Developmental plasticity compensates for selected low levels of behavioural avoidance in a freshwater snail

The way in which an organism responds behaviourally to environmental stimuli may either be innate (i.e. expressed without the need for previous experience) or affected by prior experience; but the relative importance of these two mechanisms in controlling antipredator behaviour is, as yet, unclear. We investigated how the avoidance behaviour of juvenile great pond snails, Lymnaea stagnalis (L.), artificially selected for either high or low innate avoidance behaviour, where the snail crawls above the waterline in response to predation cues, differed in terms of their response to prolonged exposure to predator kairomones during their development. Specifically, we tested: (1) whether snails from lines selected for low response showed enhanced crawl-out behaviour following exposure to predator kairomones during development; and (2) whether snails from high-response lines were able to increase their response further when raised in predator kairomone or whether these snails were constrained in their response. Following developmental exposure to kairomones from a predatory fish (i.e. tench, Tinca tinca L.), low-response snails showed an increased avoidance response when exposed to predation (i.e. predator kairomone plus alarm cues), equivalent to that seen in lines selected for high innate responses. In contrast, snails from high-response selection lines showed no change in crawl-out behaviour. These findings suggest that for antipredator behaviour, developmental exposure can compensate for the selected reduction in innate response in L. stagnalis, and that there may be constraints limiting the maximum level of crawl-out behaviour.