The Genus Gyrodactylus von Nordman, 1832 (Monopisthocotyla: Gyrodactylidae) from Freshwater Fishes in Bulgaria: A Museum-Based Revision

The species composition and host–parasite associations of Gyrodactylus parasitising freshwater fishes in Bulgaria were re-examined based on the revision of museum specimens. Revised data are provided for 28 species. There are 22 species confirmed as occurring in Bulgaria based on morphological examination (G. aphyae, G. cyprini, G. fossilis, G. gobii, G. gracilihamatus, G. katharineri, G. laevis, G. latus, G. leucisci, G. luciopercae, G. macrocornis, G. macronychus, G. malmbergi, G. markakulensis, G. medius, G. prostae, G. rhodei, G. shulmani, G. sprostonae, G. stankovici, G. truttae and G. vimbi). New records for the country are reported for G. cobitis, G. dykovae, G. gobiensis and G. papernai. The data about the occurrence of nine species could not be verified. The most species-rich region is the Danube Drainage (21 species), followed by the East-Aegean Sea Drainage (12 species). The smaller drainages (Black Sea Drainage—nine species; West-Aegean Sea Drainage—four species) are less studied. G. prostae (four host species from eight localities) and G. sprostonae (four host species, four localities) are revealed as the most frequent species; these euryxenous parasites infect a broad range of host species, often fishes of economic importance. Fish species of less commercial value are less studied.