Parasite utilization of a host community: The distribution and occurrence of metacercarial cysts of Echinoparyphium recurvatum (Digenea: Echinostomatidae) in seven species of mollusc at Harting Pond, Sussex

The occurrence, in September 1979, of Echinoparyphium recurvatum metacercarial cysts in a community of molluscan hosts at Harting Pond, West Sussex, was investigated. The parasite exhibited broad host specificity with all 7 species comprising the molluscan community being infected. There were marked differences, however, in the extent to which each host species was utilized and using the mean number of parasites/ individual mollusc as a parameter of infection the mollusc species may be ranked in descending order of utilization as follows: Sphaerium corneum, Lymnaea peregra, Valvata piscinalis, planorbids, Pisidium subtruncatum and Potamopyrgus jenkinsi. Combination of basic infection data with population estimates for each mollusc species in the study area showed that the bivalve P. subtruncatum and the prosobranch V. piscinalis were the most important hosts because they contained approximately 90 % of the total number of cysts. In both of these hosts the cyst population was over-dispersed and the degree of over-dispersion increased with host size. The pattern of second intermediate host utilization is discussed in relation to the likely flow of E. recurvatum between the first intermediate host (L. peregra) and wildfowl definitive hosts at Harting.