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Members of the genus Kudoa Meglitsch, 1947 are known to infect the muscles of commercially important fishes worldwide, including those in the order Siluriformes. This paper describes the occurrence of a new species of Kudoa in the catfish Brachyplatystoma rousseauxii based on morphological study and molecular analysis of the ribosomal RNA gene (SSU rDNA).Fifteen specimens of Brachyplatystoma rousseauxii were purchased from fishing zones near Mosqueiro Island, Belém, Pará, Brazil. After necropsy, tissue samples and cysts were analyzed using a stereomicroscope, and fresh slides were viewed under a light microscope to confirm parasitic infection. The tissue fragments were removed and processed for molecular and histological analyses.Microscopic pseudocysts were found in the epaxial region of skeletal muscle fibers in 80% of the analyzed specimens. The myxospores were quadrangular with four shell valves (SV), pyriform polar capsules (PC), and internal symmetry. Phylogenetic analyses indicated that the new species formed a cluster with the species previously described in the Amazon, being close to two freshwater species.Morphological differences and molecular data of SSU rDNA support that Kudoa rousseauxii n. sp. is a new species that infects B. rousseauxii, a freshwater fish with intense migratory cycles that is widely captured and consumed in the Amazon.

The class Myxozoa consists of microscopic spores that typically present uniform morphological simplifications, containing one or two sporoplasms surrounded by valve cells. The present study analysed the morphological and phylogenetic characteristics of what proved to be a new species of Ceratomyxa found in the gallbladder of Mesonauta festivus Heckel, 1840 captured on the Piririm River in the municipality of Macapa, in Amapa state, Brazil. The fish were collected in gillnets, and were transported alive to Amapa State University in Macapa for the analysis of the organs. Crescent- or arch-shaped free spores were observed under light microscopy, containing two polar capsules and a suture line, which is typical of the morphology of the genus Ceratomyxa, contained within plasmodia that had snake-like movements. The gallbladder was conserved in 80% alcohol for the analysis of the 18S rDNA gene, and in Davidson solution for standardhistology. Ceratomyxa spores (n = 20) were observed in 11 of the 50 samplesanalysed, and thus had a prevalence of 22%, and had a mean length of 4.2 ± 0.5 µm, mean thickness of 22.75 ± 0.3 µm, and two polar capsules, 1.86 ± 0.3 µm long and 1.63 ± 0.1 µm thick. The phylogenetic analysis indicated that the new species forms a cluster with other freshwater Amazonian Ceratomyxa species, described previously. The new species represents the first description of a taxon of the genus Ceratomyxain fish from the Brazilian state of Amapa.

Nas regiões neotropicais, há estimativa de 9.100 espécies de peixes, e centenas de espécies novas são descritas anualmente, o qual a bacia amazônica abriga cerca de 2200 espécies de peixes corresponde a essa estimativa. Leporinus friderici é um peixe da ordem Characiformes conhecido popularmente como 'piau três pintas' ou 'aracú', trata-se de uma espécie abundante nas regiões neotropicais, que possui hábitos alimentares onívoros, se alimentando de material vegetal, detritos, frutos, sementes, camarão e pequenos peixes. É um peixe muito utilizado na alimentação pela qualidade de sua carne e é facilmente encontrado na região do Rio Matapí-AP. Foram realizadas coletas trimestrais durante setembro de 2015 a maio de 2016 e de agosto de 2017 a outubro de 2018, onde foram capturados 49 espécimes de L. friderici. A fauna de L. friderici foi bastante diversificada, sendo composta por macro e microparasitos, infectando brânquias, intestino, fígado, vesícula biliar, coração, nadadeira e baço do hospedeiro. Durante as análises foram encontrados quatro taxa, sendo eles: Nematoda, Platyhelminthes, Cnidaria (Myxozoa) e Ciliophora, e nove grupos de parasitos, Anisakidae gen. sp., Contracaecum sp., Dactylogyridae gen. sp., larvas de digenea (metacercária), Henneguya sp., Myxobolus sp., Ceratomyxa sp., Piscinoodinium pillulare, Ichthyophthirius multifiliis, Trichodina sp. e Chilodonella sp.. A ocorrência de micropasitos eucariotos foi a primeira registrada para L. friderici do estado do Amapá.

Objetivou-se nesse trabalho verificar a carga parasitária da espécie Satanoperca jurupari (Heckel,1840) e sua relação com a resposta bioquímica por meio da determinação dos teores de tióis totais (GSH) e dos produtos finais da lipoperoxidação, aspectos até então não estudados para a espécie e região. As coletas foram realizadas de outubro de 2017 à outubro de 2018, no rio Curiaú, zona rural da capital do Estado do Amapá. A análise de estresse oxidativo foi determinado após a homogenização do fígado de peixes da espécie Satanoperca jurupari, para determinar os produtos finais da peroxidação lipídicas (SRAT) e GSH. Para análise parasitológica, utilizou-se as técnicas de microscopia de luz (DIC e Histologia). Nos resultados obtidos do presente trabalho, há correlação negativa (-0,474) entre os teores de glutationa reduzida e SRAT, evidenciado níveis de estresse oxidativo moderados, com consumo de GSH e elevação dos teores de SRAT, porém não há ocorrência exacerbada de danos oxidativos às biomoléculas. Devido a carga parasitária é evidente o consumo de GSH de forma acentuada e a geração moderada de danos nos lipídeos de membrana causados pela infecção por parasitos. Foram identificados 3 gêneros do subfilo Myxoza: na vesícula biliar, Ceratomyxa e Ellipsomyxa, nas brânquias, Henneguya. Nas nadadeiras, tegumento, boca, brânquias, opérculo e olhos foi encontrado 1 representante do filo Microsporidia. Registrou-se pela primeira vez a ocorrência de microparasitas dos gêneros Ellipsomyxa e Ceratomyxa, e a segunda de Henneguya, assim como o primeiro registro de ocorrência de microsporídio para esta espécie. Com base em uma abordagem biológica integrada inferindo que a função de defesa antioxidante (GSH) e a oxidação dos lipídicos (SRAT) foram impactadas pela taxa de infecção, de forma sistêmica, sugerindo que funções hepáticas são alteradas. Estes resultados revelam a necessidade de maiores estudos referentes às características biológicas como detalhamento em microscopia eletrônica e biologia molecular para identificação e descrição a nível de espécie. O presente estudo forneceu também informações valiosas sobre efeitos de parasitas em uma espécie amazônica e sublinhou a importância da avaliação da associação dos marcadores de estresse oxidativo e a carga parasitária.

Fish are among the vertebrate groups most susceptible to parasitic infections due to environmental characteristics that can favor the development of parasites; also, position of the host in food web has been associated with the parasitism. The aim of this study was to investigate the ecology of parasites endohelminth in Metynnis lippincottianus from the Curiaú River, in eastern Amazon (Brazil), as well as to evaluate the parasite-host interactions. From 110 specimens of M. lippincottianus examined, 76.3% were infected by one or more parasite species, and a total of 146 parasites such as Procamallanus (Spirocamallanus) inopinatus (Nematoda), larvae of Contracaecum sp. (Nematoda) and Neoechinorhynchus pterodoridis (Acanthocephala) were collected in intestine. However, the dominance was of nematode species, and the parasites had uniform or random dispersion. The parasitic infracommunities showed low Shannon-Wiener diversity (0.2 ± 0.3), low evenness (0.2 ± 0.3) and low species richness of parasites (1.1 ± 0.8). The abundance of Contracaecum sp. presented a weak positive correlation with the weight of hosts, and relative condition factor was not affected by the parasitism. This first study about parasites of M. lippincottianus from Curiaí River basin is the first report of N. pterodoridis for this host.

Myxozoans of the family Myxobolidae are common parasites in fish. The diversity and ecology of the species of the genus Unicauda are poorly known, which hampers the understanding of the distribution and prevalence of this group of parasites. In the present study, cysts containing parasites whose morphology was consistent with the genus Unicauda were found in the circumorbital region of the ocular conjunctiva of the freshwater fish Moenkhausia grandisquamis Muller & Troschel, 1845 (Characiformes: Characidae) and Triportheus angulatus Spix & Agassiz, 1829 (Characiformes: Triportheidae). The spores have an oval body and long caudal appendage, with a mean total length of 65.2 ± 5.9 μm and width of 5.2 ± 0.7 μm, with two oval and symmetrical polar capsules of 4.9 ± 0.5 μm in length and 1.4 ± 0.2 μm in width, containing polar filaments with five or six coils. An integrated comparative analysis of the morphological characteristics of this parasite and partial sequences of the SSU rDNA gene supported the identification of a new species of histozoic parasite of the genus Unicauda found in fish from the Tocantins River basin, in the eastern Brazilian Amazon region. The new species was denominated by Unicauda tavaresii n. sp.

Myxozoans of the family Ceratomyxidae are common coelozoic parasites of marine, anadromous, and freshwater fish, and may also be found, less frequently, parasitizing the tissue of these hosts. The diversity and ecology of the freshwater species of the genus Ceratomyxa have been poorly investigated, leading to a knowledge gap that restricts the understanding of the distribution and prevalence of this group of parasites. In the present study, parasites were found inside vermiform plasmodia, characterised by oscillatory movements in the characiform species Hemiodus unimaculatus. The crescent-shaped and elongated spores, perpendicular to the suture line, have a mean length of 28.9 ± 2.7 μm and width of 2.6 ± 0.1 μm, with two symmetrical oval polar capsules, 1.9 ± 0.3 μm in length and 1.7 ± 0.2 μm in width, containing polar filaments with three or four coils, located near the central suture, with symmetrical lateral elongations 14.3 ± 1.1 μm in length and binucleate amoeboid sporoplasm. The integrated comparative analysis of the morphological characteristics and partial SSU rRNA sequences supported the identification of a new species of coelozoic Ceratomyxa, found in the gallbladder of H. unimaculatus, from the Tocantins basin, in the municipalities of Estreito and Imperatriz in eastern Brazilian Amazonia.The new species was denominated Ceratomyxa fonsecai n. sp.

This study describes aspects of infection caused by Myxozoa of the genus Henneguya sp. in gills of fish belonging to the species Metynnis hypsauchen. Two sampling were made in the Capim river, close to the Ribeira community, in the municipality of Ipixuna do Para, State of Para, Brazil, during the months of August 2018 and March 2019. The animals were captured and transported live to the Laboratorio de Pesquisa Carlos Azevedo, at the Universidade Federal Rural da Amazonia (UFRA), in Belem, Para, Brazil. The animals were examined, and after parasitism was confirmed, Differential Interference Contrast Microscopes were used, to evaluate the parasite spores. Ziehl–Neelsen stain techniques were used in histology. Necroscopic analyses of Metynnis hypsauchen specimens found parasites in 80% of the hosts (16/20), with whitish-colored cysts in the branchial filaments, containing mature spores of the genus Henneguya. The histopathological analysis indicated large areas with cystic lesions with associated ischemic necrosis. The descriptions from this study indicate that the parasite drastically compromises the host’s respiratory system. Additionally, it is worth noting that parasite fauna studies of fishes in the Capim river are still a vast topic for research; this is the first record of infection by Henneguya sp. in Metynnis hypsauchen, captured in the Capim river in Ipixuna do Para.

Federal Rural University of Amaz?nia. Paragominas, PA, Brazil. Federal Rural University of Amazonia. Carlos Azevedo Research Laboratory. Bel?m, PA, Brazil. Amap? State University. Laboratory of Morphophysiology and Animal Health. Macap?, AP, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Laborat?rio de Epidemiologia e Imunologia Aplicada ? Leishmaniose. Ananindeua, PA, Brasil. Federal University of Par?. Laboratory of Biomolecular Technology. Bel?m, PA, Brazil. Federal Rural University of Amazonia. Carlos Azevedo Research Laboratory. Bel?m, PA, Brazil. The class Myxozoa is a group of spore-producing eukaryote organisms that parasitize both freshwater and marine fish. The multivalvulide myxosporidian parasites of the genus Kudoa infect primarily the musculature of the fish host, some species are producing enzymes (proteases) capable of digesting muscle fibers. In the present study, 50 specimens of the freshwater catfish Hypophthalmus marginatus were collected from the Tocantins River in Par?, Brazil, and were analyzed. Overall, 68% of these specimens presented infections by Kudoa parasite in the esophageal musculature. The morphology of these parasite was examined under light microscopy and nucleotide sequences of the SSU rDNA gene were obtained for phylogenetic analyses. The species formed numerous whitish pseudocysts containing square spores with rounded extremities in the apical view, and four polar capsules of equal size. In the phylogenetic analyses, Kudoa amazonica n. sp. was characterized as a sister taxon of another freshwater species, Kudoa orbicularis. The combination of morphological, morphometric, and molecular data obtained in the present study provided a conclusive diagnosis of Kudoa amazonica n. sp., which is clearly distinct from all other Kudoa taxa described to date.

Calyptospora species are coccids that commonly cause liver infections in fish all around the world. This paper describes the morphology and histopathological characteristics of liver infection caused by Calyptospora sp. in black piranha Serrasalmus rhombeus, from the Capim River, in the municipality of Ipixuna do Pará, state of Pará (Brazil). Specimens were collected, analyzed and necropsied and tissue fragments containing parasites were prepared for histology and scanning electron microscopy. Parasitism was detected in 33.0% of the analyzed specimens, which had spherical oocysts in the liver, with four pyriform sporocysts presenting sporozoites internally. A histological examination revealed oocysts positioned close to blood vessels, causing necrosis and degeneration of hepatic parenchyma, while the presence of mononuclear cell infiltrate and melanomacrophages indicated the onset of an inflammatory process. This is the first record of the genus Calyptospora in fish from the Capim River. Resumo Calyptosporídeos são coccídeos constantemente encontrados causando infecções hepáticas em peixes de todo o planeta. Este estudo descreve a morfologia e características histopatológicas da infecção hepática causada por Calyptospora sp. encontrados em Serrasalmus rhombeus, a piranha negra, oriunda do rio Capim, em Ipixuna do Pará, Brasil. Os animais foram coletados, analisados e necropsiados; fragmentos teciduais com a presença dos parasitos foram processados para histologia e microscopia eletrônica de varredura. O parasitismo ocorreu em 33,0% dos espécimes analisados, onde foram encontrados oocistos esféricos no fígado, com esporocistos piriformes, apresentando internamente esporozoítos. No exame histológico, os oocistos estavam dispostos próximos aos vasos sanguíneos, causando necrose e degeneração do parênquima hepático; a presença de infiltrado de células mononucleares e melanomacrófagos indicaram o início de um processo inflamatório. Este é o primeiro registro do gênero Calyptospora em peixes do rio Capim.

A total of 30 specimens of the Amazonian electric knifefish, Brachyhypopomus beebei Schultz, 1944 (Gymnotiformes: Hypopomidae), were collected from the Peixe-Boi River in the state of Pará, Brazil (1°06’59” S; 47°18’26” W). Fragments of the brain tissue were extracted for analysis via optical microscopy, and 18 specimens (60%) presented microparasites of the genus Myxobolus, with unequal capsules. The spores were 18.6 µm (17.7-19.8 µm) long and 8.6 µm (8.4-9.0 µm) wide; the largest polar capsule was 13.0 µm (12.4-13.4 µm) long and 5.6 µm (5.3-6.0 µm) wide, and the smallest capsule was 5.0 µm (4.5-5.3 µm) long and 2.5 µm (2.3-2.6 µm) wide. Infected brain fragments were extracted for histological processing and staining with hematoxylin-eosin and Ziehl-Neelsen. Some fragments were conserved in ethanol for molecular genetics analysis. A partial sequence of the 18S DNA gene was obtained from the spores, which did not correspond to any other sequences deposited in GenBank, although it did form a clade with other Myxobolus parasites of the nervous system. The morphological data, together with molecular phylogeny, supported the designation of a new species Myxobolus freitasi n. sp.

The present study describes Hoferellus jutubensis n. sp., a myxozoan parasite found in the urinary bladder of the driftwood catfish Ageneiosus inermis, captured on Jutuba Island in the state of Para, northern Brazil. A total of 30 A. inermis specimens were examined, of which 26 (86.7%) had myxospores and polysporic plasmodia of varying shapes and sizes dispersed in the lumen of the urinary bladder, either floating freely or attached to the epithelium. In the apical view, the myxospores of Hoferellus jutubensis n. sp. are rounded, 6.1 ± 0.2 (5.7–6.3) μm long and 5.5 ± 0.3 (5.2–6.0) μm wide, with two sub-spherical polar capsules, equal in size and shape, 2.5 ± 0.2 (2.3–2.7) μm long and 1.7 ± 0.2 (1.4–2.2) μm wide. The phylogenetic analysis of a partial sequence of the SSU rDNA gene, indicated that the new species is the sister taxon of Hoferellus azevedoi, with these two species forming a Brazilian lineage of Hoferellus. The comparison of the morphological and molecular data with those of the existing members of the genus confirmed the species status of Hoferellus jutubensis n. sp., which adds one further Hoferellus taxon to the known myxosporean diversity of the Amazon basin.

Fish are among the vertebrate groups most susceptible to parasitic infections due to environmental characteristics that can favor the development of parasites; also, position of the host in food web has been associated with the parasitism. The aim of this study was to investigate the ecology of parasites endohelminth in Metynnis lippincottianus from the Curiaú River, in eastern Amazon (Brazil), as well as to evaluate the parasite-host interactions. From 110 specimens of M. lippincottianus examined, 76.3% were infected by one or more parasite species, and a total of 146 parasites such as Procamallanus (Spirocamallanus) inopinatus (Nematoda), larvae of Contracaecum sp. (Nematoda) and Neoechinorhynchus pterodoridis (Acanthocephala) were collected in intestine. However, the dominance was of nematode species, and the parasites had uniform or random dispersion. The parasitic infracommunities showed low Shannon-Wiener diversity (0.2 ± 0.3), low evenness (0.2 ± 0.3) and low species richness of parasites (1.1 ± 0.8). The abundance of Contracaecum sp. presented a weak positive correlation with the weight of hosts, and relative condition factor was not affected by the parasitism. This first study about parasites of M. lippincottianus from Curiaí­­ River basin is the first report of N. pterodoridis for this host.

Coelozoic parasites of the family Myxidiidae were observed in fish of the order Characiformes captured in the middle Tocantins River, Maranhao, Brazil, within the transition between the Cerrado savanna biome and the eastern extreme of the Brazilian Amazon Forest. The analysis of the morphological characteristics of the parasites, complemented with a Bayesian phylogenetic analysis, supported the description of new specie Myxidium imperatrizensis n. sp., found parasitising the gallbladder of specimens of the fish Triportheus angulatus. The study is also only the second report of the occurrence of Myxidium parasites in fish of the family Triportheidae in Brazilian rivers. The results of the present study expand the known distribution of the genera Myxidium the basin of the Tocantins River, the largest hydrographic basin located entirely within Brazil, which encompasses parts of both the Cerrado and Amazon biomes.

The coccidians of the family Calyptosporidae are parasites of the tissue and organs of fish and aquatic invertebrates, in particular in the tropical region. In contrast with other apicomplexans of the suborder Eimeriorina, the diversity and ecology of the species of the genus Calyptospora have been poorly investigated, resulting in a lacuna that restricts the understanding of the distribution and prevalence of this group of eukaryote microparasites in the Amazon region. In the present study, the integrated comparative analysis of morphological characteristics, histological and structural traits, and the sequences of a fragment of the 18S rRNA gene, provides support for the identification of a new species of Calyptospora, found parasitizing the hepatic tissue of the piscivorous blue peacock bass, Cichla piquiti, captured in the reservoir of the Estreito hydroelectric dam on the middle Tocantins River in northern Brazil. This new species was named Calyptospora paranaidji n. sp.

A new species of myxozoan, Kudoa viseuensis n. sp. (Myxosporea: Multivalvulida), is described based on specimens extracted from the musculature of the Pacuma toadfish, Batrachoides surinamensis, collected in the municipality of Viseu, in the northern Brazilian state of Para. A total of 60 specimens of B. surinamensis were examined, of which 52 (86%) presented whitish pseudocysts containing numerous rounded spores (7.2±0.2 μm in length and 5.2±0.2 μm in width). These spores have four polar capsules of equal size, measuring 1.8±0.2 μm x 1.3±0.1 μm in the apical view, and 2.7±0.2 μm x 1.3±0.1 μm in the lateral view. A partial sequence (1400 bps) of the small subunit ribosomal RNA gene was obtained and deposited in GenBank (access number: MK256272). The comparison of the morphological and molecular data with those of other Kudoa species supported the description of a new species of mixosporean from the Amazon region, which is denominated here as Kudoa viseuensis n. sp.

Henneguya quelen n. sp. (Myxosporea) is described from the kidney of the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), from Marajo Island. In all, 40% of the 57 silver catfish collected from the Paracauari River in the municipality of Salvaterra presented cysts in the kidney. The cysts were whitish, spherical, and 0.45 mm in diameter. The histological analyses revealed tubular renal compression and cellular degeneration in the area adjacent to the xenomas. The spores are ellipsoid, with well-marked valves, caudal projection, and two elongated polar capsules of equal size. The mature spores measure approximately 15.6 μm in length, with the caudal appendage split posteriorly; 24.3 μm in length, for a total spore length of 40.0 μm; and a width of 4.1 μm. The polar capsules are pyriform, 5.5 μm long and 1.7 μm wide. A phylogenetic analysis based on Bayesian inference confirmed that the specimens represented a new species, which was denominated Henneguya quelen n. sp.

Kudoa ocellatus n. sp. was found in the musculature of Astronotus ocelattus (Agassiz, 1831) from the Arari River on Marajo Island in Para, Brazil. The new species forms pseudocysts in the epaxial and hypaxial musculature composed of various spores that are pseudoquadrate in the apical view. In the lateral view, the spores were triangular or pyramidal. In the lateral view, the spores were 46 ± 0.11 μm (4.5–4.8) in length and 6.6 ± 0.3 μm (6.2–7.2) in width, with four pyriform polar capsules of equal size that measured 2.0 ± 0.16 μm (1.8–2.2) in length and 1.5 ± 0.18 μm (1.3–1.8) in width. Based on the partial (1418 bps) sequence of the SSU rDNA gene, Kudoa ocellatus n. sp. was distinct from all the other Kudoa species deposited in GenBank. The phylogenetic Bayesian Inference and P distance placed the new species together with the other Kudoa species that parasitize freshwater Amazonian fish. The morphological evidence, together with the SSU rDNA gene sequence, supported the description of Kudoa ocellatus n. sp., a distinct new species of the genus, which parasitizes a freshwater Amazonian cichlid.

Thoracocharax stellatus (KNER, 1858), pertencente a famíliaGasteropelecidae, é representada por peixes de pequeno porte, com grande importância econômica, pois é uma das 725 espécies de peixes nativos permitidos para explotação com finalidade ornamental.Os peixes foramcapturados com auxílio de tarrafas em uma área adjacente do Rio Guamá, com o comprimento total médio de 4,2±0,8 cm e peso total médio de 0,9±0,3 g.Fragmentosde brânquias foram coletadose analisados a fresco em microscópio de luz, onde foram observados a presença de cistos repletos de esporos de Myxobolus sp. com capsulas polares desiguais. Este estudorelatacomo primeiro registro ascaracterísticasmorfológicas de Myxobolus sp.encontradoem T. stellatus, provenientesde um rio tropical, Amazônia.Palavras-chave: Água doce, peixe ornamental, microparasitos.

Hoferellus azevedoi n. sp. was found in the urinary bladder of Chaetobranchus flavescens Heckel, 1840 from the Arari River on Marajó Island in Pará, Brazil. This is the first record of a species of the genus Hoferellus in a host from the Brazilian Amazon region. The new species has disporous and polysporous plasmodia, which vary in size and shape, with some being found adhered to the epithelium of the urinary bladder, and others floating in the liquid. The mature spores are sub-spherical in the sutural view, with a number of peripheral projections around the whole surface of the spore. In the sutural view, the spores are 5.3 ± 0.2 (5.2-5.6) μm in length and 7.0 ± 0.7 (6.3-7.7) μm in width, with two piriform polar capsules of equal size, 2.5 ± 0.2 (2.3-2.8) μm long and 1.8 ± 0.2 (1.6-2.0) μm wide. Based on a partial (1312 bps) sequence of the SSU rDNA gene, Hoferellus azevedoi n. sp. was distinguished from all the other myxozoan species deposited in GenBank. Phylogenetically, based on Bayesian inference and p-distances, the new species was allocated to the "Freshwater Urinary-Bladder" clade, together with other myxozoan parasites of the excretory system. Based on the morphological data, supported by the partial sequence of the SSU rDNA gene, we describe a new species of myxozoan, Hoferellus azevedoi n. sp.

Kudoa ajurutellus n. sp. (Multivalvulida: Kudoidae) is described as a parasite of the Bressou catfish, Aspistor quadriscutis (Siluriformes) collected at Ajuruteua beach, northeastern Pará, Brazil. The new species is described based on the morphology of the spores and the sequence of the 18S rDNA. This parasite was found only in the skeletal muscular tissue of fish hosts. In the apical view, the spores were pseudo-quadrangular in shape, with rounded borders, and four symmetrical capsules. The spores are 6.63±0.53 μm in length and 8.16±0.75 μm in width. The polar capsules are piriform, 3.45±0.30 μm in length and 1.87±0.15 μm in width. The phylogenetic analysis based on the sequence of the 18S rDNA gene indicated that the new species is clearly distinct from all other Kudoa species, and that the degree of differentiation is constant with the existence of a new species of the genus Kudoa. This is the first marine Kudoa species recorded in northeastern of the State of Pará.

Infection of fish gills by Henneguya causes greater contact between the secondary gill lamellae, thereby giving rise to decreased absorption surface area at the end of the filaments. This ectoparasite can cause damages on the gills infected fish. In the present study, fresh gills of Metynnis lippincottianus were analyzed using optical microscopy techniques. The myxoporean Henneguya sp. was found to be infecting 80% of the gills of this host fish. Presence of this parasite caused hyperplasia and fusion of the gill lamellae, but without inflammation in the parasitized organ. Resumo A infecção de Henneguya nas brânquias de peixes causam o maior contato entres as lamelas branquiais secundárias. Provoca diminuição da superfície de absorção na extremidade dos filamentos, podendo ocasionar danos as brânquias dos peixes infectados. Neste estudo foram analisadas a fresco e com técnicas de microscopia de luz as brânquias de Metynnis lippincottianus. Foi determinada a presença de mixosporídeos Henneguya sp. infectando 80% das brânquias dos peixes hospedeiros. A presença desse ectoparasito causou hiperplasia e fusão das lamelas branquiais, porém sem inflamação no órgão parasitado.

Hepatic infection involving a parasite of the family Calyptosporidae was recorded in characiform fish from the Tocantins river in the Brazilian Amazon region. In the present study, an integrated comparative analysis of morphological characteristics, histological and structural traits, and the sequence of a partial fragment of the SSUrRNA gene provides support for the identification of a new calyptosporid species, found parasitising the hepatic tissue of the fish Triportheus angulatus, collected from the Tocantins River. This new species was named Calyptospora gonzaguensis n. sp. and had ovoid oocysts with a diameter of 19.6 ± 1.4 μm and four peripheral sporocysts, 9.2 ± 0.6 μm long and 3.9 ± 0.2 μm wide, enveloped individually in fine adhesive membrane, composed of an ellipsoid body and posterior extension, with a mean length of 2.2 ± 0.4 μm.

This study describes aspects of infection caused by Myxozoa of the genus Henneguya sp. in gills of fish belonging to the species Metynnis hypsauchen. Two sampling were made in the Capim river, close to the Ribeira community, in the municipality of Ipixuna do Pará, State of Pará, Brazil, during the months of August 2018 and March 2019. The animals were captured and transported live to the Laboratório de Pesquisa Carlos Azevedo, at the Universidade Federal Rural da Amazônia (UFRA), in Belém, Pará, Brazil. The animals were examined, and after parasitism was confirmed, Differential Interference Contrast Microscopes were used, to evaluate the parasite spores. Ziehl–Neelsen stain techniques were used in histology. Necroscopic analyses of Metynnis hypsauchen specimens found parasites in 80% of the hosts (16/20), with whitish-colored cysts in the branchial filaments, containing mature spores of the genus Henneguya. The histopathological analysis indicated large areas with cystic lesions with associated ischemic necrosis. The descriptions from this study indicate that the parasite drastically compromises the host’s respiratory system. Additionally, it is worth noting that parasite fauna studies of fishes in the Capim river are still a vast topic for research; this is the first record of infection by Henneguya sp. in Metynnis hypsauchen, captured in the Capim river in Ipixuna do Pará.

A new parasite species, Kudoa yasai n. sp. (Multivalvulida), is described from the king weakfish (Macrodon ancylodon), which is an important commercial fishery resource on the Brazilian Amazon coast. A total of 190 M. ancylodon specimens were obtained from the central fish market of the town of Braganca, and pseudocysts were found in the skeletal muscle fiber samples of all (100%) of the specimens, although no inflammatory reaction was observed in any of the cases. The myxospores are quadrate in shape with four polar capsules of equal size, 6.9 ± 0.94 μm long, 8.2 ± 0.39 μm wide, and 5.5 ± 0.60 μm thick. The polar capsules are 1.8 ± 0.26 μm in length and 1.4 ± 0.18 μm in width. The morphological and morphometric parameters, together with the phylogenetic analysis of a partial sequence of the 18S (SSU rDNA) gene, all indicate conclusively that Kudoa yasai n. sp. is a new species, distinct from all other Kudoa species. The study also verified the loss of quality in the meat of the host fish (M. ancylodon) sold in the Braganca market, which reinforces the need for the more systematic control of the quality of the product and the prevention of possible health problems for the consumer.

The myxosporidians of the genus Kudoa cause post mortem myoliquefaction in fishery products and may potentially transmit zoonoses. The present study describes the infection of the skeletal musculature by Kudoa sp. in two sea catfish species, Cathorops spixii (Agassiz, 1829) and Cathorops agassizii (Eigenmann & Eigenmann, 1888), captured monthly in an estuary of the municipality of Vigia de Nazaré, in Pará, northern Brazil between March, 2015, and August, 2016. The morphological features of the spores are described, and the influence of the seasonal variation on the occurrence of the parasite is discussed. The specimens were taken to the laboratory for analysis using a hand lens and light microscopy. When parasites were identified in the musculature, small fragments of the tissue were removed for histological processing and staining by the Hematoxylin-Eosin, Ziehl-Neelsen, May Grunwald-Giemsa, and Gomori techniques. The pseudocysts were found in the muscle fibers, and the spores were star-shaped with elongated extremities and 4 piriform/rounded polar capsules of equal size. No infections were observed in the fish specimens collected during the rainy season, whereas all (100%) of the Cathorops specimens examined during the dry season were infected. This indicates that the ecology and infection patterns of the parasite (identified as a species of the genus Kudoa, on the basis of its morphological features) is influenced by salinity levels.