Abstract Ten endoparasite species found in Pygocentrus piraya, which is a piranha species native to São Francisco river, were collected from 108 fish caught in Três Marias reservoir in 2004 and 2005, namely: Digenea - Austrodiplostomum sp. (metacercariae); Eucestoda – Proteocephalidae gen. sp. (plerocercoids); and Nematoda - Procamallanus (Spirocamallanus) inopinatus, Cystidicoloides fischeri and Capillostrongyloides sentinosa (adults); Spinitectus rodolphiheringi (juvenile); Hysterothylacium sp., Contracaecum sp. Type 1, Spiroxys sp. and Goezia sp. (larvae). In helminth fauna, P. (S.) inopinatus has shown higher prevalence and dominance. Fish sex has influenced the prevalence of Hysterothylacium sp., which was higher in female specimens. Longer total length of fish has positively influenced the abundance of C. sentinosa and Hysterothylacium sp.. The rainy season has favored parasitic indices, mainly P. (S.) inopinatus abundance, as well C. sentinosa and Hysterothylacium sp. prevalence and abundance. There were co-occurrences between adult and some larval nematodes. Endemic piranhas, as well as final hosts, are important intermediate and/or paratenic hosts, given the relevant number of larvae (proteocephalideans and nematodes) of heteroxene cycle found in them. Proteocephalidae gen. sp., C. sentinosa, Hysterothylacium sp., Contracaecum sp. Type 1, Goezia sp. and S. rodolphiheringi are new records parasitizing P. piraya in São Francisco basin.

Resumo A fauna endoparasitária de Acestrorhynchus lacustris de oito lagoas marginais da bacia do alto e médio rio São Francisco, Brasil, foi registrada pela primeira vez. Para isso, um total de 106 espécimes de A. lacustris foi coletado. Dezoito espécies de helmintos foram encontradas. Os táxons relacionados foram do Filo Platyhelminthes: uma metacercária de Clinostomum sp. (Trematoda: Clinostomidae); larvas plerocercoides de espécie não identificada (Eucestoda: Proteocephalidae gen. sp.); Filo Acanthocephala: juvenil de Quadrigyrus sp.; e Filo Nematoda: larvas de Brevimulticaecum sp., Contracaecum sp. Tipo1, Contracaecum sp. Tipo2, Hysterothylacium sp., Gnathostoma sp., Spiroxys sp.; juvenis e adultos de Freitascapillaria sp., Paracapillaria piscicola, Capillariidae gen. sp., Procamallanus (Spirocamallanus) hilarii, Procamallanus (S.) inopinatus, Procamallanus (S.) saofranciscencis, Travassosnema travassosi paranaensis, Cystidicoloides fischeri e Spinitectus rodolphiheringi. Proteocephalidae gen. sp., Contracaecum sp. Tipo1 e Travassosnema t. paranaensis foram compartilhadas entre todas as oito lagoas com altos índices parasitários. Proteocephalidae gen. sp., Brevimulticaecum sp., Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii, C. fischeri e S. rodolphiheringi são novos registros para A. lacustris. Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii e Travassosnema t. paranaensis têm sua distribuição geográfica estendida para a bacia do rio São Francisco.

Abstract The endoparasitic fauna of Acestrorhynchus lacustris from eight marginal lagoons of the upper and middle São Francisco river basin, Brazil, is recorded here for the first time. For this, a total of 106 specimens of A. lacustris were collected. Eighteen helminth species were found. The taxa recorded were phylum Platyhelminthes: one metacercaria of Clinostomum sp. (Trematoda: Clinostomidae) and plerocercoid larvae of unidentified species (Eucestoda: Proteocephalidae gen. sp.); phylum Acanthocephala: juvenile of Quadrigyrus sp.; and phylum Nematoda: larvae of Brevimulticaecum sp., Contracaecum sp. Type1, Contracaecum sp. Type2, Hysterothylacium sp., Gnathostoma sp., Spiroxys sp., juvenile and adult specimens of Freitascapillaria sp., Paracapillaria piscicola, Capillariidae gen. sp., Procamallanus (Spirocamallanus) hilarii, Procamallanus (S.) inopinatus, Procamallanus (S.) saofranciscencis, Travassosnema travassosi paranaensis, Cystidicoloides fischeri and Spinitectus rodolphiheringi. Proteocephalidae gen. sp., Contracaecum sp. Type1 and Travassosnema t. paranaensis were present in all eight lagoons with high parasitic indexes. Proteocephalidae gen. sp., Brevimulticaecum sp., Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii, C. fischeri and S. rodolphiheringi are new records for A. lacustris. The known geographical distribution of Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii and Travassosnema t. paranaensis has now been extended to the São Francisco river basin.

A fauna parasitária de mandis, Pimelodus pohli da bacia do rio São Francisco é apresentada. Um total de 45 mandis do alto rio São Francisco (45°15′44″W 18°13′25″S), foram examinados entre julho de 2009 e setembro de 2011. Quarenta e três mandis (95,5%) estavam infectados por pelo menos uma espécie de parasito tendo sido encontrados 885 parasitos de 17 espécies: Monogenea (Demidospermus uncusvalidus, Pavanelliella pavanellii, and Scleroductus sp.); Eucestoda (plerocercóides de Proteocephalidea); Digenea (metacercárias de Austrodiplostomum compactum, adultos de Auriculostoma platense e Kalipharynx sp. e juvenil de Prosthenhystera obesa); Nematoda (larvas de Contracaecum sp., Hysterothylacium sp., Procamallanus pimelodus, Procamallanus sp., larvas não identificadas de Cucullanidae e adultos de Cucullanus caballeroi, Philometra sp. e Procamallanus freitasi); e Acanthocephala (adultos de Neoechinorhynchus pimelodi). Procamallanus freitasi e Scleroductus sp. foram os táxons com prevalência mais elevada. Demidospermus uncusvalidus, P. freitasi e Scleroductus sp. foram as espécies dominantes. O sexo dos hospedeiros não influenciou os índices parasitários, mas houve alguma influência do comprimento total sobre eles. Os parasitos, com exceção de P. obesa, são registrados pela primeira vez em P. pohli, bem como a ocorrência de Kalipharynx sp. e C. caballeroi em hospedeiros pimelodídeos do rio São Francisco e da América do Sul.

The parasite fauna of catfish, Pimelodus pohli, from the São Francisco River Basin is presented. A total of 45 catfish from the upper São Francisco River (45°15′44″W 18°13′25″S), were examined from July 2009 to September 2011. Forty-three catfish (95.5%) were infected by at least one parasite species, with 885 parasite specimens being found, distributed across 17 species: Monogenea (Demidospermus uncusvalidus, Pavanelliella pavanellii, and Scleroductus sp.); Eucestoda (plerocercoids of Proteocephalidea); Digenea (metacercariae of Austrodiplostomum compactum, adults of Auriculostoma platense and Kalipharynx sp., and juvenile of Prosthenhystera obesa); Nematoda (larvae of Contracaecum sp., Hysterothylacium sp., Procamallanus pimelodus, Procamallanus sp., and unidentified of Cucullanidae, and adults of Cucullanus caballeroi, Philometra sp., and Procamallanus freitasi); and Acanthocephala (adults of Neoechinorhynchus pimelodi). Procamallanus freitasi and Scleroductus sp. were the taxa with the highest prevalence. Demidospermus uncusvalidus, P. freitasi, and Scleroductus sp. were the dominant species. The host's sex did not influence parasitic indexes; however, the total length of the catfish did appear to have some influence. The parasites, with except for P. obesa, were registered for the first time in P. pohli, as well as the occurrence of Kalipharynx sp. and C. caballeroi among pimelodid hosts from São Francisco River and South America.

Cento e doze espécimes de Cichla kelberi foram coletados no Reservatório de Três Marias, Alto São Francisco, Três Marias, MG, entre 2004 e 2005. Foram coletadas doze espécies de parasitos matazoários, sendo duas espécies de ectoparasitos: os monogenéticos Gussevia sp. e os copépodos Ergasilus sp.; e dez espécies de endoparasitos, sendo quatro espécies de endoparasitos adultos: os cestoides Proteocephalus macrophallus e P. microscopicus e os nematoides: Capillostrongyloides sentinosa e Rhabdochona acuminata, além de seis espécies de endoparasitos larvais: metacercárias de Austrodiplostomum compactum e os nematoides: Hysterothylacium sp., Contracaecum sp. Tipo 1, Procamallanus (Spirocamallanus) inopinatus, Spiroxys sp. e Goezia sp.. As associações positivas significativas observadas para os endoparasitos adultos P. macrophallus e P. microscopicus com correlação positiva entre suas abundâncias podem indicar que essas espécies tenham os mesmos requerimentos ecológicos; e para as espécies de endoparasitos larvais Hysterothylacium sp. e A. compactum, com correlações positivas entre suas prevalências podem indicar que houve oportunismo para ambas as espécies. Ergasilus sp., C. sentinosa, R. acuminata e Hysterothylacium sp. são registrados pela primeira vez em C. kelberi, ampliando assim a listagem de hospedeiros. Portanto, o Reservatório de Três Marias constitui nova localidade para ambas as espécies de proteocefalídeos e para C. sentinosa, ampliando assim a distribuição geográfica.

A total of 112 specimens of yellow peacock bass, Cichla kelberi, were collected in the Três Marias Reservoir, upper São Francisco River, State of Minas Gerais, between 2004 and 2005. Twelve species of parasites were collected: two species of ectoparasites (the monogenetic Gussevia sp. and the copepod Ergasilus sp.); and ten species of endoparasites, including four species of adult endoparasites: the cestodes Proteocephalus macrophallus and P. microscopicus, and the nematodes: Capillostrongyloides sentinosa and Rhabdochona acuminata, and six species of larval endoparasites: the metacercariae of Austrodiplostomum compactum and the nematodes: Hysterothylacium sp., Contracaecum sp. Type 1, Procamallanus (Spirocamallanus) inopinatus, Spiroxys sp., and Goezia sp.. A significant positive correlation in the abundance of the two adult endoparasites species, P. macrophallus and P. microscopicus, may indicate that such associated species had the same ecological requirements. The positive correlations between the prevalence of the larval endoparasites, Hysterothylacium sp. and A. compactum, may indicate that there was opportunism for the two generalists species. Ergasilus sp., C. sentinosa, R. acuminata and Hysterothylacium sp. were recorded for the first time in C. kelberi, and this increased their list of known hosts. In addition, both proteocephalid species and C. sentinosa can extend their known biogeographical distribution to the Três Marias Reservoir.

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.

Ergasilus chelangulatus sp. nov. é descrita do peixe de água doce, Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) do alto rio São Francisco, Minas Gerais, Brasil. A nova espécie está baseada em espécimes fêmeas e o macho é desconhecido. Esta espécie tem uma seta serrilhada no primeiro exopodito e tem o primeiro endopodito bi-segmentado, como a maioria das espécies amazônicas deste gênero. O corpo é alongado e projetado anteriormente. As antenas são alongadas com sensila proeminente no segundo e no terceiro segmentos. Ergasilus chelangulatus sp. nov. é distinta de todas as outras espécies conhecidas de Ergasilus por ter o quarto segmento antenal (garra) dobrado em ângulo quase reto.

Ergasilus chelangulatus sp. nov. is described from the freshwater fish, Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) of the upper São Francisco River, Minas Gerais State, Brazil. The new species is based on female specimens and the male is unknown. This species has a serrate seta on exopod one and a two-segmented first endopod, as do most Amazonian species of this genus. The body is elongate and produced anteriorly. The antennae are elongate and have prominent sensilla on segments two and three. Ergasilus chelangulatus sp. nov. can be distinguished from all known species of Ergasilus by the fourth antennal segment (claw) which is bent at nearly a right angle.

Ergasilus salmini sp. nov. um parasito das brânquias do "dourado", Salminus franciscanus Lima & Britski, 2007, do alto rio São Francisco, Minas Gerais, Brasil, é descrita baseada em espécimes fêmeas. A nova espécie tem uma seta curva, serrilhada, no primeiro exopodito como a maioria das espécies conhecidas deste gênero. A maioria dos ergasilídeos tem a cabeça e os dois primeiros segmentos torácicos completamente fusionados formando o cefalotórax. Na nova espécie, a cabeça é incompletamente fusionada, o primeiro segmento torácico é fusionado, mas o segundo segmento torácico é livre. Ergasilus hydrolycus Thatcher, Boeger & Robertson, 1984, também possui o segundo segmento torácico livre mas nessa espécie a cabeça é completamente fusionada e o terceiro segmento abdominal é o mais comprido. Na nova espécie, o terceiro segmento é o mais curto dos três. A nova espécie também é menor medindo 691 x 207 ìm comparado com 784 x 278 ìm em E. hydrolycus. Essa espécie tem o quarto endopodito bi-segmentado enquanto na nova espécie essa estrutura é tri-segmentada. Adicionalmente, a nova espécie é de um hospedeiro diferente e de um sistema hídrico distinto.

Ergasilus salmini sp. nov. a branchial parasite of the "dourado", Salminus franciscanus Lima & Britski, 2007, from the upper São Francisco river, Minas Gerais State, Brazil, is described based on female specimens. The new species has a serrate, curved seta on the first exopod as do most of the known South American species of the genus. Other than that, it does not closely resemble any known species of this genus. Many of the known ergasilids have head, and first two thoracic segments completely fused to form a cephalothorax. In the new species, the head is incompletely fused, the first thoracic segment is fused, but thoracic segment two is free. Ergasilus hydrolycus Thatcher, Boeger & Robertson, 1984, also has a free second thoracic segment but in that species the head is completely fused and the third abdominal segment is the longest. In the new species, the third segment is the shortest of the three. Also, the new species is smaller averaging 691 x 207 µ m compared to 784 x 278 µ m for E. hydrolycus. The latter species has a two-segmented fourth endopod whereas in the new species this structure is three-segmented. In addition, the new species is from a different host and a separate river system.

Specimens of monogeneans parasites found in the nasal cavities of Pimelodus maculatus from the São Francisco and Paraná rivers were identified as Pavanelliella pavanellii. Prevalence, mean intensity and mean abundance this species are presented. An ecological analysis of the results related to the drought periods and full of the river Paraná evidences that P. pavanellii is more abundant in the rainy station, whose temperature is higher. Pavanelliella pavanellii from P. maculatus is for the first time registered to São Francisco river, southeast Brazil.

Espécimes de monogenóideos parasitos das cavidades nasais de Pimelodus maculatus dos rios São Francisco e Paraná foram encontrados e identificados como Pavanelliella pavanellii. Prevalência, intensidade média e abundância média de P. pavanellii em P. maculatus são apresentadas para os dois sistemas hídricos. Resultados da análise ecológica relacionados à períodos de seca e cheia do rio Paraná evidenciaram elevação da abundância média de P. pavanelli no período de cheia, no qual a temperatura é mais alta. Pavanelliella pavanellii é o primeiro registro de monogenóideos das cavidades nasais de P. maculatus e é pela primei-ra vez encontrada no rio São Francisco, Brasil.

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli, 1998, in Pimelodus maculatus Lacépède, 1803 collected in the São Francisco river during periods of drought (July 1995 and 1996) and floodings (January 1996 and 1997) of this river basin are provided. In tropical regions where the amount of rainfall alters the hydrological regimen of limnological systems water temperature has not had an important role in infections of N. pimelodi in P. maculatus. Prevalence was somewhat higher during drought periods. Intensity of infection varied slightly between collecting periods. Mature male and female acanthocephalans were present in all periods. Females were predominant. Mature females were present in higher numbers during flooding periods with a corresponding decrease in juvenile acanthocephalans. Recruitment and constant losses of N. pimelodi seem to be controlled by transmission mechanisms independently of density. Mechanisms may consist of infected prey availability (potential intermediate hosts) and changes of preferred alimentary items in the diets of juvenile and mature P. maculatus.