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 this gap and test the hypothesis that helminth communities in freshwater eels in the British Isles are not typical of those of continental Europe, helminth communities of eels in the River Tiber below Rome were analysed by season using data collected in 1980 and new data from 1996. The intestinal helminth communities in the Tiber eels were species poor and characterized by low diversity. Most eels harboured one or no parasite species and communities were heavily dominated by the acanthocephalan Acanthocephalus clavula. Intestinal helminth infracommunity richness and diversity did not differ between seasons within a year or between the same seasons in 1980 and 1996, although some changes in composition were apparent. Intestinal infracommunities from Tiber eels were very similar in characteristics to those analysed from the British Isles, and their temporal changes also showed close similarities to those reported from rivers in the UK. It seems likely therefore that conclusions derived from British studies can be applied to helminth communities of eels on the continent.

The structuring process of the macroparasite community of an experimental population of cichlasoma urophthalmus through time

The structuring process of the macroparasite community of caged Cichlasoma urophthalmus was studied over time using sentinel fish. Three thousand uninfected cichlids were stocked in floating cages introduced into a quarry in which a wild population of the same species was present. Caged and wild cichlids were sampled monthly over 6 and 7 months, respectively. Seventeen macroparasite species were found in the wild C. urophthalmus population, ten of which were detected in the caged population after 6 months. Early infections were by those species that were more frequent and abundant in the wild population, while helminths with a low prevalence and abundance in the wild appeared later in the caged fish population. The results suggested that the structuring process of the macroparasite community of caged C. urophthalmus followed a predictable pattern, in which those species that were most frequent and abundant in the wild were the first to establish in sentinel fish.