Enhancement of the response of rock crabs, Cancer irroratus, to prey odors following feeding experience

The rock crab, Cancer irroratus Say, uses chemically mediated learning in the search for food. Rock crabs are opportunistic benthic predators and scavengers. Observations indicate that although they eat a variety of items, they are more sensitive to, and prefer, odors of food items that they have been eating. We found that C. irroratus is more responsive to a familiar food source than to an unfamiliar one and can distinguish between the odors of two different prey after being fed one species for an extended time. Initial preferences for two mytilid bivalves, Mytilus edulis and Geukensia demissa, were determined in a Y-maze. Crabs were then fed only one of the mussel species for 28 days and retested, using sequential and simultaneous presentations, for their responses to familiar and unfamiliar prey odors. Crabs increased their responses to familiar prey odors, but not to unfamiliar odors. In foraging tests, crabs ate M. edulis more often regardless of the species to which they had been familiarized.