Cue association and antipredator behaviour in a pulmonate snail, Lymnaea stagnalis

Associative learning may help to offset costs of unnecessary escape behaviour by providing accurate information about the current risk to potential prey. We investigated innate antipredator behaviour and cue association learning in naïve gastropods. Juvenile laboratory-reared great pond snails, Lymnaea stagnalis (L.), were exposed to odour cues from a natural predator, tench, Tinca tinca (L.), and crushed conspecifics. The snails showed an innate antipredator behaviour to odour from T. tinca, by crawling above the water line (crawl-out response). This crawl-out response was significantly increased in the presence of alarm cues (crushed conspecifics). In a second experiment, juvenile L. stagnalis were exposed to tench odour and alarm cues in aquaria before being tested in behavioural assays. The behavioural responses to tench cue alone were similar to those seen in response to tench plus alarm cues presented together during the first experiment. Hence, L. stagnalis is apparently capable of relating potential predation risk to recent experience. In a final experiment snails were removed from pre-exposure cues for periods of 1, 4 and 8 days prior to behavioural assays. A raised level of avoidance persisted for at least 8 days, suggesting that this behaviour may be retained over timescales relevant to predation risk in the natural environment. The ability of organisms to modify antipredator behaviour based on recent experience, as found in L. stagnalis, would allow costs associated with unnecessary responses to be reduced while still allowing the organisms to avoid active predators.