ABSTRACT 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.

Abstract The Scombridae fishes are of great commercial importance in Brazil, but infections caused by helminth parasites can reduce its commercial value. Thunnus obesus from the coastal zone of Rio de Janeiro was examined for helminth parasites. Three species of Didymozoidae were found: Didymocystis alalongae Yamaguti, 1938 in gill raker and operculum, Didymocystis lamotheargumedoi Kohn & Justo, 2008 associated with 3 immature forms in the operculum and Platocystis vivipara (Yamaguti, 1970) Pozdnyakov, 1987 in the skin of dorsal region. T. obesus represent new host record for Didymocystis alalongue and for D. lamotheargumedoi and Platocystis vivipara is reported for the first time in the Southwest Atlantic Ocean.

Resumen Los peces Scombridae son de gran importancia comercial en Brasil, pero las infecciones causadas por helmintos pueden reducir su valor comercial. Thunnus obesus de la zona costera de Río de Janeiro, fue examinado en busca de helmintos. Se encontraron 3 especies de Didymozoidae: Didymocystis alalongue Yamaguti, 1938 en branquiespinas y opérculo, Didymocystis lamotheargumedoi Kohn & Justo, 2008 asociado con 3 formas inmaduras en el opérculo y Platocystis vivipara (Yamaguti, 1970) Pozdnyakov, 1987 en la piel de la región dorsal. T. obesus representa un registro nuevo de hospedero para Didymocystis alalongue y para D. lamotheargumedoi y Platocystis vivipara, se registra por primera vez en el suroeste del océano Atlántico.

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 total dos hospedeiros, e nos viveiros com o comprimento total, peso e fator de condição dos hospedeiros. Nos viveiros, a infracomunidade de endoparasitos apresentou os maiores índices de riqueza, dominância, diversidade e equitabilidade. Nos açudes, os ectoparasitos apresentaram os maiores índices. Este foi o primeiro registro de índices parasitários de L. macrocephalus em sistemas de cultivo na Amazônia.

ABSTRACT 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.

During a survey of the helminth parasites of Ctenosciaena gracilicirrhus from the Atlantic Ocean, off Angra dos Reis, Rio de Janeiro State, Brazil, 10 species of metazoan parasites were collected: 1 species of Monogenea (Choricotyle rohdei); 3 species of Nematoda (Hysterothylacium sp. third stage larvae, Raphidascaris sp. third stage larvae, and Procamallanus (Spirocamallanus) pereirai third and fourth stages larvae and adults); 6 species of Digenea (Opecoeloides pedicathedrae, Opecoeloides melanopteri, Diplomonorchis leiostomi, Aponurus laguncula, Parahemiurus merus and Manteriella sp.). Choricotyle rohdei and Hysterothylacium sp. had the highest prevalence, mean intensity and abundance and an aggregated pattern of distribution was observed in both species. A positive correlation between the standard length of hosts and the parasitic abundance of Hysterothylacium sp. and C. rohdei was observed. The prevalence of C. rohdei was positively correlated with standard length of the host, while in Hysterothylacium sp. there was no correlation. Ctenosciaena gracilicirrhus represents a new host record to all species of Nematoda and Digenea presented herein. The genus Manteriella is reported for the first time in South America.

Durante un estudio de los helmintos de Ctenosciaena gracilicirrhus de la zona costera de Angra dos Reis, Rio de Janeiro, Brasil, 10 especies de parásitos metazoos fueron recolectados: 1 especie de Monogenea (Choricotyle rohdei); 6 de Digenea (Opecoeloides pedicathedrae, Opecoeloides melanopteri, Diplomonorchis leiostomi, Aponurus laguncula, Parahemiurus merus y Manteriella sp.); 3 nemátodos (Hysterothylacium sp. y Raphidascaris sp., ambas larvas de tercer estadio y Procamallanus (Spirocamallanus) pereira, larvas de tercer y cuarto estadios y adultos). Choricotyle rohdei y Hysterothylacium sp. presentaron la mayor prevalencia, intensidad media y abundancia, así como un patrón agregado de distribución. Se observó una correlación positiva entre la longitud estándar de los hospederos y la abundancia parasitaria de Hysterothylacium sp. y C. rohdei. La prevalencia de Choricotyle rohdei se relaciona positivamente con la longitud estándar del huésped, mientras que en Hysterothylacium sp., no hubo correlación. Ctenosciaena gracilicirrhus representa un nuevo registro de huésped para todas las especies de Digenea y Nematoda registrados en este trabajo. El género Manteriella se registra por primera vez en América del Sur.

Cinquenta e quatro espécimens de peixes marinhos pertencentes a sete espécies coletados do litoral do estado do Rio de Janeiro, Brasil foram examinados para helmintos, os resultados referentes a Monogenea e Digenea são apresentados. Os monogenéticos Metamicrocotyla macracantha, Microcotyle pomatomi e Gotocotyla acanthura são apresentados em novos hospedeiros. Os digenéticos Parahemiurus merus, Lecithochirium microstomum, Gonocercella pacifica, Aponurus laguncula, Gonocerca trematomi e Lampritrema miescheri são registrados em novos hospedeiros, as duas últimas espécies são também registradas pela primeira vez no Brasil.

Fifty four specimens of marine fish belonging to seven species collected from the coast of the State of Rio de Janeiro, Brazil were examined for helminths, and results relating to Monogenea and Digenea are presented. The monogeneans Metamicrocotyla macracantha, Microcotyle pomatomi and Gotocotyla acanthura are reported in new hosts. The digeneans Parahemiurus merus, Lecithochirium microstomum, Gonocercella pacifica, Aponurus laguncula, Gonocerca trematomi and Lampritrema miescheri are reported in new hosts, and the latter two species are also reported for the first time in Brazil.

Oito espécies de Demidospermus (Dactylogyridae, Monogenea) foram coletadas de peixes Siluriformes do reservatório da Usina Hidrelétrica de Itaipú, Paraná, Brasil. Quatro dessas são registradas pela primeira vez no Brasil, aumentando sua distribuição geográfica: Demidospermus armostus, Demidospermus anus, Demidospermus bidiverticulatum e Demidospermus valenciennesi. Demidospermus labrosi é considerada sinônima de Demidospermus cornicinus e Demidospermus mandi sinônima de Demidospermus leptosynophallus e registradas em dois novos hospedeiros. Foram também coletados exemplates de Demidospermus paravalenciennesi e Demidospermus uncusvalidus.

Eight known species of Demidospermus (Dactylogyridae, Monogenea) were collected from siluriform fishes from reservoir of the Itaipu Hydroelectric Power Station, Paraná, Brazil. Four of them are recorded for the first time in Brazil, enlarging their geographical distribution: Demidospermus armostus, Demidospermus anus, Demidospermus bidiverticulatum and Demidospermus valenciennesi. Demidospermus labrosi is synonymized with Demidospermus cornicinus and Demidospermus mandi with Demidospermus leptosynophallus and reported from two new hosts. Demidospermus paravalenciennesi and Demidospermus uncusvalidus were also collected.

During parasitological studies on different localities along the Paraná River, State of Paraná, Brazil, a new species of Notozothecium (Dactylogyridae) was found parasitizing gills of the freshwater fish Rhaphiodon vulpinus (Cynodontidae). The new species is allocated to Notozothecium based on the presence of a ventral bar with anteromedial projection, a copulatory complex comprising a coiled male copulatory organ (MCO) with a counterclockwise incomplete ring and accessory piece with proximal articulation process and a dextrodorsal vagina, looping the right intestinal caecum. Notozothecium lamotheargumedoi n. sp. is similar to Notozothecium janauachensis, by the absence of terminal flabellate plate on the accessory piece, but differs from it in the shape of the bars, the copulatory complex and the difference of the size-ratio between ventral and dorsal anchors, which in N. janauachensis is larger.

Durante varios estudios en diversas localidades del río Paraná, estado de Paraná, Brasil, una especie nueva de Notozothecium fue encontrada en los filamentos branquiales de Rhaphiodon vulpinus, peces de agua dulce pertenecientes a Cynodontidae. La especie nueva se asigna a Notozothecium con base en la barra ventral, que está provista de una proyección anteromedial, un complejo copulador que abarca un órgano copulador en espiral a la izquierda, una pieza accessoria con proceso proximal y la vagina dextrodorsal, dando la vuelta en el ciego intestinal derecho. Notozothecium lamotheargumedoi n. sp. se asemeja a Notozothecium janauachensis por la ausencia de placa flabelada terminal en la pieza accesoria; no obstante, difieren por la forma de las barras, por el complejo copulador y por la relación entre las anclas ventrales y dorsales, que en N. janauachensis es mayor.

The tegument of the adult form of Prosorhynchoides arcuatus (Linton, 1900) (Trematoda, Bucephalidae) from the intestine of Pomatomus saltator (L.) from the Atlantic coast of the State of Rio de Janeiro, Brazil was studied by transmission electron microscopy. The tegument consists of two layers: an external, constituted by a syncytium, containing spines, unicilliated papillae, inclusion bodies and mitochondria and an internal, consisting of a muscular layer and mononucleated tegumental cells.

Prosorhynchoides arcuatus (Linton, 1900) from the intestine of Pomatomus saltator (L.) from the Atlantic coast of the State of Rio de Janeiro is studied by scanning electron microscopy, with detailed description of tegumental spines. Comments on the synonymy of this species with Bucephalopsis callicotyle Kohn, 1962 are made. The tegument of adult P. arcuatus presents scale like and serrated spines and uniciliated sensory papillae, distributed over the body surface and is compared with other digenetic trematodes.