Isofilar Polar Filament Research Articles

Paospora carinifang n. gen., n. sp. (Microsporidia: Spragueidae), a parasite of the ridgetail white prawn, Palaemon carinicauda

A new microsporidian disease of the pond-reared ridgetail white prawn, Palaemon carinicauda, was found in China. Light microscopy, pathology, and scanning electron microscopy showed that the parasite infected the host’s skeletal muscle tissue and formed spherical sporophorous vesicles (SPOVs). Electron microscopy revealed that its merogonic life stages developed in direct contact with the host cytoplasm. The sporogonic life stages underwent octosporoblastic sporogony with the formation of eight uninucleate spores in each SPOV. Fresh SPOVs were 5.4 ± 0.55 µm in diameter. The octospores were oval and measured 2.3 × 1.5 μm (fresh) and 1.96 × 1.17 μm (fixed). The isofilar polar filament was coiled with 9–10 turns and arranged in two rows. Phylogenetic analysis based on the SSU rRNA gene suggests that this microsporidium has close affinities with members of the genera Potaspora and Apotaspora, but represents an independent generic taxon. We therefore propose the establishment of a new genus and species (Paospora carinifang n. gen., n. sp.) within the family Spragueidae. We also propose a taxonomic revision to transfer Potaspora macrobrachium to this new genus and reclassify it as Paospora macrobrachium comb. nov.

Morphological characterization and genetic diversity of a new microsporidium, Neoflabelliforma dubium n. sp. from the adipose tissue of Diaphanosoma dubium (Crustacea: Sididae).

We reported a new microsporidium Neoflabelliforma dubium n. sp. from the adipose tissue of Diaphanosoma dubium in China. The infected daphnids generally appeared opaque due to the presence of numerous spore aggregates located in the adipose tissue. All developmental stages were in direct contact with the host cell cytoplasm. Multinucleate sporogonial plasmodia developed into uninucleate sporoblasts by rosette-like fashion. Mature spores were pyriform and monokaryotic, measuring 4.02 ± 0.24 (3.63-4.53) µm long and 2.27 ± 0.15 (2.12-2.57) µm wide (N = 40). The polaroplast was bipartite with a tightly packed anterior lamellae and a loosely aligned posterior lamellae. Isofilar polar filament was coiled 9-11 turns and arranged in 2-3 rows. The phylogenetic analysis based on the obtained SSU rDNA sequence indicated that the N. dubium n. sp. clustered with the freshwater oligochaete-infecting N. aurantiae to form an independent monophyletic group, positioned at the base of Clade 4. In addition, we analyzed the genetic diversity in three N. dubium n. sp. isolates based on the rDNA (SSU rDNA, ITS and LSU rDNA) and Rpb1 gene. The genetic variation among the rDNA sequences was not distinct, however, high nucleotide diversity could be observed in Rpb1 gene, and a wide variety of Rpb1 haplotypes were identified within each isolate. Genetic recombination detected in the Rpb1 sequences presumes cryptic sexual process occurring in N. dubium n. sp. Statistical evolutionary analyses further indicated that the purifying selection eliminated mutations in the Rpb1 gene.

Naidispora caidianensis n. gen. n. sp. infecting coelomocytes of oligochaete Branchiura sowerbyi (Oligochaeta: Naididae) in China

A new microsporidian parasite, Naidispora caidianensis n. gen. n. sp. was found in coelomocytes of oligochaete Branchiura sowerbyi Beddard, 1892 from Wuhan city, Hubei Province, China. Opaque, hypertrophied coelomocytes (0.17–0.24 mm in diameter) depicted clinical signs of infection. Electron microscopy revealed a microsporidian with monokaryotic life stages. Rounded uninucleate meronts subsequently transformed into multinucleate merogonial plasmodia with masses of electron-dense projections on their plasma membrane. Electron–dense sporogonial plasmodia separated into uninucleate sporonts through rosette-like budding, and further developed into sporoblasts, enclosed by a sporophorous vesicle. Uninucleate mature spores were pyriform, measured 4.1 ± 0.1 (3.9–4.3) μm × 2.1 ± 0.07 (1.9–2.2) μm (average ± SE, range, n = 50), and contained a mushroom-like anchoring disk, bipartite polaroplast, electron-lucent posterior vacuole, trilaminar spore wall and 12–14 turns of an isofilar polar filament arranged in 2–3 ranks. The 1542 bp sequence from B. soweryi showed the highest similarity (below 80 %) with Nematocenator marisprofundi (accession number: JX463178). SSU rRNA gene-based phylogenetic analysis demonstrated that the novel taxon formed an independent clade from known microsporidian parasites. Based on the ultrastructural features and SSU rRNA gene sequence, we propose the establishment of a novel genus (Naidispora n. gen.) and species (Naidispora caidianensis n. sp.) to contain this parasite.

A new isolate of Nosema fumiferanae (Microsporidia: Nosematidae) from the date moth Apomyelois (Ectomyelois) ceratoniae, Zeller, 1839 (Lepidoptera: Pyralidae).

In this study, a microsporidian pathogen of the date moth (Apomyelois (Ectomyelois) ceratoniae, Zeller, 1839) also known as the carob moth, is described based on light microscopy, ultrastructural characteristics and comparative molecular analysis. The pathogen infects the gut and hemolymph of A. ceratoniae. All development stages are in direct contact with the host cell cytoplasm. Fresh spores with nuclei arranged in a diplokaryon are oval and measured 3.29 ± 0.23 μm (4.18-3.03 μm, n = 200) in length and 1.91 ± 0.23 μm (2.98-1.66 μm, n = 200) in width. Spores stained with Giemsa's stain measured 3.11 ± 0.31 μm (3.72-2.41 μm, n = 150) in length and 1.76 ± 0.23 μm (2.16-1.25 μm, n = 150) in width. Spores have an isofilar polar filament with 10-12 coils. An 1110 bp long alignment of the current microsporidium showed an SSU rRNA gene difference of only 0.0009, corresponding to >99.91% sequence similarity with Nosema fumiferanae, while RPB1 gene sequences were 98.03% similar within an alignment of 969 bp. All morphological, ultrastructural and molecular features indicate that the microsporidian pathogen of A. ceratoniae is the new isolate of the N. fumiferanae and is named here as Nosema fumiferanae TY61.

A new microsporidium, Apotaspora heleios n. g., n. sp., from the Riverine grass shrimp Palaemonetes paludosus (Decapoda: Caridea: Palaemonidae).

We report a new microsporidium from a key species of the estuarine communities of the Gulf States, the Riverine grass shrimp, Palaemonetes paludosus. A milky-white shrimp was found in the Mobile Bay Delta, a large, oligohaline-freshwater wetland in Alabama, USA. Light microscopy of smears and thick sections of the abdominal tissues demonstrated infection with microsporidian spores enclosed in sporophorous vesicles (SVs) in sets of eight. Broadly oval spores measured 2.9 ± 0.06 × 1.7 ± 0.03 µm (2.5-3.3 × 1.6-1.9 µm, n = 11). SVs with a persistent membrane ranged from 4.4 to 5.6 µm in diameter. Subcuticular epithelium and underlying musculature were packed with sporonts, sporoblasts, and spores. Electron microscopy demonstrated diplokaryotic meronts that gave rise to sporont mother cells with a large single nucleus. The meront plasma membrane turned into a SV envelope, and the sporont wall segregated internally. The sporont nucleus underwent meiosis followed by two mitotic divisions accompanied by internal budding to produce four sporonts, each dividing in two uninucleate sporoblasts. Eight-spore SVs were filled with fibrillary-tubular secretions. Spores possessed 90-110-nm thick envelopes (exospore, 40-60 nm + endospore, 30-50 nm), a triangle-shaped nucleus, isofilar polar filament of 10-13 coils arranged in two-three rows, bipartite polaroplast, and a mushroom-shaped polar disk. The SSU rDNA sequence of the novel species was deposited in GenBank under Accession number MG 708238. SSU rDNA-based phylogenetic analysis indicated that the Riverine grass shrimp microsporidium was a new species and placed it in one branch with two species of Potaspora, xenoma-forming microsporidia from freshwater perciform fishes. Because morphological and developmental characters of the novel species did not fit the diagnosis of the genus Potaspora, and, based on SSU rDNA-inferred phylogenetic analyses, different host specificity, pathogenesis, and ecological considerations, we erect here the new genus Apotaspora for the Riverine grass shrimp microsporidium and name the new species Apotaspora heleios. Grouping together fish and crustacean parasites on SSU rDNA phylogenetic trees suggests that polyxenous life cycles might be a common feature of extinct and/or extant members of the studied lineage of the Microsporidia.

Morphology and phylogeny of Ameson portunus n. sp. (Microsporidia) infecting the swimming crab Portunus trituberculatus from China

Ameson portunus n. sp. is a new microsporidian species that infects the skeletal muscle of Portunus trituberculatus, a pond-reared swimming crab from China. This parasite was characterized using morphological and molecular phylogenetic data. Light and transmission electron microscopy revealed that this microsporidian experienced disporogonic and polysporogonic (chain-like) life cycles. Mature uninucleate spores appeared ovoid, measured 1.4±0.06×1.0±0.07μm on ultrathin sections, and exhibited no dimorphism. The isofilar polar filament was coiled in 8–9 turns. Of these coils, 5–9 were arranged in large regular outer layers; the remaining coils (0–3 coils) were situated internally. According to phylogenetic analyses based on the small subunit (SSU) rDNA gene, A. portunus n. sp. belonged to the group comprising Ameson spp. and Nadelspora canceri. The result of comprehensive analysis of ultrastructural features, molecular phylogenetic data, host and geographical differences among known species supports the establishment of a new Ameson species for this parasite. Ameson portunus n. sp. is the first Ameson species described from the coasts of East Asia.

Histological and ultrastructural study of Myxobolus mugchelo (Parenzan, 1966) with initial histopathology survey of the Liza ramada host intestine.

This paper provides histological and ultrastructural data on Myxobolus mugchelo (Myxozoa), a parasite of the intestinal wall of thinlip mullet Liza ramada from the Comacchio lagoons (Northern Adriatic Sea, Italy). About 80% of the examined mullets were infected with this myxozoan. In histological sections, the plasmodia appeared rounded to ovoid and spindle shaped, measured 181.61±97×122.79±53.16μm (mean±standard deviation, SD) in size. Early sporogenic plasmodia were located primarily in the muscle layer where no pronounced inflammatory response was detected. Plasmodia containing mature spores were situated closer to mucosal folds and were encircled by numerous immune cells, especially mast cells. Mature spores were generally oval and 6.06±0.40×3.48±0.92μm in size. The spores showed symmetrical and smooth valves. The anterior end of the spores contained two equal pyriform polar capsules measuring 2.19±0.47×1.59±0.29μm. Inside the polar capsules, an isofilar polar filament displayed 5-6 coils perpendicular or slightly oblique to the longitudinal axis. The wall of the polar capsule was filled with a hyaline substance contrasting with the very dense internal matrix. The mucus layer surrounded the spore surface. A thorough comparison with the Myxobolus species infecting intestine of fish is provided. This is the first report on occurrence of this myxozoan species in L. ramada population of the North Adriatic Sea.

Parahepatospora carcini n. gen., n. sp., a parasite of invasive Carcinus maenas with intermediate features of sporogony between the Enterocytozoon clade and other microsporidia

Parahepatospora carcini n. gen. n. sp., is a novel microsporidian parasite discovered infecting the cytoplasm of epithelial cells of the hepatopancreas of a single Carcinus maenas specimen. The crab was sampled from within its invasive range in Atlantic Canada (Nova Scotia). Histopathology and transmission electron microscopy were used to show the development of the parasite within a simple interfacial membrane, culminating in the formation of unikaryotic spores with 5–6 turns of an isofilar polar filament. Formation of a multinucleate meront (>12 nuclei observed) preceded thickening and invagination of the plasmodial membrane, and in many cases, formation of spore extrusion precursors (polar filaments, anchoring disk) prior to complete separation of pre-sporoblasts from the sporogonial plasmodium. This developmental feature is intermediate between the Enterocytozoonidae (formation of spore extrusion precursors within the sporont plasmodium) and all other Microsporidia (formation of spore extrusion precursors after separation of sporont from the sporont plasmodium). SSU rRNA-based gene phylogenies place P. carcini within microsporidian Clade IV, between the Enterocytozoonidae and the so-called Enterocytospora-clade, which includes Enterocytospora artemiae and Globulispora mitoportans. Both of these groups contain gut-infecting microsporidians of aquatic invertebrates, fish and humans. According to morphological and phylogenetic characters, we propose that P. carcini occupies a basal position to the Enterocytozoonidae. We discuss the discovery of this parasite from a taxonomic perspective and consider its origins and presence within a high profile invasive host on the Atlantic Canadian coastline.

Description and phylogeny of a new microsporidium from the elm leaf beetle, Xanthogaleruca luteola Muller, 1766 (Coleoptera: Chrysomelidae).

This study describes a new genus and species of microsporidia which is a pathogen of the elm leaf beetle, Xanthogaleruca luteola Muller, 1776 (Coleoptera: Chrysomelidae). The beetles were collected from Istanbul in Turkey. All developmental stages are uninucleate and in direct contact with the host cell cytoplasm. Giemsa-stained mature spores are oval in shape and measured 3.40 ± 0.37μm in length and 1.63 ± 0.20μm in width. These uninucleate spores have an isofilar polar filament with 11 turns. The spore wall was trilaminar (75 to 115nm) with a rugose, electron-dense exospore (34 to 45nm) and a thickened, electron-lucent endospore (65 to 80nm) overlaying the plasmalemma. Morphological, ultrastructural, and molecular features indicate that the described microsporidium is dissimilar to all known microsporidian taxa and confirm that it has different taxonomic characters than other microsporidia infecting X. luteola and is named here as Rugispora istanbulensis n. gen., n. sp.

Ultrastructural and molecular characterization of Glugea serranus n. sp., a microsporidian infecting the blacktail comber, Serranus atricauda (Teleostei: Serranidae), in the Madeira Archipelago (Portugal).

A new microsporidian infecting the connective tissue of the coelomic cavity of the blacktail comber Serranus atricauda, in the Madeira Archipelago (Portugal), is described on the basis of morphological, ultrastructural, and molecular features. The microsporidian formed large whitish xenomas adhering to the peritoneal visceral organs of the host. Each xenoma consisted of a single hypertrophic cell, in the cytoplasm of which mature spores proliferated within parasitophorous vacuoles surrounded by numerous collagen fibers. Mature spores were ellipsoidal and uninucleated, measuring an average of 6.5 ± 0.5μm in length and 3.4 ± 0.6μm in width. The anchoring disk of the polar filament was subterminal, laterally shifted from the anterior pole of the spore. The isofilar polar filament coiled in 18-19 turns, forming two rows that surrounded the posterior vacuole. The latter occupied about one third of the spore length. The polaroplast surrounding the apical and uncoiled portion of the polar filament displayed two distinct regions: a lamellar region and an electron-dense globule. Molecular analysis of the rRNA genes, including the internal transcribed spacer region, and phylogenetic analysis using maximum likelihood and neighbor joining demonstrated that this microsporidian parasite clustered with some Glugea species. Based on the differences found both at the morphological and molecular levels, to other members of the genus Glugea, the microsporidian infecting the blacktail comber is considered a new species, thus named Glugea serranus n. sp.

Tubulinosema pampeana sp. n. (Microsporidia, Tubulinosematidae), a pathogen of the South American bumble bee Bombus atratus

An undescribed microsporidium was detected and isolated from the South American bumble bee Bombus atratus collected in the Pampas region of Argentina. Infection intensity in workers averaged 8.2×107spores/bee. The main site of infection was adipose tissue where hypertrophy of adipocytes resulted in cyst-like body formation. Mature spores were ovoid and monomorphic. They measured 4.00μm×2.37μm (fresh) or 3.98μm×1.88μm (fixed). All stages were diplokariotic and developed in direct contact with host cytoplasm. Isofilar polar filament was arranged in 16 coils in one or, posteriorly, two layers. Coiling angle was variable, between perpendicular and almost parallel to major spore axis. Late meronts and sporogonial stages were surrounded by vesicles of approximately 60nm in diameter. Based on both new and already designed primers, a 1827bp (SSUrRNA, ITS, LSUrRNA) sequence was obtained. Data analyses suggest that this microsporidium is a new species of the genus Tubulinosema. The name Tubulinosema pampeana sp. n. is proposed.

Nosema pieriae sp. n. (Microsporida, Nosematidae): A New Microsporidian Pathogen of the Cabbage Butterfly Pieris brassicae L. (Lepidoptera: Pieridae)

A new microsporidian pathogen of the cabbage butterfly, Pieris brassicae is described based on light microscopy, ultrastructural characteristics and comparative small subunit rDNA analysis. The pathogen infects the gut of P. brassicae. All development stages are in direct contact with the host cell cytoplasm. Meronts are spherical or ovoid. Spherical meronts measure 3.68 ± 0.73 × 3.32 ± 1.09 µm and ovoid meronts 4.04 ± 0.74 × 2.63 ± 0.49 µm. Sporonts are spherical to elongate (4.52 ± 0.48 × 2.16 ± 0.27 µm). Sporoblasts are elongated and measure 4.67 ± 0.60 × 2.30 ± 0.30 µm in length. Fresh spores with nuclei arranged in a diplokaryon are oval and measure 5.29 ± 0.55 µm in length and 2.31 ± 0.29 µm in width. Spores stained with Giemsa’s stain measure 4.21 ± 0.50 µm in length and 1.91 ± 0.24 µm in width. Spores have an isofilar polar filament with six coils. All morphological, ultrastructural and molecular features indicate that the described microsporidium belongs to the genus Nosema and confirm that it has different taxonomic characters than other microsporidia infecting Pieris spp.

Morphology and phylogeny of Henneguya jocu n. sp. (Myxosporea, Myxobolidae), infecting the gills of the marine fish Lutjanus jocu

Henneguya jocu n. sp. (Myxosporea, Myxobolidae) is described from the gill lamellae of the marine teleost fish Lutjanus jocu, with a focus on ultrastructural and molecular features. This myxosporean forms subspherical cysts up to ∼260μm×130μm long, and develops asynchronously. Mature myxospores ellipsoidal with a bifurcated caudal process. Myxospore length 10.9±0.4μm (n=50); width, 8.2±0.3μm (n=50); and thickness, 2.9±0.5μm (n=50). Two equal caudal processes, 34.1±1.0μm long (n=50); and total myxospore length, 45.2±1.0μm (n=50). Two symmetric valves surround two ellipsoidal polar capsules, 5.0±0.3×1.4±0.2μm (n=20), each containing an isofilar polar filament forming 4–5 coils along the inner wall of these structures, as well as a binucleated sporoplasm presenting a spherical vacuole and several globular sporoplasmosomes. Both the morphological data and molecular analysis of the SSU rDNA gene identify this parasite as a new species of the genus Henneguya. Maximum Likelihood and Maximum Parsimony analyses further indicate that the parasite clusters within others marine Myxobolidae species, forming a group alongside other Henneguya species described from marine hosts.

A new intranuclear microsporidium, Enterospora nucleophila n. sp., causing an emaciative syndrome in a piscine host (Sparus aurata), prompts the redescription of the family Enterocytozoonidae

The presence of a new microsporidium is believed to be responsible for an emaciative syndrome observed in farmed gilthead sea bream (Sparus aurata) from different facilities along the Spanish coast. Infected fish were approximately half the average weight and significant mortality was attributed to the condition in some facilities. Clinical signs included anorexia, cachexia and pale internal organs. The microsporidium was found mainly in the intestinal mucosa and occasionally in the submucosa. Morphological, histopathological, ultrastructural and molecular phylogenetic studies were conducted to characterise this organism. This microsporidium undergoes intranuclear development in rodlet cells and enterocytes, and cytoplasmic development mainly in enterocytes and macrophages. The nucleus-infecting plasmodium contains several diplokarya and displays polysporous development which occurs without an interfacial envelope. In the host cell cytoplasm, the parasite develops within a membrane-bound matrix. In both infection locations, the polar tube precursors appear as disks, first with lucent centres, then as fully dense disks as they fuse to form the polar filament, all before division of the plasmodium into sporoblasts. Up to 16 intranuclear spores result from the sporogonic development of a single plasmodium, whereas more than 40 spores result from several asynchronous reproductive cycles in the cytoplasmic infection. Fixed spores are ellipsoidal and diplokaryotic, with five to six coils of an isofilar polar filament in a single row. ssrDNA-based molecular phylogenetic inference places this parasite as a sister clade to crustacean-infecting species of the Enterocytozoonidae and closer to Enterocytozoon bieneusi than to other fish-infecting microsporidians presenting intranuclear development, i.e. Nucleospora, Paranucleospora and Desmozoon. Our studies result in the erection of a new species, Enterospora nucleophila, within the family Enterocytozoonidae, and the description of this family is amended accordingly to accommodate the features of known species assigned to it. Severe histopathological damage occurs in intense infections and this microsporidian is considered a serious emerging threat in sea bream production.

Multilamina teevani gen. et sp. nov., a microsporidian pathogen of the neotropical termite Uncitermes teevani

A new genus and species of microsporidia is described from adults of the termite Uncitermes teevani (Emerson) (n. comb., formerly Armitermes teevani), collected in Ecuador. Masses of elongate, ovoid, uninucleate spores were localized to the coelomic cavity of adult workers and measured 6.29×3.33μm (fresh) and 5.83×3.00μm (fixed). These spores were individually contained within a multi-layered sporophorous vesicle and contained an isofilar polar filament with 24–28 coils. Blast-n analysis revealed that the small subunit ribosomal DNA (ssrDNA) sequence of this new species exhibited 85% identity with that of a Varimorpha species from the fire ant, Solenopsis richteri, and slightly less (78–85% identity) to a large clade of microsporidian parasites from mosquitoes and microcrustacea. The morphological and sequence data support the conclusion that Multilamina teevani gen. et sp. nov. is a novel microsporidium and distinct from any previously described genera or species.

Ultrastructure and molecular characterization of the microsporidium, Nosema chrysoperlae sp. nov., from the green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) used for biological pest control

Lacewing larvae are generalist predators that are commercially available for aphid control on a variety of crops in both Europe and North America. Although lacewings are known for their symbiotic association with yeasts and bacteria, there are few reports of microsporidia in these natural enemies. An undescribed microsporidium was found in Chrysoperla carnea (Stephens) during the routine examination of specimens that were obtained from a commercial insectary for biological pest control. The objective of this study was to describe the pathogen by means of ultrastructure, molecular characterization and tissue pathology. All stages of the microsporidium were diplokaryotic and developed in direct contact with the host cell cytoplasm. Merogony and sporogony were not observed. Mature spores measured 3.49±0.10×1.52±0.05μm and had an isofilar polar filament with 8–10 coils that were frequently arranged in a single row, although double rows were also observed. Spores contained a lamellar polaroplast and a relatively small and inconspicuous polar vacuole was observed in the posterior region of about half of the spores that were examined. Tubular structures, similar in appearance to those in Nosema granulosis were observed in both sporonts and in spores. A cluster of small tubules was also observed in the posterior region of some spores. Microsporidian spores were observed in cells of the proventriculus, diverticulum and in epithelial cells of the posterior midgut. The Malpighian tubules, ileum, and rectum were heavily infected. Spores were also observed in the fat body, peripheral region of the ganglia, within and between the flight muscles, and beneath the cuticle. Although the tissues adjacent to the ovaries were heavily infected, microsporidian spores were not observed within the developing eggs. Pathogen transmission was not studied directly because it was difficult to maintain microsporidia-infected C. carnea in the laboratory. The presence of microsporidian spores in the alimentary canal suggests that the pathogen is transmitted per os and horizontal transmission may occur when infected larvae or adults are cannibalized by uninfected larvae. Molecular analysis of the microsporidian genome showed that the pathogen described in this study was 99% similar to Nosema bombycis, N. furnacalis, N. granulosis and N. spodopterae. Based on information gained during this study, we propose that the microsporidium in C. carnea be given the name Nosema chrysoperlae sp. nov.

Morphological and Molecular Characterization of a New Myxozoan Species (Myxosporea) Infecting the Gall Bladder ofRaja clavata(Chondrichthyes), from the Portuguese Atlantic Coast

Microscopic and molecular procedures are used to describe a new myxosporean species, Chloromyxum clavatum n. sp., infecting the cartilaginous fish Raja clavata Linnaeus, 1758 (Chondrichthyes: Rajidae), collected from the northwest Atlantic coast of Portugal. Young plasmodia and mature spores were found floating free in the gall bladder of R. clavata . Spores were spherical to subspherical with a pointed anterior end, measuring14.4 ± 0.5 μm (n = 25) in length, 11.9 ± 0.5 μm (n = 25) in width, and 9.4 ± 0.5 μm (n = 15) in thickness. The spore's wall was composed of 2 equally sized valves, each displaying 6-8 elevated surface ridges and a bundle of several tapering caudal filaments attached to the basal portion. Spores contained 4 pyriform equally sized polar capsules (5.5 ± 0.4 μm × 2.9 ± 0.5 μm) (n = 25), each possessing an obliquely arranged isofilar polar filament coiled in 7-8 coils. Morphological data, host specificity, tissue tropism, and molecular analysis of the SSU rDNA gene identify this parasite as a new species of Chloromyxum. Neighbor-joining and maximum likelihood further reveal the parasite clustering with other species of Chloromyxum infecting the gall bladder of marine cartilaginous fish to form a clade positioned at the base of the freshwater clade, therefore constituting an exception to the major division of the class Myxosporea into the freshwater and marine clades, while supporting the existence of a correlation between tissue tropism and myxosporean phylogeny.

Ultrastructural and molecular studies of Microgemma carolinus n. sp. (Microsporidia), a parasite of the fish Trachinotus carolinus (Carangidae) in Southern Brazil

A new species of Microsporidia Microgemma carolinus n. sp. found in the marine teleost Trachinotus carolinus collected in Florianópolis, Brazil was described based on light, ultrastructural and phylogenetic studies. This parasite developed in the liver forming whitish xenomas that contained different developmental stages with monokaryotic nuclei. The periphery of the xenoma presented some vacuolization and possessed several small projections in the membrane. The mature spores, measuring 3·8 ± 0·4 μm in length and 2·4 ± 0·4 μm in width, were slightly pyriform to ellipsoidal and had rounded ends. The polaroplast was bipartite and the isofilar polar filament was coiled with 8 - 9 turns in a single or double row at the posterior end of the spore. The nucleus was voluminous and in a central position, measuring ~0·9 μm in diameter. A large posterior vacuole appeared as a pale area, occupying about a third of the spore length. The SSU rRNA gene was sequenced and analysed using maximum parsimony, maximum likelihood and neighbour-joining methods. This study allowed us to conclude that this was a new species of the genus Microgemma, being the first description of this genus from among South America fauna.

Redefining the genus Spraguea based on ultrastructural and phylogenetic data from Spraguea gastrophysus n. sp. (Phylum Microsporidia), a parasite found in Lophius gastrophysus (Teleostei) from Brazil

The ultrastructure of the fish-infecting microsporidium Spraguea gastrophysus found in the dorsal ganglia and kidney of the anglerfish, Lophius gastrophysus (family Lophiidae) collected on the Brazilian Atlantic coast is described. Each whitish xenoma (up to 3.1 × 1.8 mm) contains several groups of parasites. The host cells are hypertrophied and contain various parasite life stages including mature spores and several developmental stages with unpaired nuclei. Monomorphic spores are ellipsoidal, lightly curved and measure about 3.35 × 1.71 μm. The spore contains a gradually tapering isofilar polar filament with five to six coils arranged in a single row. The nucleus occupies a central zone of the sporoplasm where also several polyribosomes are presented. The posterior vacuole contains a voluminous spherical and granular posterosome measuring up to ~0.65 μm in diameter. The partial small subunit, intergenic spacer and partial large subunit rRNA gene were sequenced and the phylogenetic analysis places the microsporidian described here in the clade that includes all sequences of the Spraguea genus. The ultrastructural morphology of the xenoma and the spores of this microsporidian parasite, as well as the molecular and phylogenetic analysis, suggest the description of a new species. A redefining of the genus Spraguea is also done.

Ultrastructure and molecular phylogenetics of Helmichia lacustris, a microsporidium with an uncoiled isofilar polar filament

The description of Helmichia lacustris Voronin (Parazitologiya 34:327-331 1998) is supplemented with morphogenesis and ultrastructure of the extrusion apparatus. Formation of the anterior (made up by rare short lamellae) and posterior (made up by spongy matter or small vesicles) regions of the polaroplast is preceded by granulated spheres and agglomerations of bean-like bodies, respectively. The anchoring disc is formed by an oval structure of moderate electron density, sometimes possessing a granular texture. The parasite development occurs within the cisterns of granular endoplasmatic reticulum (ER) of the host cell. Each group of spores is enclosed within a two-layered sheath, including the smooth inner membrane of the sporophorous vesicle and the outer ribosome-encrusted membrane (which originates from the host cell ER) of the parasitophorous vacuole. Two microsporidia, H. lacustris (GenBank accession number GU130406) and Euplotespora binucleata (GenBank accession number DQ675604) share 78.1% of 16S rRNA gene sequence similarity. Both parasites are characterized by an uncoiled isofilar polar filament. They form a cluster nested among terrestrial and aquatic microsporidia with well-developed coiled polar filaments, suggesting that an uncoiled polar filament in this species is a result of reduction, rather than a "primitive" character.