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Bithynids snails are a widespread group of molluscs in European freshwater systems. However, not much information is available on trematode communities from molluscs of this family. Here, we investigate the trematode diversity of Bithynia tentaculata, based on molecular and morphological data. A total of 682 snails from the rivers Lippe and Rhine in North Rhine-Westphalia, Germany, and 121 B. tentaculata from Curonian Lagoon, Lithuania were screened for infections with digeneans. In total, B. tentaculata showed a trematode prevalence of 12.9% and 14%, respectively. The phylogenetic analyses based on 55 novel sequences for 36 isolates demonstrated a high diversity of digeneans. Analyses of the molecular and morphological data revealed a species-rich trematode fauna, comprising 20 species, belonging to ten families. Interestingly, the larval trematode community of B. tentaculata shows little overlap with the well-studied trematode fauna of lymnaeids and planorbids, and some of the detected species (Echinochasmus beleocephalus and E. coaxatus) constitute first records for B. tentaculata in Central Europe. Our study revealed an abundant, diverse and distinct trematode fauna in B. tentaculata, which highlights the need for further research on this so far understudied host–parasite system. Therefore, we might currently be underestimating the ecological roles of several parasite communities of non-pulmonate snail host families in European fresh waters. [ABSTRACT FROM AUTHOR]

The analysis of stable isotopes of carbon and nitrogen has been used as a fingerprint for understanding the trophic interactions of organisms. Most of these studies have been applied to free-living organisms, while parasites have largely been neglected. Studies dealing with parasites so far have assessed the carbon and nitrogen signatures in endoparasites or ectoparasites of different hosts, without showing general trends concerning the nutritional relationships within host–parasite associations. Moreover, in most cases such systems involved a single host and parasite species. The present study is therefore the first to detail the trophic interactions of a freshwater monogenean–host model using δ13C and δ15N, where a single monogenean species infects two distinctly different hosts. Host fishes, Labeobarbus aeneus and Labeobarbus kimberleyensis from the Vaal Dam, South Africa, were assessed for the monogenean parasite Paradiplozoon ichthyoxanthon , individuals of which were removed from the gills of the hosts. The parasites and host muscle samples were analysed for signatures of δ13C and δ15N using an elemental analyser connected to an isotope ratio mass spectrometer. Host fish appear to use partly different food sources, with L. aeneus having slightly elevated δ13C signatures compared to L. kimberleyensis , and showed only small differences with regard to their nitrogen signatures, suggesting that both species range on the same trophic level. Carbon and nitrogen signatures in P. ichthyoxanthon showed that the parasites mirrored the small differences in dietary carbon sources of the host but, according to δ15N signatures, the parasite ranged on a higher trophic level than the hosts. This relationship resembles predator–prey relationships and therefore suggests that P. ichthyoxanthon might act as a micropredator, similar to blood-sucking arthropods such as mites and fleas. [ABSTRACT FROM AUTHOR]

Between April 2003 and November 2006 a total of 191 individuals of the predominantly herbivorous fish species nase Chondrostoma nasus (L. 1758) were examined for parasites from six river sites in Austria. The following parasite taxa were recovered--Ciliata: Trichodina sp., Chilodonella piscicola, Ichthyophthirius multifiliis; Myxozoa: Myxobolus muelleri (cysts) and Myxobolus sp. (cysts); Monogenea: Dactylogyrus vistulae, D. chondrostomi and Dactylogyrus spp., Gyrodactylus sp., Diplozoon paradoxum; Digenea: Diplostomum spathaceum (larv.) and Tylodelphis clavata (larv.); Cestoda: Caryophyllaeus laticeps; Acanthocephala: Pomphorhynchus laevis; Bivalvia: Unio sp. (Glochidia); Crustacea: Lamproglena pulchella; Hirudinea: Piscicola geometra. The only taxa occurring at all sample sites were Dactylogyrus spp., which was also the dominant taxon at most sites, and Myxobolus muelleri, both from the gills of the fish. This is the first record of the parasite community of the nase in Austria.

In 2003, the parasite fauna of 197 European eels Anguilla anguilla, captured at three different locations (Laufenburg, Karlsruhe and Beneeden Leeuwen) in the River Rhine, was analysed. The eels harboured a total of 18 species, among them the protozoa (Myxidium giardi, Myxobolus kotlani and Trypanosoma granulosum), acanthocephalans (Acanthocephalus anguillae, Acanthocephalus lucii, Echinorhynchus truttae, Pomphorhynchus laevis), nematodes (Paraquimperia tenerrima, Pseudocapillaria tomentosa, Camallanus lacustris, Raphidascaris acus, Spinitectus inermis and Anguillicola crassus), cestodes (Bothriocephalus claviceps and Proteocephalus macrocephalus) and monogeneans (Pseudodactylogyrus sp.). The parasite fauna at the different locations is discussed with respect to the crustacean fauna present at these locations. The investigation shows that changes in the composition of the crustacean fauna, due to the anthropogenic breakdown of a biogeographic barrier, are reflected in the composition of the intestinal eel parasite fauna.