The occurrence of a trematode larva in a population of Littorina saxatilis (Olivi)

Abstract

1. Annual fluctuations in the percentage of L. saxatilis infected by Cercaria ubiquitoides at Whitstable, Kent, are described.2. Females are consistently more frequently parasitized than males.3. At higher shore stations more L. saxatilis are parasitized than at lower shore stations.4. Possible reasons for the above phenomena are discussed together with the relationship between trematode infection and the reproductive activity of L. saxatilis.