Pathological alterations and autoecology of Didymocylindrus simplex in Katsuwonus pelamis (Linnaeus, 1758) in the Southwestern Atlantic Ocean off of South America are presented. This is the first record of the species in the region; the specimens are described. The pathologic changes observed most often were infiltration of lymphocytes and slight fibrosis of the connective tissue surrounding the parasite. The typical aggregated distribution pattern was observed for Didymocylindrus simplex Ishii, 1935. Statistical analysis demonstrated no correlation between the abundance and prevalence of parasites with the total length of the host. The sex of the host does not influence the prevalence and intensity of infection.

Four species of Scombridae from the coast of Rio de Janeiro, southwest Atlantic Ocean were found to be parasitized with species of Didymozoidae (Digenea): Thunnus atlanticus (Lesson) a new host record for Nephrodidymotrema ahi Yamaguti, 1970, Didymocystis neothunni (Yamaguti, 1970), and Didymozoon longicolle (Yamaguti, 1970); Thunnus obesus (Lowe) parasitized by Didymozoon longicolle and reported as a new host for Nephrodidymotrema ahi; Thunnus albacares (Bonaterre) parasitized by Nephrodidymotrema ahi, and Katsuwonus pelamis (Linnaeus) by Didymozoon longicolle. Measurements, figures, and parameters of infection are presented.

Cuatro especies de Scombridae de la costa de Río de Janeiro, suroeste del océano Atlántico, se reportan parasitados con diferentes especies de Didymozoidae (Digenea): Thunnus atlanticus (Lesson) un registro de nuevo huésped para Nephrodidymotrema ahi Yamaguti, 1970, Didymocystis neothunni (Yamaguti, 1970) y para Didymozoon longicolle (Yamaguti, 1970); Thunnus obesus (Lowe) parasitado por Didymozoon longicolle, se indica como nuevo huésped para Nephrodidymotrema ahi; Thunnus albacares (Bonaterre) parasitados por Nephrodidymotrema ahi y Katsuwonus pelamis (Linnaeus) por Didymozoon longicolle. Se presentan las mediciones, las figuras y los parámetros de la infección.

Philometra katsuwoni Petter & Baudin-Laurencin 1986, nematóide parasito do ovário de Katsuwonus pelamis (Linneaus 1758), originalmente descrito no Golfo da Guiné, é referido pela primeira vez na zona costeira do Estado do Rio de Janeiro, Brasil. Comparados com a descrição original, os machos do material brasileiro são um pouco maiores e possuem o espículo direito e o gubernáculo mais longos. A fêmea subgrávida é descrita pela primeira vez. Ela se caracteriza pela região anterior do esôfago inflada e pela presença de dois lobos caudais distintos.

The nematode Philometra katsuwoni Petter & Baudin-Laurencin, 1986, a gonad-infecting parasite of Katsuwonus pelamis (Linneaus 1758), originally described from the Gulf of Guinea, is reported for the first time from the coastal zone of Rio de Janeiro State, Brazil. As compared with the original description, the males of the Brazilian material are generally somewhat larger and their right spicule and the gubernaculum are longer. The subgravid female is described for the first time. It is characterized by the anterior inflation of the esophagus and by the presence of two distinct caudal lobes.

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.

Didymocystis lamotheargumedoi n. sp. is described from the operculum and palate of Thunnus atlanticus (Lesson, 1831), palate of Thunnus albacares (Bonnaterre, 1788), and the operculum of Katsuwonus pelamis (Linnaeus, 1758) caught on the coast of Rio de Janeiro, Brazil. The new species is most similar to D. alalongae (Yamaguti, 1938), D. exiguus (Yamaguti, 1970), and D. oesophagicola (Yamaguti, 1970), based on the vitelline and ovarian branches lacking ramifications. It variously differs from these 3 species in the number of ovarian and vitelline branches, the length of the vitelline branches, egg size, body size and site within the host. Immature forms associated with adults are also described.

Didymocystis lamotheargumedoi n. sp. se describe como parásito del opérculo y del paladar de Thunnus atlanticus (Lesson, 1831), del paladar de Thunnus albacares (Bonnaterre, 1788) y del opérculo de Katsuwonus pelamis (Linnaeus, 1758) capturados en la costa de Rio de Janeiro, Brasil. La especie nueva es semejante a D. alalongae (Yamaguti, 1938), D. exiguus (Yamaguti, 1970) y D. oesophagicola (Yamaguti, 1970), por la ausencia de ramificaciones en las vitelógenas y en los ovarios. Estas 3 especies difieren en el número de ramificaciones de las vitelógenas y ovarios, en la longitud de ramificaciones de las vitelógenas, tamaño del cuerpo y sitio dentro del hospedador. Se describen también las formas inmaduras asociadas con sus respectivas formas adultas.

Two species of Didymozoidae, Didymosulcus palati (Yamaguti 1970) and Didymosulcus philobranchiarca (Yamaguti 1970) were reported for the first time in South America, Atlantic Ocean, parasitizing three different tuna species from the coast of Rio de Janeiro, Brazil: Thunnus atlanticus (Lesson), Thunnus albacares (Bonnaterre) and Thunnus obesus (Lowe). Pairs of D. philobranchiarca were found on gill arches of T. albacares and T. obesus, in longitudinal rows of yellow cysts located inside grooves in the hard denticle palate (new site) of the three hosts species studied, and as disperse groups of cysts in the operculum (new site) and gill arches of T. atlanticus (new host record). D. palati occurred as disperse groups of encysted worm pairs in the gill arches of T. albacares and T. obesus and in gill arches and operculum of T. atlanticus (new host record). The pathological alterations induced by D. philobranchiarca in the palate of T. atlanticus are described for the first time. Original measurements and figures are presented.

Com o objetivo de avaliar a ação da lovastatina na postura do Schistosoma mansoni foram usados camundongos infectados com 100 ±10 cercárias da cepa LE. Trinta dias após a infecção, os animais foram tratados com 100, 200 e 400mg/kg de lovastatina, via oral, durante cinco dias consecutivos e sacrificados 7,15,30 ou 60 dias após o tratamento. Foram analisados: distribuição de vermes no mesentério e fígado, mortalidade de vermes no fígado, alteração do oograma, contagem de ovos no jejuno e fígado, presença de ovos intra-uterino e morfologia dos vermes dos grupos tratados e controle (animais infectados e não tratados). Diferenças estatisticamente significativas foram encontradas, na dose de 400mg/kg, entre grupos tratados e controles quando se considerou a presença de ovos no útero, a alteração do oograma, ovos nos diferentes estágios de desenvolvimento no jejuno e fígado e no comprimento do corpo dos vermes machos e fêmeas. O estudo morfológico dos vermes mostrou alterações degenerativas sendo as principais no aparelho reprodutor, com redução e alteração dos folículos vitelínicos e do ovário das fêmeas e modificações nos testículos dos machos. Os resultados apresentados levam à conclusão que a droga em estudo reduz, consideravelmente, a oviposição das fêmeas do S. mansoni, aumenta o tamanho dos vermes, provoca alterações no sistema reprodutivo de machos e fêmeas e pode ocasionar morte de parte significativa da população de vermes na dose de 400mg/kg.

Aimed to evaluate the lovastatin action on Schistosoma mansoni oviposition, infected mice with 100 ± 10 cercariae of the LE strain were used. Thirty days after infection the animals were treated with 100, 200 and 400mg/kg of lovastatin, per os, during five consecutive days and then sacrificed 7, 15, 30 or 60 days after treatment. We analyzed: distribution of worms in mesenteries and liver; mortality of worms in the liver; alteration of the oogram; eggs counting in the jejunum and liver; presence of intrauterine eggs and morphology of the worms from the treated and control groups (infected and not treated animals). Significant statistical differences were found between treated and control groups when the presence of intrauterine eggs was considered and also, alteration on the oogram, eggs at different stages of development in jejunum, liver and in the body length of males and females. The morphological study of the worms showed that the degenerative modifications occurred, mainly in the reproductive system, with reduction and alteration of the viteline follicles and the ovary of the females. Also modifications in the males testicles were observed. The results suggest that the drug under study reduces, considerably, the female S. mansoni, oviposition increases the worms' size, leads to alteration in the reproductive system of males and females. It also may induce death of a significant part of the worm populations at the dose of 400mg/kg.

Camundongos infectados experimentalmente com Schistosoma mansoni foram tratados, em dose oral única, com artesunato (LACTAB®), 300 ou 500mg/kg ou durante cinco dias consecutivos. Os animais foram sacrificados 7, 30, 60 ou 90 dias após o tratamento. Diferenças estatisticamente significativas foram encontradas na distribuição e mortalidade dos vermes e na alteração do oograma nos grupos tratados quando comparados ao controle, em todos os esquemas testados quando os animais foram sacrificados 30 dias após o tratamento. A análise morfológica dos vermes mostrou alterações no aparelho reprodutor feminino com diminuição do volume ovariano, rarefação dos folículos vitelínicos, alterações estas mais acentuadas nas dosagens mais altas, justificando o encontro na alteração do oograma que chegou a 100%. Entretanto, quando os animais foram sacrificados 60 ou 90 dias após o tratamento, as diferenças e alterações foram menores, mostrando que os vermes sobreviventes se recuperaram e reiniciaram a postura.

Mice experimentally infected with Schistosoma mansoni were treated orally with artesunate (Lactab®) in a single dose of 300 or 500mg/kg or over a period of five consecutive days. The animals were sacrificed 7, 30, 60 or 90 days after treatment. Statistically significant differences were found in the distribution and mortality of the worms and in the alterations of the oogram in the treated group when compared to control in all of the tested schemes when the animals were sacrificed 30 days after treatment. Morphological analysis of female worms showed a reduction of ovarian volume and rarefaction of the vitelline follicles. These modifications were more marked after treatment with the higher dose, explaining the alteration of the oogram which reached 100%. However, when the animals were sacrificed 60 or 90 days after treatment, the differences and alterations were smaller, showing that the surviving worms recovered and restarted oviposition.

An electron microscopic study of the vitelline follicles of Metamicrocotyla macracantha (Alexander, 1954) Koratha,1955 showed that they are composed of cells in different stages of development. The immature cells have a large nucleus, nucleolus, cytoplasm with free ribosomes and few mitochondria. The developing vitelline cells present granules which are small in the early stages, increasing with maturity. The mature cells have an extensive granular endoplasmic reticulum and droplets of shell-protein; with maturation, clusters of shell protein and yolk bodies are formed and released in the ciliated vitelline ducts. Vitelline development is continuous and all of the cellular stages involved can be found in each follicle.

Prosthenhystera obesa (Diesing,1850) Travassos, 1922 from the gall bladder of Astyanax bimaculatus, Caranx gibbosus, Galeocharax humeralis, Leporinus copelandii, Pimelodus fur, Pseudopimelodus roosevelti, Salminus brevidens, Salminus maxillosus and from the new hosts, Cynopotamus amazonum and Triurobrycon lundii is redescribed, demonstrating a large morphological variation, mainly in body and testes size and shape. New hosts harbouring immature specimens of P. obesa are presented: Brycon sp., Leporellus vittatus, Pachyurus squamipinnis, Pimelodus clarias, Pseudoplatystoma corruscans and Salminus hilarii. Scanning electron microscopy micrographies, original figures and measurements of adult and immature specimens from different Brazilian hosts and localities are presented

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.

Ultrastructural aspects of spermatogenesis, spermiogenesis and of the mature spermatozoon of a microcotylid monogenean Metamicrocotyla macracantha parasite from Mugil liza, are described. The irregularly-shaped spermatogonia divides by successive mitoses, forming the primary spermatocytes, identified by the presence of synaptonemal complexes in their nuclei. The spermatids formed by meiotic cell divisions of the secondary spermatocytes, differentiate into a mature spermatozoon. Cross sections of the head and the middle region of mature spermatozoa show the nucleus with strong condensed chromatin, the mitochondria with short cristae, peripheral microtubules and two axonemes with a 9+1 pattern, confirming the characteristics of this genus.

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.