Temporal variation in prevalence and cercarial development of Echinostephilla patellae (Digenea, Philophthalmidae) in the intertidal gastropod Patella vulgata

The trematode Echinostephilla patellae is an abundant but scarcely investigated parasite found in coastal ecosystems of the British Isles. Redial and cercarial stages of the digenean occur in the digestive gland and gonads of common limpets Patella vulgata. Here, we present data on the temporal distribution of E. patellae infections in P. vulgata from an intertidal site on the Irish south coast as well as on the intramolluscan development of the cercariae over a period of one year. Prevalence of infection showed temporal variation with a distinct peak in September, possibly related to an increase in the abundance of bird final hosts coinciding with comparatively high temperatures at the study locality during the summer months. Maturation of cercarial stages was strongly correlated with water temperature. Whilst fully developed cercariae were present in the rediae from May to November, large numbers of infective stages occurred in the limpets' mantle blood vessels - where they accumulate prior to release - between June and September, suggesting this period of time to be the main transmission window for E. patellae cercariae.