Molecular characterisation of the monogenea parasites of blue mackerel Scomber australasicus (Perciformes: Scombridae) in Australian waters

Assessment of the Genetic Diversity of the Monogenean Gill Parasite Lamellodiscus echeneis (Monogenea) Infecting Wild and Cage-Reared Populations of Sparus aurata (Teleostei) from the Mediterranean Sea

The diplectanid monogenean Lamellodiscus echeneis (Wagener, 1857) is a specific and common gill parasite of the gilthead seabream Sparus aurata Linnaeus, 1758, in the Mediterranean Sea. Few isolated molecular studies of this monogenean have been conducted, and its population structure and genetic diversity are poorly understood. This study represents the first analysis of the population genetics of L. echeneis, isolated from wild and cage-reared gilthead seabream from fifteen localities in both the Southern (Tunisia) and Northern (Italy and Spain) regions of the Mediterranean Sea, using nuclear ITS rDNA markers and a partial fragment of the mitochondrial gene cytochrome oxidase subunit I (COI). The phylogenetic trees based on the newly obtained dataset and the previously published sequences of L. echeneis corroborated the spread of only a single species throughout the Mediterranean Sea. The star-like haplotypes network, inferred by COI sequences, suggested a recent population expansion of L. echeneis. This is supported by the observed high haplotype diversity (Hd = 0.918) and low nucleotide diversity (Pi = 0.01595). Population structure-based AMOVA for two groups (the Adriatic Sea and the rest of the Mediterranean Sea) attributed 35.39% of the total variation to differences within populations, 16.63% to differences among populations within groups, and 47.99% to differences among groups. Fixation indices were significant, with a high FST value (0.64612), likely related to the divergence of the parasite populations from the Adriatic Sea and other Mediterranean regions. Phylogenetic analyses grouped all samples into the main clade corresponding to L. echeneis from several localities. This study provides insight into the genetic variation between L. echeneis populations, and did not show a clear genetic structure between populations of L. echeneis throughout Tunisian, Italian, and Spanish localities, which can be attributed to the considerable gene flow between the populations favoured by the potential for host dispersion within the Mediterranean Sea. Finally, haplotypes shared between wild and cage-reared hosts provided evidence for the potential for cross-infection between wild and farmed hosts in the Mediterranean Sea.

"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.