We report digeneans (Diplostomidae, Crassiphialinae) in the endangered freshwater fishes Valencia letourneuxi and Valencia robertae, endemics of Western Greece. Digenean metacercariae occurred in two forms in the abdominal cavity, excysted and encysted, the latter attached to the gonads, liver and alimentary tract. Parasites were, using morphological and molecular techniques, identified as two representatives of Crassiphialinae, specifically part of the Posthodiplostomum-Ornithodiplostomum clade. The spatial, seasonal, and age class variation in parasite prevalence was examined. Autumn parasite prevalence varied between the six populations sampled (18.2 to 100%). Seasonal prevalence at the two sites sampled quadannually peaked in autumn and reached its lowest value in spring; prevalence increased with size to 100% in young adult fish. We did not find a correlation between prevalence and host sex. Overall parasites' weight averaged 0.64% of the host's, while parasite weight increased with host weight. A comparison of relative condition and hepatosomatic and gonadosomatic indices of infected and metacercariae-free specimens showed that infection did not have a significant effect on host body condition and reproduction. Regarding the parasite's life cycle, planorbid gastropods are proposed as potential first intermediate hosts in view of the host's diet and occurrence data of molluscs in the ecosystem. This is the first record of a diplostomid digenean in valenciid fishes and of representatives of the Posthodiplostomum-Ornithodiplostomum clade in a native Greek freshwater fish. Our findings are discussed in conjunction to fish conservation interventions, since parasites may contribute to the decline of endangered species.

Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic

Division of Parasites and Vectors Department of Life Sciences The Natural History Museum Cromwell Road London SW7 5BD UK

Institute of Marine Biological Resources and Inland Waters Hellenic Centre for Marine Research 46 7 km Athinon Souniou Av P O Box 712 190 13 Anavyssos Greece

Institute of Marine Biological Resources and Inland Waters Hellenic Centre for Marine Research 46 7 km Athinon Souniou Av P O Box 712 190 13 Anavyssos Greece Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic Laboratory of Biodiversity and Evolutionary Genomics Department of Biology University of Leuven Ch Deberiotstraat 32 3000 Leuven Belgium Capacities for Biodiversity and Sustainable Development Operational Directorate Natural Environment Royal Belgian Institute of Natural Sciences Vautierstraat 29 1000 Brussels Belgium Centre for Environmental Sciences Research Group Zoology Biodiversity and Toxicology Hasselt University Agoralaan Gebouw D 3590 Diepenbeek Belgium

Zoological Society of London Regent's Park London NW1 4RY UK

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