A New Species of Branchellion (Hirudinea: Piscicolidae) Parasitizing the Gills of Short-Tail Stingrays (Batoidea: Dasyatidae) from the West Pacific.

A new fish leech, sp. n., is described based on specimens parasitizing the gills of the short-tail stingray, (Hutton, 1875), collected from Japanese waters. The new species can be distinguished from other congeners by having: i) pulsating vesicles emerging from posterior base of branchiae, one pair per somite; ii) dorsal white spots, not arranged in longitudinal row; and iii) blackish body. A phylogenetic tree based on partial sequences of the mitochondrial cytochrome oxidase subunit I gene from the new species and other piscicolid worms showed that the new species is sister to Savigny, 1822. This is the first record of Savigny, 1822 from Japanese waters.