Spinitectus asperus and Klossinemella iheringi , intestinal nematodes of Prochilodus lineatus (Pisces, Prochilodontidae) from the alluvial plain of the Middle Paraná River, Argentina.

Prochilodus lineatus has been considered an ecosystem engineer in the Neotropics given its influence on important ecosystem processes, and it is therefore relevant to understand their inter-specific relationships. The association of P. lineatus with parasitic helminths was studied in two isolated shallow lakes of the alluvial plain of the Middle Paraná River. Only two species of gastrointestinal nematodes were found: Spinitectus asperus (Cystidicolidae) and Klossinemella iheringi (Atractidae), with S. asperus having higher prevalence and mean intensity values. This is the first record of K. iheringi in the Middle Paraná River, Argentina, as well as the southernmost citation of S. asperus.

Parasitism influence on the hepato, splenosomatic and weight/length relation and relative condition factor of Prochilodus lineatus (Valenciennes, 1836) (Prochilodontidae) of the Upper Paraná River floodplain, Brazil.

One hundred and forty-nine specimens of Prochilodus lineatus (Valenciennes, 1836) were collected on the Upper Paraná River floodplain (Brazil) from February 2000 to June 2001. Both parasitized and unparasitized fish showed alometric growth. The parasitized fish presented relative condition factor (Kn) values that were significantly higher than those of the unparasitized fish. In the age classes with unparasitized fish, the mean relative condition factor was always lower. Starting from two years of age, the Kn values were higher in the parasitized hosts. The monogenean Rhinonastes pseudocapsaloideum, the copepod Gamispatulus sp. and the digenean Saccocoelioides magnorchis presented significant positive correlation between their abundance and the relative condition factor of the host. No species presented correlation between abundance and the hepatosomatic relation. The acanthocephalan Neoechinorhynchus curemai presented positive correlation and the metacercariae Tylodelphys sp. presented negative correlation between the splenosomatic relation and abundance of parasitism.

New species of Tereancistrum Kritsky, Thatcher & Kayton, 1980 (Monogenea: Dactylogyridae: Ancyrocephalinae) from the gills of Prochilodus lineatus (Osteichthyes: Prochilodontidae) from the upper Paraná River floodplain, Brazil.

Two new species of Tereancistrum Kritsky, Thatcher & Kayton, 1980 are described from the gills of Prochilodus lineatus (Prochilodontidae) collected from the upper Paraná River floodplain, Brazil. T. toksonum n. sp. is characterised by a slim ventral bar with a sclerotised membrane along the anterior margin. Another characteristic is the dorsal anchor with an elongated deep root. T. curimba n. sp. is similar to T. ornatus Kritsky, Thatcher & Kayton, 1980 but possesses a sclerotised structure between the accessory sclerites of the ventral anchors. Moreover, the accessory anchor sclerites of this new species are longer than those described for T. ornatus.

A New Species of Kritskyia (Dactylogyridae, Ancyrocephalinae) Parasite of Urinary Bladder of Prochilodus lineatus (Prochilodontidae, Characiformes) from the Floodplain of the High Paraná River, Brazil

A new species of Kritskyia inhabits the urinary bladder of the "curimba", Prochilodus lineatus in the floodplain of the high Paraná river. The new species resembles others members of Kritskyia in the following features: haptor lacking anchors and with 14 hooks marginal, posterior male copulatory organ non articulated with the accessory piece and vagina a sclerotized tube. However, it differs from the known species mainly by the shape of the copulatory complex. This is the third endoparasitic monogenean species reported from freshwater Neotropical fish