Seventy-four genera comprising approximately 140 named and 75 undetermined species of adult and larval nematodes are associated with about 330 named and 50 undetermined species of marine, brackish and freshwater fishes from Brazilian waters. These are listed with information on their hosts, habitat, distribution and records. A key to these parasites at the generic level is provided.

This study aimed to evaluate the community structure of metazoan parasites of Trichiurus lepturus from Ubatuba, Brazil. Fifty fish were collected in February 2008. Our statistical approach consisted in evidencing the most interesting infrapopulations, in order to try to understand the relationship between the variables regulating them. This analysis was based on a Poisson generalized linear model (GLM) developed with selection of variables using the corrected Akaike Information Criterion (AICc) and AIC weight. Larvae of Anisakidae and Lecithochirium microstomum seems to play an important role on this hostparasite system and their abundances were influenced by the ontogenetic shift in feeding of the hosts. Changes in characteristics of hosts included a negative relationship between increased abundance of anisakids' larvae and reduction in host weight. Gender biases were statistically consistent, but further long-term research is required to confirm them. Finally, we show the challenges that may be addressed in future research.

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During a survey conducted in the Lajeado Reservoir of the Tocantins River, in the state of Tocantins, Brazil, dactylogyrids were recovered from the gills of Pimelodina flavipinnis. Initial morphological analysis showed these dactylogyrids shared aspects of character with species of Demidospermus, with affinity to Demidospermus pinirampi, despite exhibiting differences with the original description by Kritsky et al. (1987) regarding the vagina, the base of the male copulatory organ and the shape and length of the bars. The analysis of the holotypes of D. pinirampi and its most morphologically close species, Demidospermus luckyi, revealed that these dactylogyrids were indeed D. pinirampi. This study therefore reports a new host and locality of occurrence, and reviews some measurements of the original description, supplementing and enhancing the morphological diagnosis of D. pinirampi. KEYWORDS: South America, Tocantins, morphology, parasite, Pimelodidae Descrição taxonômica complementar de Demidospermus pinirampi (Monogenoidea, Dactylogyridae), com registro de um novo hospedeiro e ampliação de sua área de distribuição RESUMO Durante um levantamento realizado no Reservatório de Lajeado, no Rio Tocantins, no estado de Tocantins, Brasil, dactilogirídeos foram recuperados das brânquias de Pimelodina flavipinnis. A análise morfológica inicial mostrou que esses dactilogirídeos compartilham aspectos de caráter com espécies de Demidospermus, com afinidade com Demidospermus pinirampi, apesar de apresentarem diferenças em relação à descrição original fornecida por Kritsky et al. (1987) com respeito à vagina, à base do órgão copulatório masculino e à forma e comprimento das barras. A análise dos holótipos de D. pinirampi e de sua espécie morfologicamente mais próxima, Demidospermus luckyi, revelou que estes dactilogirídeos eram realmente D. pinirampi. Este estudo, portanto, relata um novo hospedeiro e localidade de ocorrência e revisa algumas medidas da descrição original, complementando a diagnose morfológica de D. pinirampi.

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During a survey conducted in the Cuiabá and Paraguay Rivers in the Brazilian Pantanal wetland, in the states of Mato Grosso and Mato Grosso do Sul, we found branchiurans associated with Pseudoplatystoma reticulatum, Pseudoplatystoma corruscans, Salminus brasiliensis and Zungaro zungaro. These branchiurans correspond to Argulus chiropteroideus sp. n., Argulus multicolor, Argulus nattereri, Argulus pestifer, Dolops carvalhoi and Dolops longicauda. Besides the description of the new species, in this study we also provide important morphological notes for diagnosis of the other species. Specimens of Argulus chiropteroideus sp. n. were collected from skin of P. reticulatum and P. corruscans. They differ from A. multicolor and Argulus chicomendesi, in the shape of the postantennal spines, which is medially convex and has two lateral and one anterior stout tips in the new species, and for having three claviform, digitate spines on the base of the second maxillae (absent in A. multicolor; three conical, short spines in A. chicomendesi). A. chiropteroideus sp. n. do not have an anterior and a posterior spine on first two segments of first antenna, as well as no flagellum on the dorsal surface of the first two pairs of legs, structures present in A. multicolor and A. chicomendesi. The new species also differ from A. multicolor and A. chicomendesi, in the shape and number of sclerites that compound the support rods of the suction cup.

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