CHEMICALLY-MEDIATED PREDATOR-RECOGNITION LEARNING IN A MARINE GASTROPOD

We performed laboratory experiments to examine whether short-term expo sure to predation threat increases the intensity of the escape respons e of juvenile whelks, Buccinum undatum L., when confronted with the pr edatory asteroid Leptasierias polaris (Muller & Troschel). In the firs t experiment, we exposed whelks for 4 days to brief encounters with se veral stimuli associated with predation threat, including contact with and odors of L. polaris and potential alarm signals from conspecifics . The responsiveness of predator-conditioned whelks increased signific antly during the first three days of conditioning. On the fourth day, predator-conditioned whelks displayed stronger responses to contact wi th L. polaris than whelks held under control conditions. The second ex periment involved exposing three groups of whelks for 30 minutes every hour, over a 6-hour period, to (i) the odors of L, polaris (predator group), (ii) the odors of L. polaris feeding on whelks and of alarmed conspecifics (predator-whelk group), or (iii) to untreated seawater (c ontrol group), respectively. Bioassays performed after the conditionin g period showed that responses were stronger for the predator-whelk gr oup than for the control group, but similar between the predator and c ontrol groups. Our results indicate that experience with predators can cause the development of escape responses in B. undatum and provide t he first experimental evidence of a learned antipredator behavior in a mollusc. Such a learning process may explain the increase in responsi veness to L. polaris of whelks in the Mingan Islands as they increase in size. The learning process being mediated by waterborne chemical cu es may allow whelks to obtain information on the risk of predation in their environment without leaving the safety of refuges. Odors from ag itated, injured or dead conspecifics being required in this chemically -mediated learning process may ensure that whelks only become responsi ve to dangerous asteroids. Further studies are needed to evaluate the importance of stimuli integration, including learning events, in media ting the behavioral processes of B, undatum and other aquatic inverteb rates.