Chemotaxis in the nudibranch Hermissenda crassicornis: Does ingestive conditioning influence its behaviour in a Y-maze?

The nudibranch mollusc Hermissenda crassicornis can be cultured easily in the laboratory and has been used as a biomedical model for learning and memory studies. Cultured animals whose only prey was Tubularia crocea were tested for responses to other prey. Naive slugs were conditioned with six different diets and tested for behaviour in a Y-maze. H. crassicornis was able to detect chemotactically food items which it had never been in contact with (such as Pennaria), but it did not detect some of the conditioning diets (e.g. Metridium). At least three hydroid species induce a chemotactic behaviour in the slug. it is shown that ingestive conditioning does affect their response in single-choice and double-choice experiments. As food items other than cnidarians are also detected, it is likely that different kairomones are responsible for the nudibranch's behaviour.