Abstract
Diplectanid monogeneans are gill parasites that can infect fish in huge numbers and thus become harmful, especially in maricultured fish. It is therefore useful to have taxonomic tools, such as keys, to identify species. The following diplectanid species from groupers of the Mediterranean Sea were studied: five species of Pseudorhabdosynochus Yamaguti, 1958, including P. riouxi (Oliver, 1986) Kritsky & Beverley-Burton, 1986 from the dusky grouper Mycteroperca marginata, P. enitsuji Neifar & Euzet, 2007, P. bouaini Neifar & Euzet, 2007, P. dolicocolpos Neifar & Euzet, 2007 and P. sinediscus Neifar & Euzet, 2007 from the goldblotch grouper M. costae, and Echinoplectanum echinophallus (Euzet & Oliver, 1965) Justine & Euzet, 2006 from the dusky grouper. New material was obtained from fish collected from off Tunisia and Libya and compared to the type-material and voucher specimens in museum collections. Identifications of fish were confirmed by barcoding of cytochrome c oxidase subunit I (COI) sequences. The sclerotized vagina was considered the most important structure for systematics. The three species P. riouxi, P. bouaini, and P. enitsuji share a common general structure of the sclerotized vagina with a conspicuous spherical secondary chamber. We thus propose the ‘Pseudorhabdosynochus riouxi group’ to accommodate them. Pseudorhabdosynochus dolicocolpos has an elongate vaginal structure that is completely different from all its congeneric species reported from the Mediterranean Sea, and Pseudorhabdosynochus sinediscus has a sclerotized vagina in which the secondary chamber is not visible, and a haptor without squamodiscs. A taxonomic key to diplectanid species on Mycteroperca spp. in the Mediterranean Sea is proposed; it includes ten species of Pseudorhabdosynochus and one species of Echinoplectanum.
Highlights
Diplectanid monogeneans are ectoparasites on the gills of fish, generally smaller than 1 mm, but often present in high numbers, even on wild fish
On the basis of type-material and specimens newly collected from off Tunisia. Other localities: Off Zarzis (Tunisia) and Libya (North Africa), we found that P. riouxi, P. bouaini, and P. enitsuji are morphologically close
Molecular identification of fish via DNA barcoding: The c oxidase subunit I (COI) sequences from three specimens from off Tunisia (Table 1) were already identified and published as M. marginata: KX255749 [22], KU739519, and KU739521 [31]
Summary
Diplectanid monogeneans are ectoparasites on the gills of fish, generally smaller than 1 mm, but often present in high numbers, even on wild fish. It is important to provide taxonomic identification keys to parasite species, which are currently lacking for diplectanids from groupers in the Mediterranean Sea. Diplectanids from groupers are currently classified into four genera [12]: mostly Pseudorhabdosynochus Yamaguti, 1958, with about eighty described species and, with a much smaller number of species, Laticola Yang et al, 2006 [13,14,15], Echinoplectanum Justine & Euzet, 2006 [16] and Diplectanum Diesing, 1858 [14, 17,18,19,20]. For fish identifications by barcoding, the Cytochrome c Oxidase subunit I (COI) sequences from our sampled specimens were compared with other COI sequences from different geographical regions published in GenBank; sequences and detailed comparisons were previously published [22, 31, 32]
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