Strength of the Dogwhelk Nucella lapillus and the Winkle Littorina littorea from different Habitats

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Abstract
The static strength of the shells of dogwhelks and winkles from 3 populations with different exposure to wave action was related to shell height, shell mass and dry body mass. The dogwhelk shells from the sheltered site were stronger, mass for mass, than those from the very exposed site. The shells from the intermediate site were intermediate. The stronger dogwhelk shells, coming from a site where predation pressure is almost certainly intense, protected less body mass per unit shell mass than did shells from more exposed sites. The Hughes et Elner (1979) suggestion that sheltered-shore dogwhelks have stronger shells, at the same time incurring greater metabolic cost, was quantitatively confirmed. The winkle shells showed little difference between sites. The lack of difference between the winkles from different sites is probably explained by the greater gene flow, permitted by the winkle''s pelagic eggs and larvae, smoothing out interpopulation differences.