Genotype-Environment Interaction Expressed in the Foraging Behaviour of Dogwhelks, Nucella lapillus (L.), under Simulated Environmental Hazard

The foraging behaviour of sub-adult Nucella lapillus originating from different field populations, was monitored for ten alternating, biweekly, periods of calm and wave action simulated in a tidal aquarium. Because the dogwhelks were reared under standard laboratory conditions, any behavioural differences among the experimental populations could reasonably be inferred to be linked to some genetically based mechanism. In order to forage, the dogwhelks had to leave a refugium, traverse empty `habitat' and enter a patch of mussels serving as prey. Wave action markedly depressed foraging activity, increased foraging latency and lowered the patch-residence-time index. Dogwhelks derived from populations naturally occurring on shores exposed to wave action reduced their foraging activity less strongly than those derived from sheltered-shore populations, but geographical origin (Plymouth or Anglesey) had no significant influence on foraging behaviour. A simple interpretation was offered, linking the differential behavioural response to habitat-specific shell morphology, known to be heritable. According to this interpretation, all dogwhelks react similarly to the drag forces generated by wave action, but the relatively shorter-spired shells of exposed-shore dogwhelks cause weaker resultant forces than the taller-spired shells of sheltered-shore individuals. Consequently, exposed-shore dogwhelks tolerate higher levels of wave action than sheltered-shore morphs before suppressing their foraging behaviour. As exposed-shore dogwhelks have greater tenacity associated with relatively larger pedal area, the increased tolerance of wave action extends opportunities for foraging without incurring extra risk of dislodgement. The sheltered-shore morphology, which imparts greater resistance to desiccation, coincidentally increases drag and so makes dogwhelks more likely to seek refuge during occasional periods of heavy wave action. Exposed- and sheltered-shore morphologies therefore represent genotype-environment interaction that is apparently adaptive, in part, through its effect on foraging behaviour.