The effect of parasitism by the trematode Cryptocotyle lingua (Creplin) on zonation and winter migration of the common periwinkle, Littorina littorea (L.)

Abstract

Analysis of eight monthly samples of Littorina littorea taken between November and June from a rocky shore in Nova Scotia showed that there were four basic component populations with new brood settling in January and June. The brood settled subtidally after which they migrated up the shore to attain their adult positions at the end of their first year. Various tests showed that the snails migrated down the beach in the winter, the peak of migration occurring in February.Examination of snails on the beach and in a tide-simulating machine showed that, during the winter, those infected with Cryptocotyle lingua migrated more slowly and to a lesser extent than the non-infected snails. There was also indication that parasitized snails occurred lower on the beach, this being also duplicated in the tide-simulating machine.Subtidal snails were larger than their intertidal counterparts, suggesting that immersion was a more important factor than temperature in snail growth.