A survey of the gill parasites of Epinephelus costae (Teleostei: Serranidae) was conducted between 2001 and 2005 in the Gulf of Gabès (Tunisia). Five new species of Diplectanidae (Monogenea) were collected, all belonging to Pseudorhabdosynochus Yamaguti, 1958: P. bouaini sp. n., P. dolicocolpos sp. n., P. enitsuji sp. n., P. sinediscus sp. n., and P. sosia sp. n. These five species differ from each other and from all described species of Pseudorhabdosynochus by the morphology and size of their sclerotized vagina. These diplectanids (except P. sinediscus) were also collected from the same host off Dakar in 1981 and 1989. The present paper includes the descriptions and taxonomic considerations of each of these species in addition to an amended diagnosis of Pseudorhabdosynochus. A key to the five new species parasitizing E. costae is provided. These five species are the first diplectanids described from E. costae.
Lamellodiscus dentexi Aljoshkina, 1984, a gill parasite of Dentex macrophthalmus (Bloch), is redescribed based on new material from the northwest coast of Africa (Senegal and Morocco). Three new species of Lamellodiscus Johnston et Tiegs, 1922 from D. macrophthalmus are described, Lamellodiscus toguebayei sp. n., L. vicinus sp. n., and L. triacies sp. n., all belonging to the ''ignoratus'' group. They can be distinguished from all other species of this group by the size and shape of male copulatory organ and sclerotised parts of the haptor. Considering the peculiar morphology of the male copulatory organ (long and thin tube) we propose to put together L. dentexi, L. virgula Euzet et Oliver, 1967 and L. obeliae Oliver, 1973 to form the ''elongatus'' type within the ''elegans'' group.
While investigating the parasites of several marine fishes from the Western Atlantic, the Southern Gulf of Mexico and Central America (Panama), the following monogenoidean species from the gills of gerreid fishes (Gerreidae) were found: Diplectanum gatunense sp. n. (Diplectanidae) and Octouncuhaptor eugerrei gen. et sp. n. (Dactylogyridae) in Eugerres brasilianus (Cuvier) from Gatun Lake in the Panama Canal Watershed, and Diplectanum mexicanum sp. n. in Diapterus rhombeus (Cuvier) from the coast of Campeche State, Mexico. New diplectanid species are distinguished from other species of the genus by the general morphology of the copulatory complex and by the shape of the anchors and bars on the haptor. Octouncuhaptor gen. n. is proposed for its new species having slightly overlapping gonads (testis posterodorsal to the ovary), a dextrolateral vaginal aperture, a copulatory complex consisting of a coiled male copulatory organ with counterclockwise rings with the base articulated to the accessory piece, 8 pairs of hooks and the absence of anchors and bars on haptor. Our analysis of morphological features of Diplectanum species on gerreids evidences that these parasites more closely resemble each other than the known species from sciaenids suggesting that split between gerreids and sciaenids resulted in parasite speciation.
A new monogcncan species, Pseudorhabdosynochus capurroi sp. n., is described from the gills of the black grouper, Mycteroperca bonaci (Poey) (Serranidae), from the Yucatan Peninsula, Mexico. The new species can be differentiated from all other known species of Pseudorhabdosynochus Yamaguti, 1958 by being the largest one recorded until now (1162-1535 pm body length). Moreover, the vagina of P. capurroi has a small funnel-shaped opening with a non sclerotized vesicle from which a fine sclerotized duct leads proximally to a sclerotized seminal receptacle, and the testis is bilobate. The squamodiscs have 14 to 16 rows of rods, of which 3 to 5 rows are closed.
Species of Rhamnocercinae Monaco, Wood et Mizelle, 1954 are gill parasites of sciaenid fishes (Perciformes). Seven are marine species (three in the western Atlantic and four in oriental Pacific) and one is a neotropical freshwater species (Rio Doce Basin, Brazil). While the status of the subfamily may be questioned, this assemblage of species is apparently supported by several shared apomorphic and plesiomorphic characters, such as: (1) peduncular spines with anterior and posterior roots; (2) haptor laterally expanded, armed with anchors (two pairs); bars (one ventral, two dorsal); 14 hooks and haptoral accessory spines; and (3) double (nested) tubes of the male copulatory organ (MCO), directed posteriorly with the genital pore lying posterior to the MCO. The phylogenetic hypothesis for the eight known species of this clade is: (Spinomatrix penteormos (Rhamnocercoides stichospinus, Rhamnocercoides menticirrhi) Rhamnocercus oliveri (Rhamnocercus rhamnocercus (Rhamnocercus stelliferi, Rhamnocercus bairdiella, Rhamnocercus margaritae)). This hypothesis indicates that Spinomatrix penteormos represents the sister group of all remaining rhamnocercines. The resulting phylogenetic sister-group relationships support the transfer of Rhamnocercus stichospinus Seamster et Wood, 1956 to Rhamnocercoides Luque et Iannacone, 1991 as Rhamnocercoides stichospinus (Seamster et Wood, 1956) n. comb.
Numerous specimens of Calydiscoides spp. from Lethrinus nebulosus and L. harak, and fewer specimens from L. lentjan, L. ravus and L. obsoletus, collected off New Caledonia, South Pacific, were examined. Three species of Calydiscoides were recognized. Calydiscoides difficilis (Yamaguti, 1953) Young, 1969 was generally the most abundant species on the five hosts. Specimens of C. difficilis were measured and compared to the type specimens (from Indonesia) and museum vouchers (from Australia and the Arabian Gulf). The morphology of the massive male copulatory organ and of haptoral sclerotized parts was similar, but specimens from the same host and from different hosts showed wide morphometric variations; it is concluded that C. difficilis has a high degree of variability, although the possibility of a species complex remains. Calydiscoides duplicostatus (Yamaguti, 1953) Young, 1969 was found on L. nebulosus, L. harak and L. lentjan; specimens were homogeneous in the three hosts and similar to the type specimens. Calydiscoides terpsichore sp. n. is described from L. nebulosus (type host) and L. harak and was uncommon in both fish. The new species, a member of the 'australis group', is characterized by its Y-shaped male copulatory organ, with the left branch bearing a trifurcated secondary branch. Lethrinus nebulosus and L. harak shared the 3 species of Calydiscoides studied here, a fact probably related with their close phylogenetic relationships. Among the 15 species of Lethrinus present in New Caledonia, 11 were examined and 9 species harboured 1-3 species of Calydiscoides each. Only 7 species of Calydiscoides were found, due to their stenoxenous specificity. Each species of Calydiscoides has 1 to 5 hosts.