This work examined the possible preference of Saccocoelioides nanii Szidat, 1954 for the three major intestinal portions of Prochilodus argenteus Agassiz, 1829 and statistically evaluated whether the river water level dynamic interfered in the parasite's ecological parameters and in its transmission to the definitive host. One-hundred-fifty specimens of P. argenteus were collected in July, 2003 (dry season) and in January, 2004 (rainy season) in the upper São Francisco River, State of Minas Gerais, Brazil. Of the 150 hosts, 96 (64%) were parasitized by S. nanii. The mean intensity and abundance were 32.6 ± 34.8 and 20.8 ± 31.9, respectively, and the range of infection intensity was from 1 to 177. The abundance of S. nanii was higher in the middle intestine than in either the anterior or posterior portions. This selection could be evidence of niche restriction to facilitate mating. The proportion of non-pregnant specimens of S. nanii was higher in the dry season as well as the intensity and abundance. At least two hypotheses can be considered for elucidated this inference: the presence/absence or change in the quantity of some substance in the host body amending/inhibits the reproduction of the parasite or that non-pregnant specimens corresponds to newly recruited individuals who did not have time to reproduce.

Myxobolus franciscoi sp. nov. (Myxozoa: Myxosporea: Myxobolidae) is described from the "curimatá-pacú" fish, Prochilodus argenteus Spix & Agassiz, 1829 (Actinopterygii: Prochilodontidae) from the Upper São Francisco River, Brazil. This parasite forms whitish plasmodia (about 1 x 1 mm) that develop in the connective tissue of fins. The spores are more or less round in frontal view and ellipsoidal in lateral view, measuring 6.4 (6.0-6.9) µm in length, by 6.0 (5.8-6.4) µm in width and 3.2 µm in thickness. The polar capsules are very small, measuring about 2 µm in length by 1.5 µm in width and ending in a tapered anterior neck. The polar filament makes three turns in a plane at right angles with the longitudinal axis of the spore. Thorough comparisons with the remaining species of Myxobolus Bütschli, 1882 described from South American fish, as well as with almost all species of Myxobolus described so far, are provided. This paper also includes a revision of Myxobolus species from South American fish hosts.

This research aimed to investigate the ecological indexes of the helminths of the digestive system and coelom of Prochilodus argenteus Spix & Agassiz, 1829. A total of 150 specimens (53 males and 97 females) taken from the upper reaches of the São Francisco River in the municipality of Três Marias (18º12'32"S, 45º15'41"W), State of Minas Gerais, Brazil, were examined. The specimens were collected in July, 2003 and January, 2004. Ninety-eight fish (65.3%) were infected by at least one species of helminth. Five helminth species were found: one digenean, Saccocoelioides nanii Szidat, 1954; two Eucestoda, Valipora sp., and one undetermined metacestode; one nematode, Spinitectus asperus Travassos, Artigas & Pereira, 1928; and one acanthocephalan, Neoechinorhynchus prochilodorum Nickol & Thatcher, 1971. The sex of the host did not influence parasite indexes. The total length of the hosts influenced the abundance of S. nanii (r s = -0.21, p = 0.01) and the prevalence of the metacestode (r = -0.91, p = 0.01). Saccocoelioides nanii was the dominant species in the parasite fauna of P. argenteus. Saccocoelioides nanii, Valipora sp., S. asperus and N. prochilodorum are reported here for the first time in P. argenteus and their known distribution is expanded to the São Francisco River.

Três espécies de aves, dois anatídeos, Dendrocygna bicolor (Vieillot, 1816) (marreca-caneleira) e Netta peposaca (Vieillot, 1816) (marrecão) e um phalacrocoracídeo, Phalacrocorax brasilianus (Gmelin, 1789) (biguá) foram coletados em vários locais na Província da Planície Costeira e no Lago Guaíba, Estado do Rio Grande do Sul. O número de aves examinadas de cada espécie de hospedeiro, assim como os valores de prevalência e intensidade média de infecção foram: 33 D. bicolor, 3%, 1 helminto/hospedeiro; 20 N. peposaca 15%, 4,3 helmintos/hospedeiro e 47 P. brasilianus 2,1%, 1 helminto/hospedeiro. O espécime coletado no biguá e um dos espécimes, entre aqueles, coletados nos marrecões estavam na cloaca. Os outros espécimes coletados nos marrecões e o único espécime coletado nas marrecas-caneleiras, respectivamente, estavam na bolsa de Fabricius. Este é o primeiro registro de P. ovatus em biguás e em marrecões. A distribuição geográfica conhecida de P. ovatus é estendida para o sul do Brasil e para o Estado do Rio Grande do Sul.

Three species of birds, two anatids, Dendrocygna bicolor (Vieillot, 1816) (Fulvous Whistling Duck) and Netta peposaca (Vieillot, 1816) (Rosy-billed Pochard), and one phalacrocoracid, Phalacrocorax brasilianus (Gmelin, 1789) (Neotropical Cormorant) were collected from several localities in the Coastal Plain Province and in Lago Guaíba, State of Rio Grande do Sul. The number of birds examined of each host species with the respective values of prevalence and mean intensity of infection of P. ovatus were: 33 D. bicolor, 3%, 1 helminth/host; 20 N. peposaca 15%, 4.3 helminths/host, and 47 P. brasilianus 2.1%, 1 helminth/host. The single specimen collected from the Neotropical cormorants and one of the specimens collected from the rosy-billed pochards, were in the cloaca. The remaining specimens from the rosy-billed pochards and the single specimen from the fulvous whistling ducks were in the bursa of Fabricius. This is the first record of P. ovatus in Neotropical cormorants and rosy-billed pochards. The known geographical distribution of P. ovatus is extended to the southernmost State of Brazil, Rio Grande do Sul.

Os nematóides do gênero Syncuaria Gilbert, 1927 são parasitos de aves das ordens Pelecaniformes, Ciconiiformes e Podicipediformes. Onze espécies são consideradas válidas neste gênero, no entanto, somente duas, Syncuaria buckleyi (Ali, 1957) Wong, Anderson & Bartlett, 1986 e Syncuaria squamata (Linstow, 1883) Wong, Anderson & Bartlett, 1986 parasitam aves do gênero Phalacrocorax Brisson, 1760. Entre 1999 e 2003 foram coletados 47 biguás, Phalacrocorax brasilianus (Gmelin, 1789) no Lago Guaíba, Município de Guaíba, Rio Grande do Sul, Brasil. Oito destas aves estavam infectadas por S. squamata. A prevalência e a intensidade média de infecção na amostra foram de 8,5% (8 de 47) e 2,5 helmintos/hospedeiro, respectivamente. Esta comunicação amplia a distribuição geográfica conhecida dos helmintos do gênero Syncuaria para o Brasil.

The nematodes of the genus Syncuaria Gilbert, 1927 are parasites of birds of the orders Pelecaniformes, Ciconiiformes, and Podicipediformes. Eleven species are considered valid in this genus, however, two species, Syncuaria buckleyi (Ali, 1957) Wong, Anderson & Bartlett 1986 and Syncuaria squamata (Linstow, 1883) Wong, Anderson & Bartlett, 1986 are parasites of birds of the genus Phalacrocorax Brisson, 1760. Between 1999 and 2003, 47 Neotropical Cormorants, Phalacrocorax brasilianus (Gmelin, 1789) were collected at Lago Guaíba, Municipality of Guaíba, Rio Grande do Sul, Brazil. Eigth of these birds were infected with S. squamata. The prevalence and the mean intensity of infection were 8.5% (8 of 47) and 2.5 helminths/host, respectively. This communication extends the known geographical distribution of nematodes of the genus Syncuaria to Brazil.

O presente trabalho é parte de um estudo maior sobre a helmintofauna dos cormorões Neotropicais conhecidos no Brasil como biguás, Phalacrocorax brasilianus (Gmelin, 1789), particularmente, no Estado do Rio Grande do Sul. Os nematóides que foram encontrados soltos no proventrículo/ventrículo ou em grupos compostos por adultos de várias idades e larvas de vários estágios (L3 e L4), formando granulomas eosinofílicos tiveram prevalência de 100% em 47 biguás do Lago Guaíba, Município de Guaíba. A morfologia dos lábios e dos interlábios, o padrão de distribuição das papilas caudais em machos examinados com microscópio eletrônico de varredura (MEV) e as extremidades dos espículos permitiram a determinação da espécie como Contracaecum rudolphii Hartwich, 1964 sensu lato (s. l.). Este é o primeiro registro de C. rudolphii na região Sul do Brasil.

The present report is part of a larger study on the helminth fauna of Neotropical Cormorants, Phalacrocorax brasilianus (Gmelin, 1789) in Brazil, particularly, in the southernmost State of Rio Grande do Sul. The nematodes which were found loose in the proventriculus/ventriculus or in groups of adults of different ages and of L3 and L4 larval stages, forming eosinophylic granulomas had a prevalence of 100% in 47 Neotropical cormorants from Lago Guaíba, Municipality of Guaíba. The morphology of the labia/interlabia, the distribution pattern of the caudal papillae in males examined under scanning electron microscopy (SEM), and the tips of the spicules allowed determination of the species as Contracaecum rudolphii Hartwich, 1964 sensu lato (s. l.). This is the first record of C. rudolphii in southern Brazil.

Uma nova espécie do gênero Andracantha Schmidt, 1975, parasita de biguás (cormorões neotropicais), Phalacrocorax brasilianus (Gmelin, 1789), é descrita e comparada com as outras seis espécies atualmente incluídas no gênero. A nova espécie difere das demais espécies previamente conhecidas de Andracantha por ter duas inflações na região anterior do corpo e por ter testículos em tandem na região central do corpo. Estas diferenças também são responsáveis pela emenda na diagnose do gênero agora proposta. Pela primeira vez é documentada a pigmentação alaranjada de acantocéfalos recém coletados do intestino, em qualquer espécie do gênero. Este é o primeiro registro de espécimes adultos do gênero Andracantha na América do Sul.

A new species of the genus Andracantha Schmidt, 1975, parasite of Neotropical cormorants, Phalacrocorax brasilianus (Gmelin, 1789), is described and compared to the other six species currently placed in the genus. The new species differs from the previously known species of Andracantha by having two inflations in the anterior region of the trunk and by having the testes in tandem in the central region of the body. These differences were also responsible for the diagnosis emendation of the genus now proposed. The orange pigmentation of the acanthocephalans recently collected from the intestine is documented for the first time in a species of this genus. This is the first record of adult specimens of any species of Andracantha in South America.