Hemagglutination in gill capillaries of sheepshead, Archosargus probatocephalus (Perciformes: Sparidae), infected by a myxosporidean / Hemaglutinação em capilares branquiais de sargo-de-dente, Archosargus probatocephalus (Perciformes: Sparidae) infectado por um mixosporídeo

Abstract During a survey Myxozoa, four specimens of the sheepshead (18 ± 1.5 cm and 59 ± 2.5 g) (Archosargus probatocephalus) were collected in the Ipioquinha river (Maceió/AL). Transmission electron microscopy observations revealed erythrocyte agglutinations in gill capillaries located near spherical cysts containing myxospores of the genus Henneguya. This hemagglutination partially or totally obstructed the gill capillaries. Erythrocytes occurred in close adherence to each other, with a closed intercellular space. A few lysed erythrocytes were observed among agglutinated cells. The reduced lumen of the capillaries was partially filled with amorphous dense homogenous material adhering to the erythrocytes. In addition, heterogeneous masses of irregular lower electron density were observed in the reduced channel of the capillary. The agglutinated erythrocytes appeared dense and homogenous, lacking cytoplasmic organelles. The nuclei had the appearance of normal condensed chromatin masses, generally without visible nucleoli. This occurrence of hemagglutination only in the capillaries located in close proximity to the developing myxozoan cysts suggests that parasite development may be a factor triggering erythrocyte agglutination. This is supported by previous experimental studies that showed a probable correlation between parasitic infections and hemagglutination. Nonetheless, further studies are necessary in order to better understand the physicochemical processes involved in this phenomenon.

Resumo Durante pesquisa de mixozoários foram coletados quatro espécimes do peixes sargo-de-dente (18 ± 1.5 cm e 59 ± 2.5 g) (Archosargus probatocephalus), no rio Ipioquinha (Maceió/AL). Observações por microscopia eletrônica de transmissão revelaram aglutinação de eritrócitos em capilares branquiais localizados próximos a cistos esféricos, contendo mixosporos do gênero Henneguya. Essa hemaglutinação obstruiu parcial ou totalmente os capilares branquiais. Os eritrócitos apareceram em forte aderência entre si, com espaço intercelular fechado. Foram observados poucos eritrócitos lisados entre as células aglutinadas. O lúmen reduzido dos capilares foi parcialmente preenchido com material homogêneo denso amorfo aderido aos eritrócitos, além de massas livres heterogêneas de densidade eletrônica baixa e irregular observadas no canal reduzido dos capilares. Os eritrócitos aglutinados pareciam densos e homogêneos, sem organelas citoplasmáticas. Os núcleos apareceram como massas normais de cromatina condensada, geralmente sem nucléolos visíveis. A ocorrência de hemaglutinação apenas nos capilares, localizados nas proximidades dos cistos mixozoários, sugere que o desenvolvimento parasitário pode ser um fator desencadeante da aglutinação eritrocitária. Isso é corroborado por estudos experimentais anteriores que mostraram uma provável correlação entre infecções parasitárias e hemaglutinação. No entanto, novos estudos são necessários para melhor compreender os processos físico-químicos envolvidos neste fenômeno.

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil / Ultraestrutura de Rickettsia intracitoplasmática infectando as brânquias do teleósteo Archosargus probatocephalus (Sparidae) no Nordeste do Brasil

Abstract A histopathological survey was conducted to investigate the presence of microparasites in fish Archosargus probatocephalus in a river near Maceió, Brazil. Light microscope observations of fragments of gill showed the presence of small cysts containing numerous myxospores that were morphologically identified as Henneguya. Transmission electron microscopy observations further revealed several gill cells containing groups of prokaryotic cells within large cytoplasmic vacuoles. Each infected host cell displayed a single vacuole containing a variable number of Rickettsia-like cells (up to 11), some of which presented the dumbbell shape characteristic of binary fission. The Rickettsia-like cells were pleomorphic, without a nucleus and with chromatin dispersed in the cytoplasm. They had a thin electron-dense wall of Gram-negative type. The morphology of these prokaryotic was similar to those of the order Rickettsiales and was described as a Rickettsia-like organism. Histopathological evaluation showed that several vacuole membranes had a lysed appearance. Some had ruptured, thus allowing direct contact between the Rickettsia-like organism and the cytoplasm of the host cell. The rupturing of the branchial epithelium may have contributed towards reduction of the surface area of the gills, but it is not possible to say that this was the cause of the host's death.

Resumo Um levantamento histopatológico foi realizado para pesquisar a presença de microparasitas, no peixe Archosargus probatocephalus, em um rio próximo a Maceió, Brasil. Observações ao microscópio óptico de fragmentos de brânquias mostraram a presença de pequenos cistos contendo numerosos mixósporos, identificados morfologicamente como Henneguya. Ocasionalmente, na microscopia eletrônica de transmissão, foram observados vários corpos citoplasmáticos de inclusão, grupo aparentemente de células procarióticas que vivem dentro de um grande vacúolo citoplasmático de algumas células branquiais. As células hospedeiras infectadas tinham um único vacúolo contendo um número variável de células do tipo Rickettsia, até 11, algumas das quais em forma do haltere, característica da fissão binária. Essas células eram pleomórficas sem núcleo, tendo a cromatina dispersa no citoplasma e possuíam uma parede densa de elétrons finos do tipo Gram-negativo. A morfologia dessas células procarióticas foi semelhante àquelas da ordem Rickettsiales e foram descritas como organismos tipo Rickettsiae. A histopatologia mostra várias membranas de vacúolos circundantes com aspetos lisados, enquanto outras apresentam rupturas que mostram contato direto do organismos tipo Rickettsiae com o citoplasma da célula hospedeira. A ruptura do epitélio branquial pode ter contribuído para a redução da superfície das brânquias, mas não é possível afirmar que foi a causa da morte do hospedeiro.

Ultrastructure of phagocytes and oocysts of Nematopsis sp. (Apicomplexa, Porosporidae) infecting Crassostrea rhizophorae in Northeastern Brazil / Ultraestrutura de fagócitos e oocistos de Nematopsis sp. (Apicomplexa, Porosporidae) infectando Crassostrea rhizophorae no Nordeste brasileiro

Abstract This work describes the detailed ultrastructural morphology of the phagocyte imprisoning an oyster of Nematopsis (Apicomplexa) found in Crassostrea rhizophorae, in the city of Maceió (AL), Brazil. The highly infected hosts had half-open leaflets with weak, slow retraction of the adductor muscles. Variable number of ellipsoid oocytes, either isolated and or clustered, was found between myofibrils of the adductor muscle. Each oocyst was incarcerated in a parasitophorous vacuole of host uninucleated phagocyte. The oocysts were composed of a dense wall containing a uninucleate vermiform sporozoite. The wall of the fine oocysts was composed of homogeneous electron-lucent material formed by three layers of equal thickness, having a circular orifice-micropyle obstructed by the operculum. The oocysts presented ellipsoid morphology with their wall was surrounded by a complex network of numerous microfibrils. Important details of the taxonomic value were visualized such as the ultrastructural organization of the oocyst wall and the organization of the micropyle and operculum, beyond the microfibrils that protrude from the oocyst wall only observed by transmission electron microscopy (TEM) and that may aid in the identification of the species. However, in order to clarify the systematic position of the species reported of the genus Nematopsis, it is important to proceed with genetic analyses.

Resumo Este trabalho descreve a morfologia ultraestrutural detalhada do fagócito encarcerando um oocisto de Nematopsis (Apicomplexa) encontrado em Crassostrea rhizophorae, na cidade de Maceió (AL), Brasil. Os hospedeiros muito infectados apresentavam valvas entreabertas com retração fraca e lenta dos músculos abdutores. Número variável de oócitos de forma elipsoide, isolados e ou agrupados foi encontrado entre as miofibrilas do músculo abdutor. Cada oocisto estava encarcerado num vacúolo parasitóforo do fagócito uninucleado do hospedeiro. Os oocistos eram compostos por uma parede densa contendo um esporozoíto vermiforme uninucleado. A parede dos oocistos finos era composta de material electron-lucente homogêneo formado por três camadas de espessura igual, possuindo um orifício circular - micrópila, obstruída pelo opérculo. Os oocistos apresentavam morfologia elipsoide, sua parede era circundada por uma complexa rede de numerosas microfibrilas. Detalhes de valor taxonômico importantes foram visualizados tais como: a organização ultraestrutural da parede do oocisto e a organização da micrópila e do opérculo, além das microfibrilas que se projetam da parede do oocisto, estrutura apenas observada em microscopia eletrônica de transmissão (MET) e que pode auxiliar na identificação da espécie. Contudo, para esclarecer a posição sistemática da maioria das espécies relatadas do gênero Nematopsis é importante prosseguir com as análises genéticas.

Ultrastructural description of Ceratomyxa microlepis sp. nov. (Phylum Myxozoa): a parasite infecting the gall bladder of Hemiodus microlepis, a freshwater teleost from the Amazon River

A new ceratomyxid parasite was examined for taxonomic identification, upon being found infecting the gall bladder of Hemiodus microlepis (Teleostei: Hemiodontidae), a freshwater teleost collected from the Amazon River, Brazil. Light and transmission electron microscopy revealed elongated crescent-shaped spores constituted by two asymmetrical shell valves united along a straight sutural line, each possessing a lateral projection. The spores body measured 5.2 ± 0.4 µm (n = 25) in length and 35.5 ± 0.9 µm (n = 25) in total thickness. The lateral projections were asymmetric, one measuring 18.1 ± 0.5 µm (n = 25) in thickness and the other measuring 17.5 ± 0.5 µm (n = 25) in thickness. Two equal-sized subspherical polar capsules measuring 2.2 ± 0.3 µm in diameter were located at the same level, each possessing a polar filament with 5-6 coils. The sporoplasm was binucleate. Considering the morphometric data analyzed from the microscopic observations, as well as the host species and its geographical location, this paper describes a new myxosporean species, herein named Ceratomyxa microlepis sp. nov.; therefore representing the first description of a freshwater ceratomyxid from the South American region.

Myxidium volitans sp. nov., a parasite of the gallbladder of the fish, Dactylopterus volitans (Teleostei: Triglidae) from the Brazilian Atlantic coast: morphology and pathology

Myxidium volitans sp. nov. (Myxozoa: Myxidiidae) parasitizing the hypertrophied green-brownish gallbladder of the teleost Dactylopterus volitans, collected in the Atlantic coast near Niterói, Brazil was described based on ultrastructural studies. The spores were fusiform, sometimes slightly crescent-shaped on average 21.7 ± 0.3 µm (mean ± standard deviation) (n = 50) long and 5.6 ± 0.4 µm (n = 30) wide. The spore wall was thin and smooth, comprising two equally-sized valves joined by a hardly visible sutural ridge. Spores containing two pyriform polar capsules (PC) (5.0 ± 0.4 × 2.3 ± 0.3 µm) (n = 30) are situated in each extremity of the spore. The PC wall was composed of hyaline layer (0.20-0.29 µm thick) and by a thin external granular layer. Each PC contains a polar filament (PF) with irregular arrangements that was projected from its apical region to the bases of PC and coiled laterally from bases to the tip of PC. Some regular striations and S-like structures in the periphery of the PFs with four-five irregular sections were observed. Based on the spore morphology, ultrastructural differences and the specificity of the host we describe this parasite as a new myxosporidian, named M. volitans sp. nov.

Light and electron microscopy of Myxobolus sciades n. sp. (Myxozoa), a parasite of the gills of the Brazilian fish Sciades herzbergii (Block, 1794) (Teleostei: Ariidae)

A myxosporean parasite in the gill lamellae of the freshwater teleost fish, Sciades herzbergii (Ariidae) (Block, 1794), from the Poti River (Northeast of Brazil) was described by light and electron microscopy studies. Polysporic histozoic cyst-like plasmodia containing several life-cycle stages, including mature spores, were observed. The spores were pyriform and uninucleate, measuring 9.15 ± 0.39 ìm (n = 50) long, 4.36 ± 0.23 ìm (n = 25) wide and 2.61 ± 0.31 ìm (n = 25) thick. Elongated pyriform polar capsules (PC) were of equal size (4.44 ± 0.41 ìm long and 1.41 ± 0.42 ìm in diameter) and each contained a polar filament with 9-10 coils obliquely arranged in relation to the axis of PC. The PC wall was composed of two layers of different electron densities. Histological analysis revealed the close contact of the cyst-like plasmodia with the basal portion of the epithelial gill layer, which exhibited some alterations in the capillary vessels. Based on the morphological and ultrastructural differences, the similarity of the spore features to those of the genus Myxobolus and the specificity of this host to previously described species, we describe a new species named Myxobolus sciades n. sp. in this study.

Fine structure of Henneguya hemiodopsis sp. n. (Myxozoa), a parasite of the gills of the Brazilian teleostean fish Hemiodopsis microlepes (Hemiodontidae)

A fish-infecting myxosporean, Henneguya hemiodopsis sp. n., found infecting the gills of Hemiodopsis microlepis and collected from the Poty River near the city of Teresina, Brazil, was described based on ultrastructural studies. The parasite occurred within large whitish polysporic plasmodia (up to 200 ìm in diameter) containing asynchronous developmental sporogonic stages, mainly mature spores. The spores measured 19.7 ± 0.9 ìm in total length (n = 30) and the ellipsoidal spore body was 10.8 ± 0.5 ìm long, 3.3 ± 0.4 ìm wide and 2.5 ± 0.5 ìm thick. The spores were composed of two equal shell valves adhering together along the straight suture line, with each valve having equal-sized caudal tapering tails measuring 8.7 ± 0.6 ìm in length. The spores were surrounded by a thin anastomosed network of microfibrils, more evident on the tails. There were two symmetric elongated bottle-like polar capsules 3.5 ± 0.3 ìm long and 1.0 ± 0.2 ìm wide, each with a polar filament with five to six coils. Given the morphological and ultrastructural differences from previously described parasites and the specificity of the host species, we propose a new species, named H. hemiodopsis sp. n.

Morphological and ultrastructural redescription of Calyptospora serrasalmi Cheung, Nicrelli & Ruggieri, 1986 (Apicomplexa: Calyptosporidae), a parasite found in two new host species of the genus Serrasalmus

Coccidians are pathogenic protoparasites found in various fish species. In this report, we used light and electron microscopy to study the morphological and ultrastructural features of Calyptospora serrasalmi, a coccidian parasite found to parasitize two additional species of the teleostean genus Serrasalmus, S. striolatus and S. rhombeus, from the Amazon river and the lagoonal region of Recife, Brazil, respectively. Infection involved only the liver parenchyma, with the coccidians occurring as isolated oocysts or in clusters of up to 40-50 oocysts encapsulated by a layer of connective tissue. Several life cycle stages were observed in the same section, with oocysts being the most evident. Each spherical oocyst (~25.5 um in diameter) contained four sporocysts, each surrounded by a thin membranous veil. The sporocysts were pear-shaped (11.8x6.0 um) with an attached apical sporopodium that had several small lateral projections (up to 0.5 um long). These small projections were formed by the same material as the sporocyst wall and were distributed over the basal portion of the wall in 10-12 longitudinal series. The sporocysts lacked a Stieda body and contained two vermiform sporozoites. Calyptospora serrasalmi was distinguishable from previously described species on the basis of sporocyst morphology.

Rodlet cells from the gills and kidneys of two brazilian freshwater fishes: an ultrastructural study

Rodlet cells (RCs) are fish cells considered to be regulatory elements, ion transportation cells, secretory cells, parasitic cells, transport units of genetic material, non-specific immune cells and endogenous in nature cells. In this report, we describe the ultrastructure of RCs collected from the gills and kidneys of two species of freshwater teleosts (family Curimatidae) in Brazil: Curimata macrops Eigenmann & Eigenmann, 1889 from the Poty river, near the city of Teresina in the State of Piauí, and Curimata inornata Vari, 1989 from the Amazon river near the city of Belém in the State of Pará. A variable number of RCs was observed in these tissues, with a higher frequency in gills compared to the kidneys. No other organs were investigated. RCs were observed in healthy fish and in fish parasitized by a myxosporean of the genus Henneguya. The RCs consisted of a thick-layered capsule enclosing a variable number of small, dense rodlets surrounded by several vacuoles and a nucleus. The capsule was a cytoplasmic structure composed of thick fibrillar elements surrounded externally by the plasmalemma. The capsule and surrounding plasmalemma had a smooth, undulating surface with several microvilli projecting towards the surrounding cells. Some of the microvilli located in the apical zone of the RCs were in contact with the disorganized microfibrils of the capsules. The nucleus was located laterally or basally and showed condensed chromatin at the periphery. The ultrastructural organization of the apical zone of the RCs suggested that these cells may be involved in secretory functions. This is the first report of RCs in these two species of Brazilian fish.

Ultraestrutura de Protozoários parasitas de Peixes da região Amazônica

In this study we report some ultrastructural details of some recently described species of parasites of the phylum Myxozoa (Henneguya adherens, H. malabarica, H. striolata, H. testicularis, Tetrauronema desaequalis and Myxobolus braziliensis), found in fishes of the Amazon region. Some ultrastructural aspects of the life cycle with special reference to the spore morphology are described. The action of the parasites in host fishes is analyzed and the harmful effects of their parasitic activity are discussed.

Neste trabalho descrevemos alguns detalhes ultraestruturais de novas espécies de protoparasitas do phylum Myxozoa (Henneguya adherens, . malabarica, . striolata, . testicularis, Tetrauronema desaequalis and Myxobolus braziliensis), recentemente encontrados e descritos em peixes da bacia amazônica. São descritos os aspectos ultraestruturais do ciclo de vida dos parasitas, incluindo o esporo, vetor biológico responsável pela transmissão do parasita. Por outro lado, é analizada a ação do parasita no hospedeiro e referidos efeitos nefastos da ação parasitária.