CERCARIA BUCEPHALOPSIS HAIMEANA (LACAZE-DUTHIERS, 1854) (DIGENEA - BUCEPHALIDAE) IN COCKLE, CARDIUM EDULE L. IN SOUTH WALES

Some variations in the percentage infection of the cockle, Cardium edule L., on Llanrhidian sands, South Wales with Cercaria bucephalopsis haimeana (Lacaze-Duthiers, 1854) are described. Vertical variations in percentage infection are related to the population density of the final hosts and the seasonal variation with the breeding cycle of the first intermediate host. Only spent adult cockles, over 18·0 mm long and one year old, are infected, the highest percentage infection occurring in three-year old cockles. A decline in the percentage infection in older cockles suggests an increase in the mortality of infected specimens together with an increase in resistance to infection with age. Medium-sized cockles have a higher percentage infection than smaller and larger cockles of the same age. The parasite causes a decrease in the host's shell growth rate but an improvement in the flesh yield. The possible reasons for the variations in percentage infection and the effect of the parasite on the host are discussed. © 1969 Taylor and Francis Group, LLC.