ORIGINAL PAPER The Gyrodactylus (Monogenea, Gyrodactylidae) parasite fauna of freshwater sand gobies (Teleostei, Gobioidei) in their centre of endemism, with description of seven new species Maarten P. M. Vanhove & Alcibiades N. Economou & Stamatis Zogaris & Sofia Giakoumi & Davor Zanella & Filip A. M. Volckaert & Tine Huyse Received: 26 August 2013 /Accepted: 7 November 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract While Gobioidei comprises showcases of (adaptive) radiation, the scientific interest they yielded did not ensure full understanding of goby biodiversity. Even in a well-studied region like Europe, wide knowledge gaps re- main. Sand gobies represent one of the few clades whose monogenean parasites have been thoroughly studied. However, in the Balkans, part of the sand gobies' centre of endemism, these parasites were unstudied. We focus on Greek and Croatian freshwater gobies. From five sand goby species, the first parasites are reported, describing seven new Gyrodactylus species. Economidichthys pygmaeus harbours Gyrodactylus benedeni sp. n. and Gyrodactylus dorlodoti sp. n. Its congener E. trichonis hosts G. meelkopae sp. n. Knipowitschia milleri was found to host G. charon sp. n., K. thessala is infected by G. bios sp. n., and K. croatica by G. douglasadamsi sp. n. and G. hellemansi sp. n. Gyrodactylus bubyri was found on its type host K. caucasica . A diverse parasite fauna is expected for a region known for its biodiver- sity and endemism. The contribution of parasites to species richness in such hotspots is overlooked. The observed species richness per host is rather low compared to the better-studied eastern Atlantic sand gobies. Host vicariance is considered to mediate parasite specificity in this fauna. Some new flatworm species display unique morphological features, such as the remarkable size of the marginal hook sickle proper compared to its foot in the Economidichthys parasites, or a characteristically kinked marginal hook sickle in G. douglasadamsi sp. n. These features reflect their hosts' endemism in the Balkans. Introduction Parasites account for more than 50 % of the total species richness on this planet (Timm and Clauson 1987; Windsor 1998). Their common tendency of exploiting a single host species or infection site is a powerful driver of diversification (de Meeûs et al. 1998). Moreover, parasites are of consider- able importance in terms of biomass (Kuris et al. 2008), ecosystem function (Marcogliese 2004) and indicator species (Sures 2004; Palm and Rückert 2009). Studying the diversity and systematics of parasites helps to unravel the mechanisms underlying species richness, and will enrich our understanding of this diverse and highly important group of organisms (Brooks and McLennan 1993; Thompson 1999; Brooks and Hoberg 2001; Littlewood 2011). A promising approach to understand parasite biodiversity is the use of monogenean flatworms infecting closely related host fishes, in view of their M. P. M. Vanhove : F. A. M. Volckaert : T. Huyse Laboratory of Biodiversity and Evolutionary Genomics, Department of Biology, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium M. P. M. Vanhove : A. N. Economou : S. Zogaris : S. Giakoumi Institute of Marine Biological Resources and Inland Waters, Hellenic Centre for Marine Research, 46.7 km Athens-Sounio Avenue, PO Box 712, Anavyssos 190 13, Greece D. Zanella Department of Zoology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, HR-10000 Zagreb, Croatia T. Huyse Department of Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium Present Address: M. P. M. Vanhove (*) Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic e-mail: maarten.vanhove@bio.kuleuven.be Parasitol Res DOI 10.1007/s00436-013-3693-8