Question: Do clams from populations not exposed to a predator retain the ability to respond to that predator??Motivation: If maintaining the potential for phenotypic plasticity involves a significant cost. plasticity should be selected against in constant environments.Background: Clams of the species Macoma balthica (a burrowing bivalve) respond to shore crabs by burrowing deeper in the sediment. Norwegian M. balthica are not exposed to crabs naturally whereas Dutch M. balthica are naturally exposed to variable crab densities.Sites: Collection: the Balsfjord near Tromso, Norway, and the Wadden Sea near Harlingen, The Netherlands. Holding tanks: outdoor basins with a continuous flow of unfiltered water from the Wadden Sea.Method: We introduced a mixture of clams from both sites into experimental aquaria with a thick layer of sandy sediment. Twelve aquaria contained one shore crab; twelve had none. We measured burrowing depth 7 days after the start of each experiment.Result: Clams from the two sites show similar burrowing responses after exposure to predatory crabs, supporting the hypothesis that maintaining the potential for plasticity costs very little.</p
