrate the ability of spiny lobsters to discriminate behaviorally between four 41-component chemical mixtures. These mixtures were based on natural extracts of crab, mullet, oyster and shrimp. Previously, we demonstrated, using the same paradigm, that lobsters conditioned to avoid the shrimp mixture could discriminate, to varying degrees, between the shrimp mixture and the other three mixtures. The present study was performed to compare the perceived quality of all four mixtures. This was accomplished by conditioning four groups of animals, each group to a different mixture type, and then using multidimensional scaling (MDS) analysis to compare simultaneously the similarities and dissimilarities among the four mixtures as inferred by passive and active avoidance behaviors. These two types of behaviors revealed different aspects of the discrimination: greater differentiation of the conditioned mixture from the non-conditioned mixtures was indicated by active avoidance behavior, while gradations in the degree of discrimination between the conditioned mixture and each of the non-conditioned mixtures were indicated by passive avoidance behaviors. Overall, lobsters perceived crab and shnmp mixtures as being similar to one another and dissimilar to mullet and oyster mixtures, while they perceived mullet and oyster mixtures to be dissimilar to one another and to the crab and shrimp mixtures. Comparison of results from MDS analyses of behavioral mixture discrimination, neural mixture discrimination and mixture compositions may be used both to provide an indication of the type of neural coding used to make these behavioral discriminations and to identify the components of the mixtures that are responsible for recognition of and differential response to the mixtures.