The life cycle of Magnivitellinum saltaensis n. sp. (Digenea: Alloglossidiidae) in Salta Province, Argentina.

We describe the alloglossiid trematode Magnivitellinum saltaensis n. sp., a parasite of the characiform fish Psalidodon endy, and its life cycle from Salta, northwest of Argentina. This is the first life cycle described for a species belonging to the genus Magnivitellinum. Cercariae emerged naturally from Biomphalaria tenagophila snails and infected experimentally exposed larvae of Diptera and Ephemeroptera as second intermediate hosts. These larvae in turn were exposed to commercially raised fish, and adults were recovered from characiform albino fish Gymnocorymbus ternetzi. Molecular analysis of natural and experimental adults showed the same genetic sequence for the partial region of 28S rDNA, thus confirming conspecificity. Comparison of these sequences with those published for M. simplex from Mexico showed 1.45% divergence, indicating that the specimens found in Salta belong to a different species, the third described of Magnivitellinum, in agreement with morphological data, geographical location, and host species composition. The new species is distinguished by its small body, vitelline follicles extending from the mid-level of the ventral sucker, Y-shaped excretory vesicle, and presence of papillae around the mouth.

The life cycle of Neocladocystis intestinalis (Vaz, 1932) (Digenea: Cryptogonimidae), in Aylacostoma chloroticum (Prosobranchia: Thiaridae), and Salminus brasiliensis (Characiformes: Characidae), in Argentina.

The life cycle of Neocladocystis intestinalis (Vaz, 1932) was resolved experimentally. The prosobranchiate snail Aylacostoma chloroticum Hylton Scott (Thiaridae) collected in the Yacyretá Dam, Province of Misiones, Argentina, was found naturally infected with cercariae that possessed pigmented eye spots, 7 pairs of penetration glands, 12 pairs of flame cells, and a V-shaped, or Y-shaped excretory vesicle with very short stem. The cercariae developed in oval cysts, which were found on fin rays, and under scales of naturally and experimentally exposed tetragonopterid fish species and of experimentally exposed poecilid and prochilodont fish species. Adults were obtained experimentally from juvenile Salminus brasiliensis (Characidae), bred in captivity, and infected with metacercariae from albino Gymnocorymbus ternetzi (Tetragonopteridae), which had been exposed to emerging cercariae.

Morphological and ITS2 Molecular Characterization of Ribeiroia Cercariae (Digenea: Psilostomidae) from Biomphalaria spp. (Gastropoda: Planorbidae) in Northern Argentina.

Species of Ribeiroia use planorbid snails as intermediate host. Since there is little information about these digenean parasites in South America, we aimed to assess whether Ribeiroia cercariae from 3 north Argentina locations belonged to the same species and differed from Ribeiroia cercariae described elsewhere. Specimens were obtained from Biomphalaria tenagophila and Biomphalaria orbignyi (Salta Province), and Biomphalaria occidentalis (Corrientes Province). Morphological traits of cercariae were analyzed, as well as their sequence of the ribosomal internal transcribed spacer 2 (ITS2). The ITS2 region consisted of 426 nucleotides identical in all samples, suggesting that all specimens belong to the same species in spite of their morphological differences and first intermediate host species. Comparison of the ITS2 region with GenBank database records showed that specimens from Argentina were different from Ribeiroia ondatrae (0.9% divergence), Ribeiroia marini (0.7% divergence), and Cercaria lileta (0.2% divergence). In summary, morphological, ecological, and ITS2 molecular data suggest that specimens from Argentina belong to a different species.

Keys to the species of Neolebouria Gibson, 1976 (Digenea: Opecoelidae: Plagioporinae), with a redescription of Neolebouria truncata (Linton, 1940).

Three keys to the species of Neolebouria Gibson, 1976, representing three body types, are provided based on the location of the genital pore relative to the intestinal bifurcation. These are: the lanceolata body type, where the genital pore is clearly prebifurcal; the diacopae body type, where the genital pore is located at or near the level of the intestinal bifurcation; and the maorum body type, where the genital pore is clearly postbifurcal. Fifteen species were assigned to the lanceolata body type; eight species to the diacopae body type; and four species to the maorum body type. Neolebouria truncata (Linton, 1940) is redescribed and N. georgiensis Gibson, 1976 is reinstated as a valid species. Neither N. georgiensis, nor N. antarctica Szidat & Graefe, 1967 (syn. Crassicutis antarcticus Szidat & Graefe, 1967), as described by Zdzitowiecki et al. (1993), represent N. antarctica, as originally described, and N. georgiensis and N. antarctica, as described by Zdzitowiecki et al. (1993), may be conspecific.

Redescription of Parspina argentinensis (Szidat, 1954) (Digenea: Cryptogonimidae) from freshwater fishes (Pimelodidae) in the basins of the Paraná and La Plata Rivers, Argentina, with comments on P. bagre Pearse, 1920.

The type-specimens of Parspina argentinensis (Szidat, 1954) from Pimelodus maculatus Lacépède, and new material from Iheringichthys labrosus (Lütken), Parapimelodus valenciennis (Lütken), Pimelodella gracilis (Valenciennes), Pimelodus albicans (Valenciennes), P. argenteus Perugia and P. maculatus caught in the basins of the La Plata and Paraná Rivers, Argentina, were studied to elucidate its taxonomic status. The type-specimens of Parspina bagre Pearse, 1920 from Pimelodella metae Eigenmann in Lake Valencia, Venezuela, were also studied and new observations on its morphology recorded. The amendation of the generic diagnosis of Parspina Pearse, 1920 is proposed based on the study of both species, which revealed, among other features, the absence of a thin walled-membrane enclosing the male terminal genitalia. Parspina argentinensis is characterised by the following features: absence of a gonotyl; presence of a bipartite seminal vesicle, pars prostatica and ejaculatory duct; caeca of nearly equal length; uterus extending from the level of the ventral sucker to end of body; testes symmetrical to slightly oblique; ovary transversely elongate, compact and variable in shape; and the utilisation of a wide range of freshwater fishes as hosts. The tegumental surface of this species is covered with pectinate spines arranged quincuncially. Spines decrease in size and density from forebody to hindbody. There are two types of sensory papillae, ciliated and dome-shaped. Ciliated papillae are distributed on the surface of the oral region and on the dorsal and ventral surfaces of the body, whereas dome-shaped papillae are found on the surface of the ventral rim of the oral sucker associated with a ciliated papilla. Gland-duct openings are interspersed with the spines of the oral crown. In addition, the infection indices of P. argentinensis vary widely, not only among different hosts but also between the Paraná and La Plata River basins. Higher prevalences of P. argentinensis are recorded in the La Plata River, and Pimelodus albicans, P. maculatus and Iheringichthys labrosus are the principal final hosts in this area.

Life cycle of Stephanoprora uruguayense (Digenea: Echinostomatidae) in Argentina.

The life cycle of Stephanoprora uruguayense Holcman et Olagüe, 1989, was experimentally resolved. In an artificial pond in the Zoological Garden in Buenos Aires City, Argentina, Heleobia parchappei (Hydrobiidae) was found to be releasing large-tailed cercariae with a prepharyngeal body, but lacking collar spines and corpuscles in the excretory system. Metacercariae, which encysted on the gills of naturally and experimentally infected Cnesterodon decemmaculatus (Poecilidae), developed collar spines and corpuscles in the excretory system in 7 days. Sexually mature adults were recovered from chicks and immature adults from mice fed metacercariae from C. decemmaculatus. Eggs shed in chick feces developed to miracidia within 10 days; sporocysts were found on the gills of snails. Stephanoprora uruguayense and S. denticulata from Europe are similar in adult morphology, but can be distinguished by morphological and behavioral features of larvae. Likewise, although S. denticulata and S. paradenticulata from Venezuela are similar to S. uruguayense in adult morphology, they differ considerably in larval morphology and intermediate hosts.

Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) in Galaxias maculatus (Osteichthyes: Galaxiidae) from Lake Moreno in Patagonia (Argentina).

Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) is described from the intestine of Galaxias maculatus (Osteichthyes: Galaxiidae) from Moreno Lake in Patagonia, Argentina. This species is distinguished from A. patagonicum Shimazu, Urawa & Coria, 2000, the other species recorded in the area, by its smaller body size, the diagonal position of the testes and different ratios of the suckers, testes and cirrus-sac in relation to body size. In addition, the synonymy of A. patagonicum with Polylekithum percai Ostrowski de Núñez, Brugni & Viozzi, 2000 is proposed herein.

Trematodes larvales de las familias diplostomidae, strigeidae y echinostomatidae en la Región Patagónica Argentina / Larval trematodes of diplostomidae, strigeidae and echinostomatidae in the Patagonian Region Argentina

Se describen tres cercarias pertenecientes a las familias diplostomidae, strigeidae y echinostomatidae (trematoda, digenea), emergidas de chilina sp (mollusca, gasteropoda) coleccionadas en el lago Escondido, Provincia de Río Negro, Argentina, entre enero 1987 y mayo de 1994