Rhinoxenus (Dactylogyridae) parasitizing piranhas (Serrasalmidae) at its southernmost limit of distribution (Paraná River, Argentina), with the description of two new species.

Three piranha species, Serrasalmus maculatus, S. marginatus and Pygocentrus nattereri, living sympatrically in the lower Paraná River (Argentina) were examined searching for nasal monogeneans to know its diversity and distribution. Four species of monogeneans belonging to Rhinoxenus were found parasitizing the nasal cavities. Two new species are described, and new morphological data of 2 previously described species is provided. Rhinoxenus argentinensis n. sp. is characterized by having the male copulatory organ (MCO) as a coiled tube with a reel shaped-base; an elongated accessory piece articulated to base of MCO; a sinistral vagina with a sclerotized vestibule, and a sclerotized cap of the ventral anchor laterally modified forming a triangular expansion. Rhinoxenus paranaensis n. sp. is characterized by having a MCO as a coiled tube with a reel-shaped base; an accessory piece with an elongate proximal portion, a dilated distal portion with digitiform projections articulated to base of MCO; a sinistral vagina with 5-6 cuticular spine-shaped processes, and a sclerotized cap of the ventral anchor modified laterally forming a bilobate expansion. Additionally, multivariate discriminant analyses showed significant morphometric differences in the ventral anchors among Rhinoxenus species parasitizing 'piranhas '.

Diversity of Empruthotrema Johnston and Tiegs, 1992 parasitizing batoids (Chondrichthyes: Rajiformes and Myliobatiformes) from the Southwest Atlantic Ocean, with description of three new species.

During an extensive research project involving 519 specimens of batoids, including 13 species of Rajiformes and Myliobatiformes (Chondrichthyes) from the Argentine Sea, three new species of Empruthotrema were found and are described using morphologic characteristics and two molecular markers: LSU rDNA and COI mtDNA. The new species can be distinguished from their congeners by the number and distribution of the marginal loculi, the length and morphology of male copulatory organ, and the presence of eyespots. Additionally, multivariate analysis identified the dimensions of the pharynx and ejaculatory bulb as diagnostic features. Host specificity and previous records of the genus in the region are discussed. This is the first description of new species in this genus for the Southwestern Atlantic Ocean, as well as for arhynchobatid hosts.

Three-dimensional morphology of rigid structures as a tool for taxonomic studies of Dactylogyridae (Monogenea).

Dactylogyridae is overwhelmingly the most abundant and diverse taxon among monogeneans in continental waters of South America. Their small body size requires considerable sampling effort and training for collecting and identifying the worms from the gills, skin, nasal cavities, and other microhabitats. Indeed, diagnostic characteristics as sclerites and male copulatory complex are generally less than 100-µm long and are essential for taxonomic description and identification of species. Here, a combination of simple and routine methods for three-dimensional morphological studies on hard structures is proposed for dactylogirids: SDS treatment for clarification of specimens and enzymatic digestion with proteinase K for freeing sclerotized structures, followed by laser confocal microscopy. This method is applicable to fresh or fixed specimens and does not require staining or dehydration. Indeed, stable autofluorescence emission is detectable at 500-530 nm for bars, anchors, and male copulatory complex when excited by argon laser. Advantages of this protocol over previous methodologies for taking laser confocal images are discussed. Open access software for image processing was used for three-dimensional reconstruction of sclerotized structures generating models and full 360° rotation videos.

A new species of Neoascarophis (Nematoda: Cystidicolidae) parasitic in Macrourus carinatus (Macrouridae) from Argentinean waters.

Nematodes of the cystidicolid Neoascarophis Machida, 1976 , are all parasites of macrourid fishes, making up at present 5 species. Several other unidentified species have also been reported in several fish species from the northern and southern Atlantic Ocean, including 1 from Macrourus carinatus (Günther) (Macrouridae) in the southwest Atlantic Ocean. During a parasitological survey carried out on samples of M. carinatus from Patagonian waters, nematodes referable to Neascarophis were found in ulcers in the gastric mucosa. These nematodes Neascarophis sphaerocaudata n. sp. closely resemble N. macrouri by the posterior position of the vulva and the dilated posterior extremity in females. However, the new species differs from N. macrouri mainly by its larger size, a larger muscular esophagus, and a widely globose posterior extremity in females. SEM study of cephalic structures also showed morphological differences between both species, especially in the morphology of the submedian labia and lateral pseudolabia. In view of these differences a new species is proposed.

A new species of Capillostrongyloides (Nematoda: Capillariidae) parasitizing the horsefish, Congiopodus peruvianus (Pisces: Congiopodidae), from Argentina.

A new species of parasitic nematode, Capillostrongyloides congiopodi n. sp. (Capillariidae), is described based on specimens collected from the gall bladder of the horsefish, Congiopodus peruvianus Cuvier and Velenciennes (Congiopodidae, Scorpaeniformes), from the Patagonian Shelf, Argentina (45-48 degrees S; 60-64 degrees W). Among the 9 species described so far in the genus, the new species most closely resembles C. norvegica Moravec and Karlsbakk, 2000, by the presence of its conspicuously elevated anterior vulvar lip in females; however, it is readily distinguished from it by having a larger body size, larger eggs with protruding polar plugs, the shape and length of the spicule, and mainly by the general morphology of the caudal bursa of males. In addition, the site of infection, i.e., stomach versus gall bladder. This is the first Capillostrongyloides species reported from fishes in the southern Atlantic Ocean.

A new species of Paracapillaria (Nematoda: Capillariidae) parasitizing the Brazilian sandperch, Pinguipes brasilianus (Pisces: Pinguipedidae), from Argentina.

A new species, Paracapillaria argentinensis n. sp., is described from the pinguipedid fish Pinguipes brasilianus Cuvier, 1829 from waters off Mar del Plata, Argentina (38 degrees 08'S, 57 degrees 32'W) (prevalence 22.2%; mean intensity +/- SD, 4.42 +/- 5.19). The new species is assigned to the subgenus Paracapillaria Moravec, 1987. Of the 10 species so far known in the subgenus, the new species more closely resembles P. (P.) plectroplites, from which it is distinguished by having a spicule with an expanded anterior end and a slender medial section. A similar spicular morphology is observed in P. (P.) epinephell; however, it shows shorter spicules and a highly reduced caudal bursa. This is the first record of Paracapillaria in the southwestern Atlantic Ocean.

A new species of Capillaria (Nematoda: Capillariidae) parasitizing Conger orbignianus (Pisces: Congridae) from Argentina.

Capillaria (Procapillaria) navoneae n. sp. is described from the congrid fish Conger orbignianus from waters off Mar del Plata, Argentina (38 degrees 08'S, 57 degrees 32'W) (prevalence 29.17%, mean intensity +/- SD 6.07 +/- 6.59). The new species is assigned to the subgenus Procapillaria Moravec, 1987, despite the absence of vulvar appendages in gravid females. Of the 3 species so far known in the subgenus, the new one most closely resembles C. (P.) margolisi, from which it is distinguished by lacking a medial expansion in the spicule and a slightly elevated anterior lip of vulva, and by having a shorter esophagus, a larger number of stichocytes, and a shorter tail.