Composition and diversity of helminth communities in eels Anguilla anguilla in the River Tiber: long-term changes and comparison with insular Europe

Most studies of helminth communities in the European eel Anguilla anguilla have been undertaken in the British Isles, and there are very few analyses of community composition and structure from continental Europe. To fill thi s gap and test the hypothesis that helminth communities in freshwater eels in the British Isles are not typical of those of continental Europe, helmin th communities of eels in the River Tiber below Rome were analysed by seaso n using data collected in 1980 and new data from 1996. The intestinal helmi nth communities in the Tiber eels were species poor and characterized by lo w diversity. Most eels harboured one or no parasite species and communities were heavily dominated by the acanthocephalan Acanthocephalus clavula. Int estinal helminth infracommunity richness and diversity did not differ betwe en seasons within a year or between the same seasons in 1980 and 1996, alth ough some changes in composition were apparent. Intestinal infracommunities from Tiber eels were very similar in characteristics to those analysed fro m the British Isles, and their temporal changes also showed close similarit ies to those reported from rivers in the UK. It seems likely therefore that conclusions derived from British studies can be applied to helminth commun ities of eels on the continent.