Abstract
Monogenean parasites of Amur sleeper Perccottus glenii introduced to Europe during the last century were studied during two seasons in the Wloclawski Reservoir (Poland). Introduction of a single species Gyrodactylus perccotti with its host was confirmed in both seasons: autumn 2006 and spring 2008. Occurrence of G. perccotti in Europe was reported for the first time. Intensity of infection decreased from 2006 to 2008, but the prevalence did not differ between the seasons. G. perccotti sampled in autumn 2006 showed low morphometrical variability and high morphological similarity with parasites collected in host native range, Amur River. In contrary, high morphological and metrical variability was found within the samples collected in spring 2008. Nucleic acid sequencing of the partial ITS rDNA confirmed that despite the variation in morphology or size of haptoral hard parts, all studied Gyrodactylus specimens belonged to the same species (G. percotti) and no intraspecific variation was detected.