GENOTYPE-ENVIRONMENT INTERACTION EXPRESSED IN THE FORAGING BEHAVIOR 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, biweek ly, periods of calm and wave action simulated in a tidal aquarium. Bec ause the dogwhelks were reared under standard laboratory conditions, a ny behavioural differences among the experimental populations could re asonably be inferred to be linked to some genetically based mechanism. In order to forage, the dogwhelks had to leave a refugium, traverse e mpty 'habitat' and enter a patch of mussels serving as prey. Wave acti on markedly depressed foraging activity, increased foraging latency an d lowered the patch-residence-time index. Dogwhelks derived;from popul ations naturally occurring on shores exposed to wave action reduced th eir 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 interpretatio n was offered, linking the differential behavioural response to habita t-specific shell morphology, known to be heritable. According to this interpretation, all dogwhelks react similarly to the drag forces gener ated by wave action, but the relatively shorter-spired shells of expos ed-shore dogwhelks cause weaker resultant forces than the taller-spire d shells of sheltered-shore individuals. Consequently, exposed-shore d ogwhelks tolerate higher levels of wave action than sheltered-shore mo rphs before suppressing their foraging behaviour. As exposed-shore dog whelks have greater tenacity associated with relatively larger pedal a rea, the increased tolerance of wave action extends opportunities for foraging without incurring extra risk of dislodgement. The sheltered-s hore morphology, which imparts greater resistance to desiccation, coin cidentally increases drag and so makes dogwhelks more likely to seek r efuge during occasional periods of heavy wave action. Exposed- and she ltered-shore morphologies therefore represent genotype-environment int eraction that is apparently adaptive, in part, through its effect on f oraging behaviour.