A revision of (Monogenea, Plectanocotylidae), with molecular barcoding of three species and the description of a new species from the streaked gurnard off Algeria.

Background: The family Plectanocotylidae includes parasites of the gills of marine fish; although nine genera and about 20 species have been described, almost no molecular information is available. Putting aside Diesing, 1850, supposedly a parasite of the white perch , never found again since its original description, two species were valid within Diesing, 1850 before this work: (Van Beneden & Hesse, 1863) Llewellyn, 1941 and Boudaya, Neifar & Euzet, 2006.

Methods: In this paper, we describe the third species of the genus and perform a comparative morphological and molecular analysis of the three species and of (Euzet & Suriano, 1974) Mamaev, 1976. Host fishes were also barcoded (COI) for confirmation of host identifications.

Results: n. sp. is described from the gills of the streaked gurnard collected off Algeria. The species is compared with specimens of cf. (from ) from the same locality and and (both from the longfin gurnard ). Molecules from cf. could not be compared with from the type-host and type-locality and we kept the status of the Mediterranean specimens as pending. Algeria is a new geographic record for and . n. sp. is distinguished from the other species found in the Mediterranean by the measurements of clamps, number of testes, and COI sequences, with notable divergence (7.8-11.8%) from the other two species of the genus.

Discussion: We briefly present a list of currently known members of the family Plectanocotylidae, their biology and their hosts.