Graça Casal

Light and electron microscopic study of the myxosporean, Henneguya friderici n. sp. from the Amazonian teleostean fish, Leporinus friderici

A new histozoic species of myxosporean was found to infect the gill filaments, gut, kidney and liver of the freshwater teleost Leporinus friderici, collected from the estuarine region of the Amazon, near the city of Belém, Brazil. The plasmodia show asynchronous development, at any one time composed of mature spores and all sporogonic stages. The ellipsoidal spore body, measuring 10.4 microm long and 5.7 microm wide, consists of 2 equal shell valves adhering together along the straight suture line. Each valve has a caudal process measuring 23.3 microm in length. There are 2 symmetric polar capsules, without intercapsular appendix, measuring 5.0 microm x 2.1 microm, and each has a polar filament with 7-8 coils. In general, ultrastructural details of sporoblast and spore development are in agreement with previously described myxosporeans. Some ultrastructural aspects such as cellular alterations of the pericyte in the different organs infected and characterization of the sporoplasmosomes during the sporoplasm maturation are described. This parasite was studied under light and electron microscope and compared with others species of the genus Henneguya, considering also host specificity. From our observations we propose the creation of a new species, Henneguya friderici n. sp.

Ultrastructural data on the life cycle stages of Myxobolus braziliensis n. sp., parasite of an Amazonian fish

Summary A myxosporidium was found in the gills of Bunocepbalus coracoideus, a freshwater fish from the Amazon River near Belem (Brazil) and studied using light and electron microscopy. Sporogenesis follows the usual pattern known in polysporic myxosporidians, giving rise to dispone pansporoblasts. The plasmodial wall presents a very sinuous outline with projections resembling villosities, unusual for histozoic species. During valvogenesis, one of the valves in the suturai ridge curves inwards and some microtubule bundles differentiate. The sporoplasm contains numerous sporoplasmosomes with unique ultrastructural features. Based on the morphologic aspects and specificity of the host species, we propose the creation of a new species, designated Myxobolus braziliensis n. sp.

A new microsporidian parasite, Potaspora morhaphis n. gen., n. sp. (Microsporidia) infecting the Teleostean fish, Potamorhaphis guianensis from the River Amazon. Morphological, ultrastructural and molecular characterization.

A fish-infecting Microsporidia Potaspora morhaphis n. gen., n. sp. found adherent to the wall of the coelomic cavity of the freshwater fish, Potamorhaphis guianensis, from lower Amazon River is described, based on light microscope and ultrastructural characteristics. This microsporidian forms whitish xenomas distinguished by the numerous filiform and anastomosed microvilli. The xenoma was completely filled by several developmental stages. In all of these stages, the nuclei are monokaryotic and develop in direct contact with host cell cytoplasm. The merogonial plasmodium divides by binary fission and the disporoblastic pyriform spores of sporont origin measure 2.8+/-0.3 x 1.5+/-0.2 microm. In mature spores the polar filament was arranged into 9-10 coils in 2 layers. The polaroplast had 2 distinct regions around the manubrium and an electron-dense globule was observed. The small subunit, intergenic space and partial large subunit rRNA gene were sequenced and maximum parsimony analysis placed the microsporidian described here in the clade that includes the genera Kabatana, Microgemma, Spraguea and Tetramicra. The ultrastructural morphology of the xenoma, and the developmental stages including the spores of this microsporidian parasite, as well as the phylogenetic analysis, suggest the erection of a new genus and species.

Ultrastructural and phylogenetic data of Chloromyxum riorajum sp. nov. (Myxozoa), a parasite of the stingray Rioraja agassizii in Southern Brazil.

We describe a new myxozoan parasite found infecting the gall bladder of the cartilaginous fish Rioraja agassizii (Rajidae) from the South Atlantic coast of Brazil. Light microscopy, scanning and transmission electron microscopy and phylogenetic data were used. Numerous irregular polyspqric plasmodia externally covered by numerous microvilli containing different stages of sporogony, including free spores, were observed in bile. Ellipsoidal spores, on average 11.41 microm long, 8.48 microm wide and 7.32 microm thick, were formed by 2 equal-sized valves, each possessing 3 to 4 (rarely 5) elevated ridges which projected from the basal portion of the spore, and joined along a sinuous S-shaped sutural line. The basal portion of the valves bore a bundle of 33 to 37 extended tapering caudal filaments attached to the basal portion of the last ridge and basal portion of the sutural edge of the 2 valves. The caudal filaments, formed of material similar to the valves, were attached to the shell wall by a conical basis. The spores contained 4 equal-sized pyriform polar capsules (4.5 x 2.4 microm), located at the same level, each with a polar filament with 6 (rarely 7) coils. Binucleate sporoplasm was irregular in shape, with a granular matrix and dense bodies randomly distributed in a light area. Based on the shape and dimensions of the spore, on the number, position and arrangements of the surface ridges, caudal bundle of filaments, polar capsules and polar filament arrangements, as well as phylogenetic analyses using the small subunit ribosomal DNA (SSU rDNA) sequences, we propose the name Chloromyxum riorajum for this new myxozoan.

A New Species of Myxozoa, Henneguya rondoni n. sp. (Myxozoa), from the Peripheral Nervous System of the Amazonian Fish, Gymnorhamphichthys rondoni (Teleostei)

ABSTRACT. Henneguya rondoni n. sp. found in the peripheral lateral nerves located below the two lateral lines of the fish Gymnorhamphichthys rondoni (Teleostei, Rhamphichthyidae) from the Amazon river is described using light and electron microscopy. Spherical to ellipsoid cysts measuring up to 110 μm in length contained only immature and mature spores located in close contact with the myelin sheaths of the nervous fibres. Ellipsoidal spores measured 17.7 (16.9–18.1)‐μm long, 3.6 (3.0–3.9)‐μm wide, and 2.5 (2.2–2.8)‐μm (n=25) thick. The spore body measuring 7.0 (6.8–7.3)‐μm long was formed by two equal symmetric valves, each with an equal tapering tail 10.7 (10.3–11.0) μm in length. The tails were composed of an internal dense material surrounded by an external homogeneous sheath of hyaline substance. The valves surrounded two equal pyriform polar capsules measuring 2.5 (2.2–2.8)‐μm long and 0.85 (0.79–0.88)‐μm (n=25) wide and a binucleated sporoplasm cell containing globular sporoplasmosomes 0.38 (0.33–0.42) μm (n=25) in diam. with an internal eccentric dense structure with half‐crescent section. Each polar capsule contains an anisofilar polar filament with 6–7 turns obliquely to the long axis. The matrix of the polar capsule was dense and the wall filled with a hyaline substance. The spores differed from those of previously described species. Based on the ultrastructural morphology of the spore and specificity to the host species, we propose a new species name H. rondoni n. sp.

A NEW MYXOZOAN PARASITE FROM THE AMAZONIAN FISH METYNNIS ARGENTEUS (TELEOSTEI, CHARACIDAE): LIGHT AND ELECTRON MICROSCOPE OBSERVATIONS

Myxobolus metynnis n. sp. (Phylum Myxozoa) is described in the connective subcutaneous tissues of the orbicular region of the fish, Metynnis argenteus (Characidae), collected in the lower Amazon River, near the city of Peixe Boi, Pará State, Brazil. Polysporic, histozoic plasmodia were delimited by a double membrane with numerous microvilli on the peripheral cytoplasm. Several life-cycle stages, including mature spores, were observed. An envelope formed by numerous fine and anastomosed microfibrils was observed at the spore surface. The spore body presented an ellipsoidal shape and was about 13.1 μm long, 7.8 μm wide, and 3.9 μm thick. Elongated-pyriform polar capsules were of equal size, measuring 5.2 μm in length, 3.2 μm in width, and possessing a polar filament with 8–9 turns around the longitudinal axis. The binucleated sporoplasm contained a vacuole and numerous sporoplasmosomes. These were circular in cross-section, showing an adherent eccentric, dense structure, with a half-crescent section. Based on the morphological differences and host specificity, we propose that the parasite is a new species named Myxobolus metynnis n. sp.

Light and Electron Microscopy of the Spore of Myxobolus heckelii n. sp. (Myxozoa), Parasite from the Brazilian Fish Centromochlus heckelii (Teleostei, Auchenipteridae)

ABSTRACT. A myxosporean parasitizing the gill filaments of the freshwater teleost fish Centromochlus heckelii collected in the Tocantins River (Lower Amazonian Region, Brazil) is described using light and electron microscopy. This parasite produces spherical to ellipsoidal cyst‐like plasmodia up to 250 μm in diameter, with a thick wall strengthened by several stratified juxtaposed crossed collagen layers, whose thickness varies according to the number of the layers. Several compressed fibroblasts are observed among the collagen fibrils. Deposits of spherical dense material are scattered at the internal periphery of the cysts. Plasmodia and different developmental stages, including immature and mature spores, filled the central region of the cysts. The spore body is ellipsoidal in valvar view and biconvex in sutural view. It is formed by two equal‐sized and symmetric valves measuring 12.7 μm long (12.2–13.1) (n=50), 6.6 μm wide (6.3–6.9) (n=25), and 4.0 μm (3.7–4.4) (n=20) thick. A thin layer formed by fine and anastomosed microfibrils is observed at the spore surface. Two equal, elongated pyriform polar capsules measure 2.9 μm (2.7–3.3) × 1.7 μm (1.4–2.0) (n=25), each containing four or five oblique polar filament coils. The binucleated sporoplasm contains numerous spherical sporoplasmosomes, glycogen particles, and a large vacuole with fine granular matrix. Based on the morphological and ultrastructural differences and specificity of the host, we describe this isolate as a new myxosporidian, Myxobolus heckelii n. sp. (Myxozoa, Myxosporea).

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 microm in diameter) containing asynchronous developmental sporogonic stages, mainly mature spores. The spores measured 19.7 +/- 0.9 microm in total length (n = 30) and the ellipsoidal spore body was 10.8 +/- 0.5 microm long, 3.3 +/- 0.4 microm wide and 2.5 +/- 0.5 microm 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 microm 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 microm long and 1.0 +/- 0.2 microm 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.

Henneguya torpedo sp. nov. (Myxozoa), a parasite from the nervous system of the Amazonian teleost Brachyhypopomus pinnicaudatus (Hypopomidae)

A new species of Myxosporea, Henneguya torpedo sp. nov., is described from the brain and spinal cord of the Amazonian teleostean fish Brachyhypopomus pinnicaudatus collected from the Peixe Boi River, State of Park, Brazil. The spores were surrounded by a thick hyaline sheath that is homogeneous and electron translucent and consists of 2 layers of different densities. The total spore length is 48.62 +/- 0.51 microm (mean +/- SE), the ellipsoidal spore body length is 28.53 +/- 0.36 microm, the body width is 7.25 +/- 0.31 microm and the body thickness is 3.06 +/- 0.26 microm. Each of the 2 equal-sized valves presented a tapering tail (19.64 +/- 0.44 microm in length). The 2 equal-sized thin and smooth valves surrounded 2 equal-sized and elongated ellipsoidal polar capsules (6.41 +/- 0.26 x 1.84 +/- 0.19 microm) that contained 5 to 6 (rarely 7) polar filament coils. The binucleated sporoplasm contained numerous spherical sporoplasmosomes (-260 x -280 nm) with a laterally eccentric-dense structure containing a half-crescent section. The sporoplasmosomes are surrounded by a hyaline homogenous sheath. Based on the data obtained by light and electron microscopy and on the host specificity, the spores differed from the previously described Henneguya spp., mainly in the presence of a sheath surrounding the spores, the spore shape and size and the number and arrangement of the polar filament coils. Therefore, from this description we propose the establishment of a new species, which we have named Henneguya torpedo sp. nov.

Ultrastructure and phylogeny of Ceratomyxa auratae n. sp. (Myxosporea: Ceratomyxidae), a parasite infecting the gilthead seabream Sparus aurata (Teleostei: Sparidae).

A new myxosporean parasite is described from the gall bladder of the gilthead seabream Sparus aurata in a Southern Portuguese fish farm, with basis on light and transmission electron microscopy, as well as in molecular procedures. In the bile, young and mature mono- to disporic plasmodia were elliptical and presented smooth surface membranes. Crescent-shaped myxospores measured 6.7±0.7 (5.3-7.6) μm in length and 27.0±3.0 (19.7-31.2) μm in thickness. The myxospore wall was constituted by two symmetrical valves united along a slightly curved suture line, each presenting a lateral projection with a rounded end. Two equal-sized subspherical polar capsules, measuring 3.6±0.2 (2.9-3.8) μm in length and 3.5±0.3 (2.9-3.8) μm in width, were located at the same level, each displaying a polar filament coiled in 5 turns. Molecular analysis of the SSU rRNA gene confirmed the parasite as a new member of the genus Ceratomyxa, making this the fourth report of Ceratomyxa from the gall bladder of S. aurata in the Iberian Peninsula. This reinforces the assumption that species richness of ceratomyxids in South European sparids is high, but the phylogenetic analysis performed disagrees with the existence of a common ancestor for Ceratomyxa species infecting sparid hosts, as well as their clustering according to geographical location. The main Ceratomyxa clade is not monophyletic due to the inclusion of Palliatus indecorus and Pseudoalatospora kovalevae; a situation that will probably be resolved by the taxonomic revision of these genera.