Molecular (cox1), geographical, and host record investigation of monogeneans Mazocraes australis (Mazocraeidae), Polylabris sillaginae, and P. australiensis (Microcotylidae)

Morphomolecular identification of Polylabris lingaoensis infecting the twobar Seabream (Acanthopagrus bifasciatus)

A total of 40 fish samples of the twobar seabream, Acanthopagrus bifasciatus (Sparidae), were collected from January to June 2023 in the Arabian Gulf (Saudi Arabia). Fish samples were surveyed for ectoparasitic taxa. This study revealed the presence of one monogenetic species in A. bifasciatus gills. Parasitic prevalence and the mean value of intensity were 32.5% and 10, respectively. This parasite species has all the morphological characteristics of Polylabris, a genus erected by Euzet and Cauwet, 1967 (Microcotylidae), and mostly resembles Polylabris lingaoensis Tingbao, Kritsky, and Jun, 2007 on the presence of follicular testes ranging between 6-8, two rows of parallel microcotylid clamps in the haptoral structure with 35-45 per each, the conical form of the male copulatory organ, as well as the absence of genital armature. Molecular identification of this Polylabris species was conducted through sequencing of the partial nuclear large subunit (28S) of the ribosomal RNA (rRNA) and the mitochondrial gene of cytochrome c oxidase subunit I (COI). 28S rRNA genetic sequences were found to be conserved across several Polylabris spp., whereas, COI sequences were found to be more informative even with intraspecific variation. Therefore, the isolation of P. lingaoensis, provided herein, represents its first report on a marine sparid fish from Saudi Arabia. Furthermore, the reported sequences are also new genetic data for P. lingaoensis. Our findings will serve as the basis for any future study on monogeneans in Saudi waters.

"Something old, something new, something borrowed, and the oioxeny is true": description of Plectanocotyle jeanloujustinei n. sp. (Polyopisthocotylea, Plectanocotylidae) from the MNHN Helminthology collection with novel molecular and morphological data for P. gurnardi (Van Beneden & Hesse, 1863) (sensu stricto) from Sweden

Natural history museums worldwide house billions of apposite specimens, offering the potential for cost-free parasitological datasets. Herein, we provide novel morphological and molecular data (28S and cox1) for the polyopisthocotylean Plectanocotyle gurnardi sensu stricto from the type-host Eutrigla gurnardus from Sweden based on newly collected specimens from the Northeast Atlantic, and specimen from T. Odhner's collections at the Swedish Museum of Natural History (Stockholm, Sweden). The newly generated 28S sequences of P. gurnardi from E. gurnardus from the Northeast Atlantic were identical to those from the Western Mediterranean, and nested in a single clade, suggesting the presence of a single species. A 28S sequences of P. gurnardi sensu stricto from Sweden and those from the U.K. (type locality for P. caudata) were identical; we confirm that P. caudata and P. gurnardi are conspecific and formally synonymize them. A single 28S sequence of Plectanocotyle sp. from Chelidonichthys lastoviza off France differed from P. gurnardi from the Northeast Atlantic by 3-4 % and from P. gurnardi from France by 3%. Plectanocotyle sp. ex C. lastoviza off France is clearly not P. gurnardi, suggesting an oioxenic specificity of P. gurnardi to E gurnardus. Careful re-examination of Plectanocotyle cf. gurnardi from C. lastoviza from the Western Mediterranean from the Helminthology collection of Muséum national d'Histoire naturelle (Paris, France) revealed that it differs from all congeners by morphometry (size of clamps, of terminal lappet and its hamuli and uncinuli, and size of atrial spines). The cox1 divergences between P. cf. gurnardi and P. major, P. lastovizae, and P. gurnardi sensu stricto were 10-11 %, 10-11 % and 8 % respectively, falling within the interspecific variations range. Plectanocotyle from the Mediterranean is described as a new species, P. jeanloujustinei n. sp. We apprise nomenclature problems in Plectanocotyle and consider P. elliptica a species inquirenda.