Redescription and Molecular Characterization of Freshwater Mussel-Associated Leech Hemiclepsis kasmiana (Hirudinea: Glossiphoniiformes: Glossiphoniidae)

Abstract

A freshwater mussel-associated leech, Hemiclepsis kasmiana Oka, 1910, is redescribed based on newly collected specimens from Japan, including its type localities. For the first time, the redescription provides morphological information on the internal digestive and reproductive systems of Japanese populations of H. kasmiana. Molecular phylogenetic analyses based on mitochondrial cytochrome c oxidase subunit I and nuclear 18S rRNA markers also reveal that H. kasmiana is most closely related to H. khankiana Bolotov, Klass, Bespalaya, Konopleva, Kondakov, and Vikhrev, 2019, and is not recovered as a monophyletic lineage with “H. kasmiana” from Korea and the Russian Far East, highlighting the necessity of re-evaluating the taxonomic status of continental populations of this species. In addition, DNA barcoding analysis of the crop contents of the present leech specimen indicates that freshwater fishes serve as primary hosts for H. kasmiana, consistent with observations of other mussel-associated congeners.