Diplectanid parasites of Lithognathus mormyrus (L.) (Teleostei: Sparidae) from the Mediterranean Sea, with the description of Lamellodiscus flagellatus n. sp. (Monogenea: Diplectanidae).

Species of Lamellodiscus Johnston & Tiegs, 1922 are described from the gills of Lithognathus mormyrus (Linnaeus) in the Mediterranean Sea. A new nomenclature for a male copulatory organ with two articulated pieces is proposed: the hollow piece is referred to as the penis and we propose the term 'vectis' for the entirely sclerotised piece. It is shown that L. verberis Euzet & Oliver, 1967 actually comprised two species, L. verberis (sensu stricto), which is redescribed based on both the type-material and new material from the type-locality off Sète (France) and from off Sfax (Tunisia), and L. flagellatus n. sp. The two species are distinguished by the shape of the male copulatory organ and vagina (penis lacking a thread-like extension and vaginal duct short in L. verberis, versus penis with a thread-like extension and vaginal duct long in L. flagellatus); the vectis is similar in both species. Access to new material of L. mormyri Euzet & Oliver, 1967 from the same host species also enabled a redescription of this species. The status of L. ignoratus Palombi, 1943, another species from Lithognathus mormyrus, is discussed. A possible scenario for the synxenic speciation of these congeneric parasites of L. mormyrus is proposed.