Phenotypic plasticity of burrowing depth in the bivalve Macoma balthica : experimental evidence and general implications

Abstract

AbstractDepth of burrowing in bivalves presents the individual with a trade-off: burrowing more deeply increases safety against predators but shallow burrowing increases food intake. Large variation in burrowing depth exists both between and within species. This study investigated whether part of this variation in depth in the tellinid Macoma balthica can be attributed to phenotypic plasticity. A predatory crab and food availability were either offered or withheld in separate aquaria and the response in burrowing depth measured. Individuals burrowed more deeply in the presence of a crab but only to shallow depths in the presence of food. This suggests that individuals can assess their environment and subsequently make decisions on their burrowing depth.Phenotypic plasticity like this flexible anti-predation behaviour in M. balthica can have farranging effects. In the presence of predators burrowing depth increases, reducing energy uptake and subsequent growth and reproduction, whereas increased burrowing depths reduces mortality by predation, further affecting prey and predator population dynamics.