Through the lens of the taxonomist: combined morphological and molecular analysis in defining species of the genus Gyrodactylus

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Very little is known about the species richness and distribution of the genus Gyrodactylus von Nordmann, 1932 parasitising on spined loaches (Cobitidae) in Bulgaria and elsewhere. The only Bulgarian records to date are barely supported by morphological data and include the Bulgarian endemic G. matovi Ergens, Kakacheva-Avramova, 1966 and G. latus Bychowsky, 1933, both reported from Cobitis taenia Linnaeus, 1758. The controversy of these findings is amplified by the fact that recent ichthyological studies reveal that the reported host species is not present in Bulgaria but two other species of Cobitis inhabit Bulgarian rivers. The genus Sabanejewia Vladykov, 1929 has also been examined but has not been found to harbour any monogeneans. In an attempt to unravel their ectoparasitic fauna, spined loaches of the genera Cobitis and Sabanejewia were sampled from 11 rivers across the country, belonging to the Danube watershed and the Aegean Sea basins. The analysis of the collected monogeneans included a morphological examination of the haptoral hard parts and a molecular analysis of the ITS1-5.8S-ITS2 fragment of the ribosomal DNA. The results revealed one previously undescribed species for the genus Sabanejewia, one undescribed species parasitic on both Cobitis and Sabanejewia, one undescribed species from the genus Cobitis and the presence of G. latus, whose sequence is yet unpublished. All described parasites were collected from fish from different localities.