First Ukrainian record of the invasive leech Helobdella europaea (Hirudinea: Glossiphoniidae) from an aquarium in Kharkiv: morphological variability and phylogenetic relationships

New information on the occurrence of Helobdella europaea Kutschera, 1987 was obtained. Four individuals assigned to this species were found in a private aquarium in Kharkiv. Helobdella europaea has not been recorded for Ukraine so far. The taxonomic identity of the leeches was confirmed by both a morphological examination and a molecular phylogenetic analysis based on all available cox1 sequences of Helobdella leeches. Helobdella europaea was found to have extremely low genetic diversity, which has been probably caused by the founder effect. The variability of the coloration pattern of H. europaea was documented and discussed in the light of its potential usefulness for identification. The species can invade local freshwater ecosystems as has been already happened elsewhere.