Two species of Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 (both new) and two species of Demidospermus Suriano, 1983 (one new) are reported from the gills of the catfish Auchenipterus nuchalis, popularly known as “mapará”, from the Tocantins River and tributaries, North Region of Brazil. Cosmetocleithrum berecae n. sp. differs from all other species presently known in the genus by the morphology of the anchors presenting an elongate shaft and short recurved point, a coiled male copulatory organ (MCO) with three rings, and an elongate slender accessory piece with a bifurcated distal end. Cosmetocleithrum nunani n. sp. differs from its congeners by the combination of the following features: (1) Ventral and dorsal anchors with moderately long curved shaft and short point; (2) Hooks with poorly developed thumb; (3) Hook pairs 5 and 6 similar to each other, but morphologically distinct from remaining hook pairs; and (4) MCO coiled, with approximately 1.5 rings. Demidospermus tocantinensis n. sp. is easily distinguished from other species of the genus by presenting an inverted-G-shaped MCO with a median knee-like expansion. Demidospermus osteomystax Tavernari, Takemoto, Lacerda & Pavanelli, 2010 is redescribed based on paratypes and specimens from the gills of A. nuchalis from the Tocantins River, a new host and locality records for this species. The monotypic Paracosmetocleithrum Acosta, Scholz, Blasco-Costa, Alves & Silva, 2017, the only other Neotropical genus reported in siluriforms besides Cosmetocleithrum with species presenting two ribbon-like projections on the posterior margin of the dorsal bar, is considered a junior subjective synonym of Cosmetocleithrum.

In the Amazon, the growing demand for fish has been boosting the expansion of fish farms. However, the intensification of cultivation can generate disequilibrium in the parasite-host environment, predisposing fish to parasitic infections. The objective of this study was to evaluate the community structure of metazoan parasites in cultivation systems of piauçu, Leporinus macrocephalus, in the state of Acre, Brazil. We examined 100 specimens from a semi-intensive cultivation system (earth tanks) and 100 from an extensive system (dams). Overall 66.5% of the hosts were parasitized. We collected 1,240 parasite specimens, classified in 15 metazoan taxa (10 monogenoidean, one digenean and four nematodes). The parasite prevalence was higher by Monogenoidea in the dams, and by Nematoda in the earth tanks. The parasitic indexes were, in general, low and varied among species. Monogeneoidea had higher values for quantitative and ecological descriptors of parasitism in the dams, while Nematoda had higher values in the earth tanks. A single species of Digenea was found in the dams, with low prevalence. No taxon was classified as central. In the dams, parasite abundance was correlated only with total fish length, while in the earth tanks, it was positively correlated with total length, weight and condition factor of fish. The endoparasite and ectoparasite infracommunities presented higher richness, dominance, diversity and evenness, respectively, in the earth tanks and in the dams. This is the first study of ecological descriptors of parasites of L. macrocephalus in the Amazon. KEYWORDS: diversity, Digenea, Monogenoidea, NematodaComunidade de metazoários parasitos de Leporinus macrocephalus (Characiformes: Anostomidae) em sistemas de cultivo no oeste da Amazônia, Brasil RESUMO Na Amazônia, a crescente demanda por pescado vem impulsionando a expansão da piscicultura. No entanto, a intensificação dos cultivos pode gerar desequilíbrio no sistema parasito-hospedeiro-ambiente, predispondo os peixes a infecções parasitárias. O objetivo deste estudo foi avaliar a estrutura das comunidades de metazoários parasitos de piauçu, Leporinus macrocephalus, em sistemas de cultivo no estado do Acre, Brasil. Foram coletados 200 peixes, sendo 100 espécimes de sistema de cultivo semi-intensivo em viveiro escavado e 100 de sistema extensivo em açude. Dos 200 hospedeiros analisados 66,5% estavam parasitados. Foram coletados 1.240 espécimes de metazoários, classificados em quinze espécies (10 de Monogenoidea, uma de Digenea e quatro de Nematoda). A prevalência de parasitismo por Monogenoidea foi maior em açude e por Nematoda em viveiro. De forma geral, os índices de parasitismo foram baixos e variaram entre as espécies, com maiores valores dos descritores quantitativos e ecológicos do parasitismo por Monogenoidea em açude e Nematoda em viveiro. A única espécie de Digenea foi encontrada em açude e com baixa prevalência. Nenhum táxon foi classificado como central. Nos açudes, a abundância parasitária foi correlacionada apenas com o comprimento...

From December 2006 to March 2008, 60 specimens of Paralichthys isosceles and 25 specimens of P. patagonicus were investigated for helminths. One hundred and sixty-nine digeneans were recovered and parasites were identified as juvenile didymozoids of two types. Torticaecum and Neotorticaecum were found in 48 of the 60 P. isosceles (80%) and 10 of the 25 P. patagonicus (40%). Torticaecum and Neotorticaecum are reported for the first time in fish in South America (Brazil), found in the Atlantic Ocean. Morphometrics and illustrations are presented.

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Se presenta una lista completa de las 432 especies de Cestoda que se han descrito y / o registrados en Brasil. Se distribuyen através de 15 órdenes y 36 familias; 50 especies no fueron identificadas y 9 se consideran species inquirenda. Entre los peces, Zungaro zungaro (Humboldt in Humboldt & Valenciennes, 1821) fue el hospedador que fue más parasitadas (con 18 especies de cestodos); entre los anfibios, fue Rhinella icterica Spix, 1824, con 3 especies; y entre los reptiles, fue Bothrops jararaca (Wied-Neuwied, 1824), con 7 especies. Entre las aves, Gallus gallus (Linnaeus, 1758) presentó el mayor numero de asociaciones con cestodos, de tal manera que 13 especies se han registrado en Brasil y teniendo en cuenta los mamíferos, Homo sapiens (Linnaeus, 1758) presentan 13 especies diferentes. Pocos representantes de estas especies de cestode se reportaran de invertebrados. El pequeño número de los helmintos parásitos descritos es probablemente debido al submuestreo de hospedadores potenciales, junto con el pequeño número de expertos en la taxonomía de los parásitos.

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Three new species of Urocleidoides Mizelle & Price, 1964 are described from the gills of characiform fishes in the Tocantins River and its tributaries. Urocleidoides boulengerellae sp. nov. is described from Boulengerella cuvieri (Spix & Agassiz, 1829) and differs from all its congeners by the dorsal bar with a long posteromedial projection; male copulatory organ with 2–3 counterclockwise rings and a base with a flange; an accessory piece comprising a robust Y-shaped unit and a sheath-like unit; and a highly sclerotized vaginal canal. Urocleidoides paratriangulus sp. nov., described from Psectrogaster amazonica Eigenmann & Eigenmann, 1889, Cyphocharax gouldingi Vari, 1992, Caenotropus labyrinthicus (Kner, 1858) and Mylesinus paucisquamatus Jégu & Santos, 1988, is most similar to Urocleidoides triangulus (Suriano, 1981) Rossin & Timi, 2016 based on the shape of the anchors and bars but differs from U. triangulus in the morphology of the projection of the dorsal bar, the number of rings of male copulatory organ, and by the smaller size of members of hook pairs 1 and 5 compared with those of the remaining pairs. Urocleidoides tocantinensis sp. nov. is easily distinguished from all other species of the genus by the morphology of the vagina, which present a vaginal vestibule with a membranous cap. Urocleidoides triangulus is reported from its type host in the Guandu River, state of Rio de Janeiro. The present study increases the number of Urocleidoides species to 37 recognized species that fit all the generic characters.

This study presents the helminthofauna of digenean parasites of Acestrorhynchus falcirostris in the state of Amazonas (Brazil). Eight species belonging to four families were recovered: Metacercariae of Austrodiplostomum compactum (Diplostomidae) and Clinostomum marginatum (Clinostomidae) and mature specimens of Bellumcorpus majus, Prosorhynchoides carvajali, Rhipidocotyle santanaensis (Bucephalidae); Prosthenhystera obesa (Callodistomidae); Genarchella genarchella (Derogenidae) and Phyllodistomum spatula (Gorgoderidae). Examining specimens belonging to the genus Bellumcorpus collected from A. falcirostris, were observed a great variation in the size and shape of testes, which also could be observed in the type specimens of Bellumcorpus majus and B. schubarti. Considering the similar morphology and morphometric characteristics of both species, in this paper B. schubarti is considered synonym of B. majus. Acestrorhynchus falcirostris is a new host records for all these species of digenean, except to A. compactum and C. marginatum. Prosorhynchoides carvajali is referred for the first time in Brazil.