THE RELATIONSHIP BETWEEN SHELL INJURIES, SHELL THICKNESS AND HABITAT CHARACTERISTICS OF THE INTERTIDAL SNAIL LITTORINA RUDIS MATON

The hypothesis that risk of shell injury from crab predationand crushing by boulders and stones is important in the selectionof shell thickness in the intertidal gastropod Littorina rudisMaton was tested using data from 24 populations from Britain.Although there was an obvious relationship between the incidenceof shell injuries and both the distribution of crabs and substratummobility, there was no correlation between risk of shell injuryand shell thickness. This is probably accounted for by between-habitatvariations in energy levels which may vary independently ofcrab density and substratum mobility. ^*Present address: Department of Biology, University of Essex,Wivenhoe Park, Colchester C04 3SQ (Received 23 May 1977;