Chemosensory conditioning of Hermissenda crassicornis.

Bite-strike responses of Hermissenda crassicornis, elicited by chemosensory stimulation of the lips, were found to be modified when food extracts were paired with rotation-produced stimulation of the statocysts. Animals that received repeated pairings of an extract of 1 food (conditioned stimulus, CS) with rotation exhibited suppressed bite-strike responses to that food for up to 48 hr after training. This suppression was usually specific to the trained food and was pairing-specific as well. Discriminative conditioning was also demonstrated. Animals trained with 1 CS paired with rotation and a second CS that was unpaired (CS-) showed suppressed bite-strike responses to the first CS. The results demonstrate that Hermissenda can learn to avoid foods that reliably signal an aversive event and may allow an analysis of higher order conditioning phenomena.