Mitochondrial DNA variation of a natural population of Gyrodactylus thymalli (Monogenea) from the type locality River Hnilec, Slovakia

The monogenean flatworm Gyrodactylus thymalli (Žitňan, Helminthologia, 2:266–269, 1960) is considered a harmless ectoparasite on grayling ( Thymallus thymallus ). The species is closely related to G. salaris Malmberg, 1957 that causes severe gyrodactylosis on Atlantic salmon ( Salmo salar ) in many Norwegian rivers. In this paper, we study the mitochondrial diversity of a G. thymalli population from one of the type localities Hrable on River Hnilec, Slovakia. By sequencing parts of the mitochondrial NADH dehydrogenase subunit 5 gene, we detected three haplotypes that differ from each other by 2.1–4.1%. The haplotype HnilecI was found most common. Our data suggest that River Hnilec has been colonized independently at least three times with G. thymalli .