Phylogeny,ultrastructure and histopathology of Myxobolus lomi sp. nov., a parasite of Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) from the Peixes River,São Paulo State,Brazil

This paper presents the morphological, histological, molecular and ultrastructural data on Myxobolus lomi sp. nov., a parasite of the gill filaments of Prochilodus lineatus from the Peixes River (48º06′38″W; 22º 49′53.1″S), São Paulo State, Brazil. From 20 P. lineatus specimens examined, 90.0% (n = 18) were infected. The plasmodia were white and round, measuring 250 to 300 μm in diameter and the development occurred in the base of the gill filament. The spores showed symmetrical and smooth valves, with the polar filament having 8 to 11 coils. A thorough comparison with all the Myxobolus species described so far is provided. A partial sequencing of the 18S rDNA gene revealed approximately 1600-bp. The Myxobolus species parasite of P. lineatus did not match any of the Myxozoa available in GenBank. In the phylogenetic analysis, M. lomi sp. nov. is clustered with ten other species and only four of these parasites were from gills. Histological analysis of P. lineatus gills infected by M. lomi sp. nov. revealed numerous well-delimited cysts at the base of the primary lamella, between connective tissue and bone, next to the gill arteries. However no pronounced inflammatory response was found at the infection site.     

Some remarks on the occurrence,host-specificity and validity of <Emphasis Type="Italic">Myxobolus rotundus</Emphasis> Nemeczek, 1911 (Myxozoa: Myxosporea)

Myxobolus rotundus Nemeczek, 1911 is a common and specific parasite of the common bream Abramis brama (L.). Small, round or ellipsoidal shaped plasmodia of this species develop in the gill and exhibit strong histotropism to the secondary gill lamellae with plasmodial development in their capillary network. M. rotundus is frequently found in mixed infection with M. bramae Reuss, 1906, a parasite of the afferent arteries of gill filaments. The round spores of M. rotundus resemble several other Myxobolus spp., but can be distinguished from these by their small subunit ribosomal RNA gene sequence (GenBank accession no. EU710583), which also differs from the sequence for ‘M. rotundus’ from the skin of Chinese goldfish Carassius auratus auratus (L.), which we suggest has been misidentified. The SSU rRNA gene sequence of M. rotundus myxospores from bream corresponded to Triactinomyxon type 4 actinospores (AY495707) isolated from Tubifex tubifex (Müller) by Hallett et al. (2005), and we infer from this that these are alternate life stages.     

Life Cycle of Culicosporella lunata (Hazard & Savage, 1970) Weiser, 1977 (Microspora) as Revealed in the Light Microscope with a Redescription of the Genus and Species1

Light microscopy studies of Culicosporella lunata (Hazard & Savage), a parasite of the mosquito Culex pilosus (Dyar & Knab), revealed two sporogonial sequences. One sequence begins with diplokaryotic meronts that undergo repeated nuclear divisions to produce sporogonial plasmodia with nuclei in diplokaryotic arrangement. These plasmodia form rosette-like clusters of sporoblasts during incomplete cytokinesis and, eventually, binucleate spores. These spores initiate infections in healthy larvae when they ingest spores. The second sequence begins with diplokaryotic meronts that undergo karyogamy and meiosis to form Thelohania-like sporonts and haploid spores. Anomalies are often observed in these sporonts which result in aberrant spores, usually fewer than eight, in an accessory (pansporoblastic) membrane. Normal haploid spores are morphologically similar to those of species of Amblyospora. The genus and the type species are redefined based on new information presented here and it and the type species are placed in the family Amblyosporidae.     

Henneguya tunisiensis n. sp. (Myxosporea: Bivalvulida), a new gill parasite of Symphodus tinca (L.) (Teleostei: Labridae) off Tunisia

Henneguya tunisiensis n. sp., a new myxosporean, is described from the gill-arches of the East Atlantic peacock wrasse Symphodus tinca (L.) collected from off the Kerkennah Islands, Tunisia. It is characterised by the presence of elongate white plasmodia of 1–1.5 × 1.5–2 mm in size. The mature spores are rounded in frontal view and have two identical polar capsules and two caudal appendages which taper considerably at the end. Both light and electron microscopical data show that this species differs in several morphological features from all previously described Henneguya spp. A molecular analysis, based on 18S rDNA sequence data, indicates that H. tunisiensis n. sp. is readily distinguishable from other myxozoan DNA sequences in GenBank. Phylogenetically, the new species is placed in the marine Henneguya clade, which is a sister group of marine Myxobolus spp. from perciform fishes in Tunisian waters.     

Morphological,histological and molecular characterization of three Myxobolus species (Cnidaria: Myxosporea) from silver carp Hypophthalmichthys molitrix Valenciennes and bighead carp Hypophthalmichthys nobilis Richardson in China

Three Myxobolus species were obtained from silver carp Hypophthalmichthys molitrix Valenciennes and bighead carp Hypophthalmichthys nobilis Richardson in China. In the present study, we supplemented their taxonomic characteristics by the morphological, histological and molecular methods. Myxobolus kiuchowensis Chen in Chen et Ma, 1998 formed small ellipsoidal plasmodia in the intestinal wall of bighead carp. Its spores appeared asymmetrical obovate in frontal view and fusiform in lateral view. Tiny mamillary protrusion in the anterior of some spores was observed. Two pyriform polar capsules were unequal. Histologically, M. kiuchowensis infected the tunica muscularis of host intestine. Myxobolus abitus Li et Nie, 1973 formed sausage–like plasmodia in the gills of silver carp. Its spores appeared oblate in frontal view and fusiform in lateral view. Two pyriform polar capsules were unequal and an obvious inter–capsule appendix was observed. Histological examination revealed that M. abitus developed in the interlamellar–epithelium of host gills. Myxobolus pavlovskii (Akhmerov, 1954) Landsberg et Lom, 1991 formed sausage–like plasmodia both in the gills of silver carp and bighead carp. Spores of M. pavlovskii were proximate oval in frontal view and fusiform in lateral view. Two pyriform polar capsules were unequal. The BLAST search indicated the SSU rDNA sequences of M. kiuchowensis and M. abitus were not identical to any sequence, however, the SSU rDNA sequences of M. pavlovskii were identical to that of M. pavlovskii recorded previously. Phylogenetic analysis showed that the present three species robustly clustered together in Cyprinid group and Asia group.     

Histological and molecular studies of species of Myxobolus Bütschli, 1882 (Myxozoa: Myxosporea) in the gills of Abramis, Blicca and Vimba spp. (Cyprinidae), with the redescription of M. macrocapsularis Reuss, 1906 and M. bliccae Donec & Tozyyakova, 1984

Although Myxobolus spp. from cyprinid fishes are generally characterised by a strict host-specificity, this study has found that the breams Abramis brama (L.), Blicca bjoerkna (L.) and Vimba vimba (L.) may be infected by the same Myxobolus spp. It is demonstrated that M. macrocapsularis Reuss, 1906, a parasite of the gill filaments of B. bjoerkna, can also infect A. brama. In the same way, M. bliccae Donec & Tozyyakova, 1984, also a parasite of B. bjoerkna, can also occur in V. vimba. The molecular sequences of M. macrocapsularis spores from B. bjoerkna and A. brama were 100% identical. Two of the 18S rDNA sequences of three replicate samples of M. bliccae from B. bjoerkna were 100% identical, whereas the third sequence exhibited a 99.7% similarity with sequences from V. vimba. M. bliccae sequences of spores collected from V. vimba showed a 99.8% similarity to the first two isolates and 99.6% to the third. Data obtained by morphological, histological and molecular biological methods all suggest that Myxobolus spp., known for their strict host-specificity, may sometimes infect several closely related cyprinids.     

Maullinia ectocarpii gen. et sp. nov. (Plasmodiophorea), an Intracellular Parasite in Ectocarpus siliculosus (Ectocarpales, Phaeophyceae) and other Filamentous Brown Algae

An obligate intracellular parasite infecting Ectocarpus spp. and other filamentous marine brown algae is described. The pathogen forms an unwalled multinucleate syncytium (plasmodium) within the host cell cytoplasm and causes hypertrophy. Cruciform nuclear divisions occur during early development. Mature plasmodia become transformed into single sporangia, filling the host cell completely, and then cleave into several hundred spores. The spores are motile with two unequal, whiplash-type flagella inserted subapically and also show amoeboid movement. Upon settlement, cysts with chitinous walls are formed. Infection of host cells is accomplished by means of an adhesorium and a stachel apparatus penetrating the host cell wall, and injection of the cyst content into the host cell cytoplasm. The parasite is characterized by features specific for the plasmodiophorids and is described as a new genus and species, Maullinia ectocarpii.     

HETEROTHALLISM AND HOMOTHALLISM IN TWO MYXOMYCETES

Collins , O'Neil Ray . (Queens Coll., New York City.) Heterothallism and homothallism in two Myxomycetes. Amer. Jour. Bot. 48(8): 674–683. Illus. 1961.—Single-spore studies of 2 Myxomycetes, Didymium iridis and Fuligo cinerea, revealed that the former is heterothallic and the latter is homothallic. In D. iridis, 256 single-spore isolations were made from sporangia which developed in mass-spore cultures. Of these, 101 germinated and 22 yielded plasmodia that later fructified in most cases. The remaining 79 single-spore cultures produced clones of myxamoebae and swarm cells only. When 18 of the 79 clones were mated in all possible combinations, plasmodia developed in a pattern which showed that the clones were either (+) or (–) with regard to mating type. Fructifications were readily obtained from these plasmodia. Fifty-three single spores of the F₁ generation were isolated. Of the 44 that germinated, 9 yielded plasmodia in monospore cultures, and 35 produced clones of myxamoebae and swarm cells only. Twenty-five of the F₁ clones were back-crossed with their parents. Results of the back crosses show that each F₁ clone is capable of yielding plasmodia with either the (+) or the (–) parent, never with both. When 14 of the F₁ clones were mated among themselves, a (+) and (–) mating type system was again revealed. Most of the 22 original single-spore cultures which produced plasmodia, later formed sporangia. From these sporangia, 88 spores were isolated. Seventy-two of these germinated and yielded large populations of swarm cells and myxamoebae, but none produced plasmodia. Twenty of the 72 clones were then mated among themselves. Some matings resulted in plasmodial formation, but the pattern was difficult to interpret. However, when these 20 clones were mated with known (+) and (–) clones, the results appear to be in keeping with a (+) and (–) mating type system. In F. cinerea, 219 single spores were isolated from aethalia derived from mass-spore cultures. Of these, 144 germinated and the same number yielded plasmodia. Fructifications were easily obtained from such plasmodia. Thirty-five second-generation single spores were isolated, of which 15 germinated and 15 yielded plasmodia. These results indicate that F. cinerea is homothallic.     

Morphologic and Genetic Evidence for Mixed Infection with Two Myxobolus Species (Myxozoa: Myxobolidae) in Gray Mullets,Mugil cephalus,from Korean Waters

The present study was performed to trace the decisive evidence for mixed infection of 2 Myxobolus species, M. episquamalis and Myxobolus sp., in the gray mullet, Mugil cephalus, from Korean waters. Mullets with whitish cyst-like plasmodia on their scales were collected near a sewage plant in Yeosu, southern part of Korea, in 2009. The cysts were mainly located on scales and also found in the intestine. The spores from scales were oval in a frontal view, tapering anteriorly to a blunt apex, and measured 7.2 µm (5.8-8.0) in length and 5.3 µm (4.7-6.1) in width. Two polar capsules were pyriform and extended over the anterior half of the spore, measuring 3.5 µm (2.3-4.8) in length and 2.0 µm (1.5-2.2) in width. In contrast, the spores from the intestine were ellipsoidal, 10.4 µm (9.0-11.9) in length and 8.4 µm (7.3-10.1) in width. The polar capsules were pyriform but did not extend over the anterior half of the spore, 3.7 µm (2.5-4.5) in length and 2.2 µm (1.8-2.9) in width. The nucleotide sequences of the 18S rDNA gene of the 2 myxosporean spores from scales and intestine showed 88.1% identity to each other and 100% identity with M. episquamalis and 94.5% identity with M. spinacurvatura from mullet, respectively. By the above findings, it is first confirmed that mullets from the Korean water are infected with 2 myxosporean species, M. episquamalis and Myxobolus sp.     

Phylogeny of Myxobolidae (Myxozoa) and the evolution of myxospore appendages in the Myxobolus clade

Genera Myxobolus Bütschli, 1882 and Henneguya Thélohan, 1892 (Myxobolidae) are specious myxozoan genera. They comprise nearly half of overall known myxozoan species diversity. A typical spore feature of Henneguya is the presence of two caudal appendages of the spore valves, which distinguishes them from species of the genus Myxobolus. Several Myxobolus spp., however, were reported to show aberrant spores with Henneguya-like caudal appendages. We found such aberrant spores in Myxobolus tsangwuensis and Myxobolus wulii. We studied the ultrastructure of M. wulii and Myxobolus oralis spores with caudal appendages by transmission electron microscopy (TEM). TEM of these aberrant spores revealed that their caudal appendages have the same ultrastructure as the appendages of Henneguya spp. Small caudal appendages of M. wulii spores observed only on TEM suggested that this character may be often overlooked and more Myxobolus species potentially have the ability to express the caudal appendages on the myxospore. In order to trace the evolution of this character, we performed broad phylogenetic analysis of all species of the family Myxobolidae which are available in GenBank including nearly 300 taxa. We found at least eight independent evolutionary origins of spores with two appendages, three origins of a single appendage and 12 apparent secondary losses of the spore projections. Therefore, genus Henneguya with typical two-tailed myxospores is polyphyletic, however a majority of its species has a common ancestor and groups in the second largest subclade of the Myxobolus clade. We also mapped the biological characteristics (host, site of infection and environment) of Myxobolidae species on the phylogenetic tree. We revealed an evident host-associated evolutionary pattern in all parts of the Myxobolus clade with a distinct and species-rich subclade containing almost exclusively species infecting species of the Order Cypriniformes.     

Ultrastructural and Cytochemical Observations on Sporogenesis of Myxobolus sp. (Myxosporida: Myxobolidae) from the Common Shiner Notropis cornutus*

SYNOPSIS. The structure and cytochemistry of spores of Myxobolus sp. from plasmodia which occur in the gill filaments of the common shiner Notropis cornutus were studied by light microscopy and by scanning and transmission electron microscopy. The thin-walled valves of the pyriform spores are thickened in the lateral sutural and apical regions. Mucous material is associated predominantly with the posterior end of many spores. The plasmodium is surrounded by a syncytial wall bounded by 2 membranes. Pinocytotic channels are formed by the inner membrane and numerous dense vesicles are pinched off at the distal ends of the channels. Sporogenesis is initiated by the envelopment of one vegetative cell by another. The larger, enveloped cell divides to form a disporous pansporoblast, which contains 2 pairs of capsulogenic and valvogenic cells and 2 binucleate sporoplasm cells. Each capsular primordium and connecting external tubule gives rise to a polar capsule which houses a helically coiled polar tubule. The apical end of each polar capsule is plugged by a stopper. The valvogenic cells surround the capsulogenic and posteriorly situated sporoplasm cells to form the spore valves. Iodinophilic (glycogen) inclusions were not seen in spores stained with iodine or Best's carmine. A darkly stained band was observed around the posterior region of most spores stained with Best's carmine. In the electron microscope large aggregates of β glycogen particles were seen in the cytoplasm of sporoplasm cells in mature spores.     

Enterocytozoon hepatopenaei sp. nov. (Microsporida: Enterocytozoonidae), a parasite of the black tiger shrimp Penaeus monodon (Decapoda: Penaeidae): Fine structure and phylogenetic relationships

A new microsporidian species, Enterocytozoon hepatopenaei sp. nov., is described from the hepatopancreas of the black tiger shrimp Penaeus monodon (Crustacea: Decapoda). Different stages of the parasite are described, from early sporogonal plasmodia to mature spores in the cytoplasm of host-cells. The multinucleate sporogonal plasmodia existed in direct contact with the host-cell cytoplasm and contained numerous small blebs at the surface. Binary fission of the plasmodial nuclei occurred during early plasmodial development and numerous pre-sporoblasts were formed within the plasmodium. Electron-dense disks and precursors of the polar tubule developed in the cytoplasm of the plasmodium prior to budding of early sporoblasts from the plasmodial surface. Mature spores were oval, measuring 0.7 × 1.1 μm and contained a single nucleus, 5-6 coils of the polar filament, a posterior vacuole, an anchoring disk attached to the polar filament, and a thick electron-dense wall. The wall was composed of a plasmalemma, an electron-lucent endospore (10 nm) and an electron-dense exospore (2 nm). DNA primers designed from microsporidian SSU rRNA were used to amplify an 848 bp product from the parasite genome (GenBank FJ496356). The sequenced product had 84% identity to the matching region of SSU rRNA from Enterocytozoon bieneusi. Based upon ultrastructural features unique to the family Enterocytozoonidae, cytoplasmic location of the plasmodia and SSU rRNA sequence identity 16% different from E. bieneusi, the parasite was considered to be a new species, E. hepatopenaei, within the genus Enterocytozoon.     

Ultrastructure of Triangulamyxa amazonica n. gen. and n. sp. (Myxozoa, Myxosporea), a parasite of the Amazonian freshwater fish, Sphoeroides testudineus (Teleostei, Tetrodontidae)

Triangulamyxa amazonica n. gen. and n. sp. (Myxozoa, Ortholineidae), found in the lumen of the intestine of the freshwater fish Sphoeroides testudineus, is described. The fish were collected from the Amazon River near the city of Algodoal, State of the Pará, Brazil. Numerous irregular plasmodia containing different stages of sporogony, including spores, were observed. The plasmodia were lying free in the lumen or had slender pseudopodia-like cytoplasmic processes in contact with intestinal epithelial cells with microvilli projections. Spores, which are equilaterally triangular in valvar view with rounded pointed ends and ellipsoidal in transverse section, are 8.5 μm long, 7.6 μm wide, and 3.8 μm thick. The anterior end of the spores contains two equal drop-shaped polar capsules measuring 2.6 μm in length, each having an isofilar polar filament with 5–6 turns. The characteristics of the spore shape, the spore wall structure and its ridge organization, the plasmodial characteristics and the identity of the host suggest that the parasite is a new genus and species, which is herein designated T. amazonica.     

Myxosporean Infections in Cultured Tilapias in Israel1

Five new species of myxosporean parasite are described from cultured tilapias in Israel. These are: Myxosoma sarigi. Myxosoma equatorialis, Myxobolus israelensis. Myxobolus agolus, and Myxobolus galilaeus. The first four were found in hybrids of Oreochromis aureus x Oreochromis niloticus while Myxobolus galilaeus was found in Sarolherodon galilaeus. In addition, M. sarigi. M. israelensis, and Myxobolus sp. were also found in S. galilaeus. In the light of the present study, the taxonomy of myxosporean infections in tilapias is modified. Mature spores may localize in the melano-macrophage centers of the spleen and kidney where ihey may eventually be destroyed. Nc cases of mortality have so far been associated with these parasites.     

Ceratomyxa hungarica n. sp. and Chloromyxum proterorhini n. sp. (Myxozoa: Myxosporea) from the freshwater goby Proterorhinus marmoratus (Pallas)

When studying the parasite fauna of freshwater gobies Proterorhinus marmoratus collected from the reaches of the River Danube around Budapest, two species of Myxosporea were recovered, a renal and a gall-bladder form. Previously no myxosporeans had been reported from this fish species. The spores and pseudoplasmodia of the parasite described as Ceratomyxa hungarica n. sp. were found in the convoluted tubules of the kidney and in the cavity of Bowman's capsule. The pseudoplasmodia were loosely attached to the wall of the tubules, causing their distention. Within each pseudoplasmodium two spores were formed. In the case of Chloromyxum proterorhini n. sp. only spores floating freely in the contents of the gall-bladder were found. Since Ceratomyxa species are typically marine fish parasites, Proterorhinus marmoratus, a fish species which has adapted to freshwater, appears to have retained some of its marine myxosporean fauna.     

STUDIES ON THE LIFE CYCLE AND TAXONOMY OF LIGNIERA VERRUCOSA

Miller , Charles E. (A. and M. College of Texas, College Station.) Studies on the life cycle and taxonomy of Ligniera verrucosa. Amer. Jour. Bot. 46(10): 725–729. Illus. 1959.—A study of the roots of Veronica persica Poir. and V. hederaefolia L. plants infected with Sorosphaera veronicae Schroeter revealed intracellular cystosori and zoosporangial sori of Ligniera verrucosa. The zoosporangial phase of this species has been heretofore unknown. The plasmodia of L. verrucosa occur in root hairs, and other epidermal and sub-epidermal cells of the roots. Zoosporangial and cystosoral plasmodia are indistinguishable until cleavage has started. It is thought that plasmodia produced during early infection develop into zoosporangia, while those produced later develop into resting spores. Zoospores discharged from zoosporangia may reinfect host cells developing there into zoosporangial or cystosoral plasmodia. No evidence for any sexual process was observed. The spherical zoosporangia making up a single zoosporangial sorus may be interconnected; a single discharge pore may serve to liberate zoospores from different zoosporangia. In the Plasmodiophorales the classical basis for generic distinction has been the arrangement of the resting spores in the sorus. Ligniera, because of the supposedly uncharacteristic nature of its cystosori, has been suggested as a host-variety of Sorosphaera. A comparative study of the cystosori and zoosporangia of Ligniera and Sorosphaera growing in a single host has led to the conclusion that these genera should be considered distinct.     

Species of the genus Chloromyxum Mingazzini (Myxozoa: Myxosporea) infecting burbot (Lota lota L.)

Three different species of the genus Chloromyxum Mingazzini were found in burbot (Lota lota L.) collected in south-west Bohemia (Czechoslovakia). Comparison with existing records revealed that one species could be identified as C. pseudomucronatum Kashkovskiy, 1966. Found in the urinary bladder, it had subspherical spores with fine surface ridges and polysporic plasmodia. The two other myxosporea were established as new species: C. lenorae n. sp. was found in the kidney, renal corpuscles, renal tubules and interstitium, and had ellipsoid spores with surface ridges barely perceptible in the light microscope but clearly revealed by transmission electron microscopy. In the polysporic plasmodia, spores developed in pansporoblasts. C. reticulatum n. sp. was found in the gall bladder. It had polysporic plasmodia and spherical spores (average size 8.1 m in diameter) with a unique surface structures: elevated crests marking off irregular fields which appeared as a reticulum. In five of the fish infected with C. lenorae, bloodstream myxosporean stages of an extrasporogonic cycle were found. Further research is needed to determine whether they are stages of Sphaerospora cristata Shulman, 1962, a species also found in two of the burbot examined, or stages belonging to the Chloromyxum life cycle.     

Life Cycle of <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

Plasmodiphora brassicae is a soil-borne obligate parasite. The pathogen has three stages in its life cycle: survival in soil, root hair infection, and cortical infection. Resting spores of P. brassicae have a great ability to survive in soil. These resting spores release primary zoospores. When a zoospore reaches the surface of a root hair, it penetrates through the cell wall. This stage is termed the root hair infection stage. Inside root hairs the pathogen forms primary plasmodia. A number of nuclear divisions occur synchronously in the plasmodia, followed by cleavage into zoosporangia. Later, 4–16 secondary zoospores are formed in each zoosporangium and released into the soil. Secondary zoospores penetrate the cortical tissues of the main roots, a process called cortical infection. Inside invaded roots cells, the pathogen develops into secondary plasmodia which are associated with cellular hypertrophy, followed by gall formation in the tissues. The plasmodia finally develop into a new generation of resting spores, followed by their release back into soil as survival structures. In vitro dual cultures of P. brassicae with hairy root culture and suspension cultures have been developed to provide a way to nondestructively observe the growth of this pathogen within host cells. The development of P. brassicae in the hairy roots was similar to that found in intact plants. The observations of the cortical infection stage suggest that swelling of P. brassicae-infected cells and abnormal cell division of P. brassicae-infected and adjacent cells will induce hypertrophy and that movement of plasmodia by cytoplasmic streaming increases the number of P. brassicae-infected cells during cell division.     

Ellipsomyxa tucujuensis n. sp. (Myxozoa: Ceratomyxidae), a parasite of Satanoperca jurupari (Osteichthyes: Cichlidae) from the Brazilian Amazon

The present study describes a new coelozoic, eukaryotic microparasite of the genus Ellipsomyxa Køie, 2003 (Ceratomyxidae: Myxozoa) found parasitizing the gallbladder of Satanoperca jurupari Heckel, 1840 collected in the Curiaú River Environmental Protection Area in Macapá, Amapá state, Brazil. The fish were collected using mesh cast net. The gallbladders were examined, preserved in 80% alcohol for molecular analysis (SSU rDNA gene), and fixed in Davidson for histological slide preparation. The new parasite had a prevalence of 81% in the gallbladder, asymmetric plasmodia, irregular free spores in the bladder fluid, with no cyst formation. The spores are elliptical, with characteristics of the genus Ellipsomyxa, and they had a mean length of 10.11 (8.56–10.5) μm, mean width of 7.81 (5.96–9.56) μm, and thick walls. The polar capsules are sub-spherical in shape, slightly asymmetrical, with a mean length of 3.12 (2.31–3.99) μm and mean width of 2.5 (2.22–2.95) μm, containing polar filament with five or six coils perpendicular to the longitudinal axis of the capsule. The Bayesian Inference assigned the new species to a subclade formed by a lineage of Ellipsomyxa species from the Amazon region. Ellipsomyxa tucujuensis n. sp. is the sixth species of this genus described in fish from the Amazon region, and the first for the state of Amapá.     

Taxonomy of the genera of the Myxobolus/Myxosoma group (Myxobolidae: Myxosporea), current listing of species and revision of synonyms

A revision of the genera Myxobolus and Myxosoma is presented. On the basis of Lom & Noble (1984), all species are designated as Myxobolus. A total of 444 species of Myxobolus, including three subspecies, are listed together with their hosts. All former Myxosoma species are assigned to the genus Myxobolus and those which were previously homonyms or synonyms have been assigned new names where valid. Synonyms and other species omitted from the definitive Myxobolus list are also given.