Pseudorhabdosynochus regius
Pseudorhabdosynochus regius is a diplectanid monogenean parasitic on the gills of the mottled grouper ("Mycteroperca rubra"). Description. "Pseudorhabdosynochus regius" is a small monogenean, about 600-1300 µm in length. The species has the general characteristics of other species of "Pseudorhabdosynochus", with a flat body and a posterior haptor, which is the organ by which the monogenean attaches itself to the gill of is host. The haptor bears two squamodiscs, one ventral and one dorsal, which are small, with a length of 20-40 µm, and made up of only 10-11 rows of rodlets. The sclerotized male copulatory  organ, or "quadriloculate organ", has the shape of a bean with four internal chambers, as in other species of "Pseudorhabdosynochus". The vagina includes a sclerotized part, which is a complex structure, 26-35 µm in length. It exhibits a trumpet in continuity with the primary canal, a straight primary canal, and primary and secondary chambers included in a common sclerotised mass along the primary canal. The sclerotised vagina is the structure used by systematicians to differentiate species of "Pseudorhabdosynochus". The closest relatives of "P. regius", based on the structure of its sclerotised vagina, are species mostly found in the Mediterranean  Sea and parasites on species of "Mycteroperca". Hosts and localities. The type-host of "Pseudorhabdosynochus regius" is the grouper mottled grouper ("Mycteroperca rubra") and the species has not been found in another host. The type-locality if off Dakar, Senegal. The monogenean has also been found on fish of the same species caught off Sfax, Tunisia and off Tripoli, Libya. Thus, "P. regius" is known from the Mediterranean Sea and the Eastern Atlantic. Only 14 species of diplectanids parasitic on groupers are known in the Mediterranean Sea and "P. regius" is one of them.