A revision of Plectanocotyle (Monogenea, Plectanocotylidae), with molecular barcoding of three species and the description of a new species from the streaked gurnard Chelidonichthys lastoviza 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 Plectanocotyle elliptica Diesing, 1850, supposedly a parasite of the white perch Morone americana, never found again since its original description, two species were valid within Plectanocotyle Diesing, 1850 before this work: Plectanocotyle gurnardi (Van Beneden & Hesse, 1863) Llewellyn, 1941 and Plectanocotyle major Boudaya, Neifar & Euzet, 2006. Methods: In this paper, we describe the third species of the genus Plectanocotyle and perform a comparative morphological and molecular analysis of the three species and of Triglicola obscura (Euzet & Suriano, 1974) Mamaev, 1976. Host fishes were also barcoded (COI) for confirmation of host identifications. Results: Plectanocotyle lastovizae n. sp. is described from the gills of the streaked gurnard Chelidonichthys lastoviza collected off Algeria. The species is compared with specimens of Plectanocotyle cf. gurnardi (from C. lastoviza) from the same locality and P. major and T. obscura (both from the longfin gurnard C. obscurus). Molecules from Plectanocotyle cf. gurnardi could not be compared with P. gurnardi 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 P. major and T. obscura. Plectanocotyle lastovizae 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.