Morphostructural data and phylogenetic relationships of a new cnidarian myxosporean infecting spleen of an economic and ecological important bryconid fish from Brazil.

A new cnidarian myxosporean infecting the spleen of an economic and ecological important bryconid fish (Salminus franciscanus) is described based on integrative taxonomic approach including morphological, ultrastructural, biological traits, geography, molecular data and phylogenetic analysis. In a total of thirty specimens examined, nineteen (63.3%) were infected by an undescribed parasite species belonging to the genus Myxobolus. Plasmodial development was asynchronous, with young development in the periphery and mature myxospores in the central area and without projections and microvilli in the plasmodial wall. Mature myxospores were ovoid in shape and measured 7.9 ± 0.2 µm (7.6-8.1 µm) in length and 5.4 ± 0.1 µm (5.0-5.6 µm) in width. The two polar capsules were equal in size, occupying a little more than half of the myxospore body, measuring 4.0 ± 0.2 µm (3.9-4.1 µm) in length and 1.7 ± 0.1 µm (1.5-1.8 µm) in width. The polar tubules coiled in six turns, perpendicular to the long axis of polar capsule. Phylogenetic analysis placed the new species within a clade containing nine myxobolid species from South American characiforms fish and appears as a close species of Myxobolus pantanalis. Nevertheless, the sequences of the new species and M. pantanalis have a large genetic divergence of 13.5% in their SSU rDNA. In light of the differences observed from the integrative taxonomy, we confidently considered that this isolate is a new species of cnidarian myxosporean, M. douradae n. sp., increasing the knowledge of diversity of this enigmatic group of cnidarians.

Morphological and molecular characterization of Ameloblastella pirarara sp. n. (Monogenoidea: Dactylogyridae) parasitizing the large Amazonian catfish Phractocephalus hemioliopterus.

In this study, integrative taxonomy is applied to describe a new dactylogyrid species, Ameloblastella pirarara sp. n. from the gills of Phractocephalus hemioliopterus, a commercially and ecologically important Amazonian catfish. Ameloblastella pirarara sp. n. can be distinguished from its congeners mainly by the morphology of the male copulatory organ (MCO), accessory piece, and anchors. The new species most resembles Ameloblastella unapi, from the Peruvian Amazon, but differs from it by the number of MCO rings, morphology of the vaginal canal and sclerotized structures of the haptor. Phylogenetic analyses based on sequences of the partial 28S rDNA (D1-D2 domains) gene placed the new species in a well-supported subclade of Ameloblastella spp. parasites of Neotropical siluriform fish, as a sister taxon to Ameloblastella unapioides. Thus, the new species described herein expands our knowledge of the diversity of monogenoid parasites from Amazonian freshwater fish.

High compliance and effective treatment of fish endoparasitic infections with oral drug delivery nanobioparticles: Safety of intestinal tissue and blood parameters.

Parasite infections in fish require constant surveillance and strategies for efficient treatments which guarantee the fish health, their sale value and the non-propagation of pathogens in new environments. Fish treatments based on nanotechnology become of increasing interest since nanoparticles have been shown as efficient materials for optimizing administration of bioactives. In this study a chitosan derivative, alginate and praziquantel conjugated nanobioparticle of effective action for oral treatment of digenetic trematodes in highly infected Corydoras schwartzi was evaluated in terms of histological and hematological safety. The inherent absence of alterations in intestinal tissue and the reversible blood cells counting during a period up to 35 days showed the safety of the drug delivery nanobioparticles, which thus represent a promising strategy for effective applications in pathogens treatments by oral administration.

Taxonomy and 18S rDNA-based phylogeny of Henneguya multiradiatus n. sp. (Cnidaria: Myxobolidae) a parasite of Brochis multiradiatus from Peruvian Amazon.

A new myxozoan species belonging to the genus Henneguya was isolated from the serous membrane of the visceral cavity of the hognosed catfish Brochis multiradiatus from Peruvian Amazon. Whitish plasmodia, macroscopically visible, were found in four of the thirty examined fishes. Mature myxospores were ellipsoidal in shape in frontal view and had a total length of 44.5 ± 0.6 µm (43.9-45.1), spore body measured 18.7 ± 0.9 µm (16.8-19.6) in length, 7.1 ± 0.2 µm (6.6-7.4) in width and 5.5 ± 0.3 µm (4.9-5.6) in thickness. The two polar capsules were elongated and equal in size, measuring 9.1 ± 0.1 µm (8.8-9.4) in length and 1.7 ± 0.1 µm (1.6-1.8) in width, occupying half of the myxospore body. Polar tubules coiled in 10-11 turns perpendicular to the long axis of the polar capsule. The caudal appendage was not bifurcated and measured 25.8 ± 0.6 µm (24.7-26.5) in length. The sequencing of the 18S rDNA gene resulted in 1400 bp and this sequence did not match any of the myxozoans available in GenBank. Phylogenetic analysis placed the new species in a well-supported subclade of Henneguya spp. infecting callichthyid fishes, with Henneguya loretoensis being the closest species. This study is the first description of a myxozoan species, Henneguya multiradiatus n. sp. from a fish of the genus Brochis.

Molecular phylogeny of the gill parasite Henneguya (Myxosporea: Myxobolidae) infecting Astyanax lacustris (Teleostei: Characidae) from fish farm in Brazil.

Molecular data of Henneguya chydadea Barassa, Cordeiro and Arana, 2003, found in the gill filaments of Astyanax lacustris bred in fish farm in the State of Mato Grosso do Sul, Brazil was obtained in order to estimate their phylogenetic position among other platysporines myxosporean. The prevalence of the parasite was 28.1% and the range intensity was 1-3 plasmodia per fish. The shape and measurements of mature myxospores were consistent with the characteristics previously defined to H. chydadea. The SSU rDNA sequence of the myxospores of H. chydadea resulted in a total of 1405 nucleotides, and this sequence did not match any of the myxozoan available in the GenBank. Phylogenetic analysis showed H. chydadea within the clade of histozoic myxosporeans and closed together with Henneguya rotunda and Myxobolus pantanalis reported in the gill arch and fins and gill filaments of Salminus brasiliensis respectively. Nonetheless, the SSU rDNA sequences of H. chydadea, H. rotunda and M. pantanalis have only 85.2% and 84.4% similarity, respectively. This is the first molecular study of a Henneguya species that parasitizes a fish belonging to the genus Astyanax in South America. The importance of myxosporeans introduction to new locations along with infected cultured host is emphasized.

Targeted Drug Delivery and Treatment of Endoparasites with Biocompatible Particles of pH-Responsive Structure.

Biomaterials conceived for vectorization of bioactives are currently considered for biomedical, biological, and environmental applications. We have produced a pH-sensitive biomaterial composed of natural source alginate and chitosan polysaccharides for application as a drug delivery system via oral administration. The composite particle preparation was in situ monitored by means of isothermal titration calorimetry. The strong interaction established between the macromolecules during particle assembly led to 0.60 alginate/chitosan effective binding sites with an intense exothermic effect and negative enthalpy variation on the order of a thousand kcal/mol. In the presence of model drugs mebendazole and ivermectin, with relatively small and large structures, respectively, mebendazole reduced the amount of chitosan monomers available to interact with alginate by 27%, which was not observed for ivermectin. Nevertheless, a state of intense negative Gibbs energy and large entropic decrease was achieved, providing evidence that formation of particles is thermodynamically driven and favored. Small-angle X-ray scattering provided further evidence of similar surface aspects independent of the presence of drug. The physical responses of the particles to pH variation comprise partial hydration, swelling, and the predominance of positive surface charge in strong acid medium, whereas ionization followed by deprotonation leads to compaction and charge reversal rather than new swelling in mild and slightly acidic mediums, respectively. In vivo performance was evaluated in the treatment of endoparasites in Corydoras fish. Systematically with a daily base oral administration, particles significantly reduced the infections over 15 days of treatment. The experiments provide evidence that utilizing particles granted and boosted the action of the antiparasitic drugs, leading to substantial reduction or elimination of infection. Hence, the pH-responsive particles represent a biomaterial with prominent characteristics that is promising for the development of targeted oral drug delivery.

Effective protection of biological membranes against photo-oxidative damage: Polymeric antioxidant forming a protecting shield over the membrane.

We have prepared a chitosan polymer modified with gallic acid in order to develop an efficient protection strategy biological membranes against photodamage. Lipid bilayers were challenged with photoinduced damage by photosensitization with methylene blue, which usually causes formation of hydroperoxides, increasing area per lipid, and afterwards allowing leakage of internal materials. The damage was delayed by a solution of gallic acid in a concentration dependent manner, but further suppressed by the polymer at very low concentrations. The membrane of giant unilamellar vesicles was covered with this modified macromolecule leading to a powerful shield against singlet oxygen and thus effectively protecting the lipid membrane from oxidative stress. The results have proven the discovery of a promising strategy for photo protection of biological membranes.

Henneguya melini n. sp. (Myxosporea: Myxobolidae), a parasite of Corydoras melini (Teleostei: Siluriformes) in the Amazon region: morphological and ultrastructural aspects.

A new species of myxozoan, Henneguya melini sp. n. (Myxosporea: Myxobolidae), was described based on morphologic and ultrastructural features. This is a parasite of the ornamental freshwater fish C. melini from the Rio Negro, and it was found in five of 30 (16.7 %) C. melini examined. The parasite was found in the gill filaments, and the plasmodia had form of round to ellipsoid, with mature and immature spores inside them. The average spore body was 15.5 ± 0.2 µm in length, 4.7 ± 0.1 µm in width, and the tail measured 25.3 ± 0.1 µm in length. The spores showed typical features of the genus Henneguya, with two valves of equal size and two symmetrical polar capsules of 4.8 ± 0.7 µm in length and 1.7 ± 0.3 µm in width. Each polar capsule had a polar filament with five to six turns. Based on morphology (morphologic and ultrastructural data) of the plasmodia and spores and the fact that this is the first report of a Henneguya species in a fish species of the genus Corydoras, it was considered a new myxozoan species.

Morphology and small subunit rDNA-based phylogeny of Ceratomyxa amazonensis n. sp. parasite of Symphysodon discus, an ornamental freshwater fish from Amazon.

The specious genus Ceratomyxa Thélodan, 1892, infect mainly gallbladder of marine fishes, with only five species reported infecting species from freshwater environment. This study performed morphological and phylogenetic analyses involving a new Ceratomyxa species (Ceratomyxa amazonensis n. sp.) found in gallbladder of Symphysodon discus Heckel, 1840 (Perciformes: Cichlidae), an important ornamental fish endemic to Amazon basin. Mature spores were strongly arcuate shaped and measured 7.0 ± 0.3 (6.2-7.6) µm in length, 15.8 ± 0.4 (15.0-16.7) µm in thickness, and polar capsules 3.22 ± 0.34 (2.4-3.6) µm in length and 2.63 ± 0.17 (2.4-2.9) µm in width. This was the first small subunit ribosomal DNA (SS rDNA) sequencing performed to Ceratomyxa species parasite of freshwater fish, and the phylogenetic analysis showed C. amazonensis n. sp. clustering in the early diverging subclade of the ceratomyxids, together with species of parasites of amphidromous/estuaries fishes, suggesting some role of the transition of the fishes between marine/freshwater environments in the evolutionary history of these parasites.

Ultrastructure and ssrRNA sequencing of Myxidium amazonense n. sp. a myxosporean parasite of Corydoras melini from the Rio Negro river, Amazonas state, Brazil.

In a survey of myxozoan parasites of ornamental freshwater fish from the Rio Negro river, it was found that seven of 30 (23.3 %) Corydoras melini specimens examined had plasmodia of a new Myxidium species (Myxidium amazonense n. sp.) in the gallbladder. The fish were caught in the Rio Negro river, in the municipality of Santa Isabel do Rio Negro, in the state of Amazonas, Brazil. The plasmodia had a tubular shape, which was organized as a spiral spring with several turns in the gallbladder. The development of the myxospores was asynchronic, with disporic pansporoblasts. Mature myxospores were elongated, with 17.0 ± 0.9 (16.1-17.9) µm in length and 3.7 ± 0.7 (3.0-4.4) µm in width, and lightly arcuate from the valval view, with their bodies tapering slowly until ending in rounded extremities. The valval surface had nine to ten grooves in each valve. The polar capsules, one at either end of the spore, had a length of 5.4 ± 0.5 (4.9-5.9) µm and a width of 3.4 ± 0.6 (2.8-4.0) µm. Ultrastructural analysis showed that the wall of the plasmodia had numerous microvilli-like structures, pinocytotic canals, and cytoplasmic bridges connecting the pansporoblasts to each other and to the ectoplasm zone. Phylogenetic analysis, based on a small subunit ribosomal RNA (ssrRNA), identified the new species as a sister species of Myxidiumceccarelli, the unique South American Myxidium species whose ssrRNA sequence is available in the NCBI database. This study is the first description of Myxidium species in ornamental freshwater fish from Amazon.

Flavonoid-Labeled Biopolymer in the Structure of Lipid Membranes to Improve the Applicability of Antioxidant Nanovesicles.

Nanovesicles produced with lipids and polymers are promising devices for drug and bioactive delivery and are of great interest in pharmaceutical applications. These nanovesicles can be engineered for improvement in bioavailability, patient compliance or to provide modified release or enhanced delivery. However, their applicability strongly depends on the safety and low immunogenicity of the components. Despite this, the use of unsaturated lipids in nanovesicles, which degrade following oxidation processes during storage and especially during the proper routes of administration in the human body, may yield toxic degradation products. In this study, we used a biopolymer (chitosan) labeled with flavonoid (catechin) as a component over a lipid bilayer for micro- and nanovesicles and characterized the structure of these vesicles in oxidation media. The purpose of this was to evaluate the in situ effect of the antioxidant in three different vesicular systems of medium, low and high membrane curvature. Liposomes and giant vesicles were produced with the phospholipids DOPC and POPC, and crystalline cubic phase with monoolein/DOPC. Concentrations of chitosan-catechin (CHCa) were included in all the vesicles and they were challenged in oxidant media. The cytotoxicity analysis using the MTT assay (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) revealed that concentrations of CHCa below 6.67 µM are non-toxic to HeLa cells. The size and zeta potential of the liposomes evidenced the degradation of their structures, which was minimized by CHCa. Similarly, the membrane of the giant vesicle, which rapidly deteriorated in oxidative solution, was protected in the presence of CHCa. The production of a lipid/CHCa composite cubic phase revealed a specific cubic topology in small-angle X-ray scattering, which was preserved in strong oxidative media. This study demonstrates the specific physicochemical characteristics introduced in the vesicular systems related to the antioxidant CHCa biopolymer, representing a platform for the improvement of composite nanovesicle applicability.

Hybrid crystalline bioparticles with nanochannels encapsulating acemannan from Aloe vera: Structure and interaction with lipid membranes.

Smart nanocarrier-based bioactive delivery systems are a current focus in nanomedicine for allowing and boosting diverse disease treatments. In this context, the design of hybrid lipid-polymer particles can provide structure-sensitive features for tailored, triggered, and stimuli-responsive devices. In this work, we introduce hybrid cubosomes that have been surface-modified with a complex of chitosan-N-arginine and alginate, making them pH-responsive. We achieved high-efficiency encapsulation of acemannan, a bioactive polysaccharide from Aloe vera, within the nanochannels of the bioparticle crystalline structure and demonstrated its controlled release under pH conditions mimicking the gastric and intestinal environments. Furthermore, an acemannan-induced phase transition from Im3m cubic symmetry to inverse hexagonal HII phase enhances the bioactive delivery by compressing the lattice spacing of the cubosome water nanochannels, facilitating the expulsion of the encapsulated solution. We also explored the bioparticle interaction with membranes of varying curvatures, revealing thermodynamically driven affinity towards high-curvature lipid membranes and inducing morphological transformations in giant unilamellar vesicles. These findings underscore the potential of these structure-responsive, membrane-active smart bioparticles for applications such as pH-triggered drug delivery platforms for the gastrointestinal tract, and as modulators and promoters of cellular internalization.

Efficient Treatment of Fish Intestinal Parasites Applying a Membrane-Penetrating Oral Drug Delivery Nanoparticle.

Nanodelivery of drugs aims to ensure drug stability in the face of adverse biochemical conditions in the course of administration, concomitant with appropriate pharmacological action provided by delivery at the targeted site. In this study, the application potential of a nanoparticle produced with biopolymers chitosan-N-arginine and alginate as an oral drug delivery material is evaluated. Both macromolecules being weak polyelectrolytes, the nanoparticle presents strong thermodynamic interactions with a biological model membrane consisting of a charged lipid liposome bilayer, leading to membrane disruption and membrane penetration of the nanoparticles in ideal conditions of pH corresponding to the oral route. The powder form of the nanoparticle was obtained by lyophilization and with a high percentage of entrapment of the anthelmintic drug praziquantel. In vivo studies were conducted with oral administration to Corydoras schwartzi fish with high intensity of intestinal parasites infection. The in vivo experiments confirmed the mucoadhesive and revealed membrane-penetrating properties of the nanoparticle by translocating the parasite cyst, which provided target drug release and reduction of over 97% of the fish intestinal parasites. Thus, it was evidenced that the nanoparticle was effective in transporting and releasing the drug to the target, providing an efficient treatment.

Interaction of polyelectrolyte-shell cubosomes with serum albumin for triggering drug release in gastrointestinal cancer.

Nano-structured and functionalized materials for encapsulation, transport, targeting and controlled release of drugs are of high interest to overcome low bioavailability in oral administration. We develop lipid-based cubosomes, which are surface-functionalized with biocompatible chitosan-N-arginine and alginate, displaying internal liquid crystalline structures. Polyelectrolyte-shell (PS) cubosomes have pH-responsive characteristics profitable for oral delivery. The obtained PScubosomes can strongly interact with serum albumin, a protein which is released in the stomach under gastric cancer conditions. An effective thermodynamic PScubosome-protein interaction was characterized at pH 2.0 and 7.4 by isothermal titration calorimetry at 37 °C. A high increment of the albumin conformation transition temperature was evidenced by differential scanning calorimetry upon incubation with PScubosomes. The performed structural studies by synchrotron small-angle X-ray scattering (SAXS) revealed essential alterations in the internal liquid crystalline topology of the nanocarriers including an Im3m to Pn3m transition and a reduction of the cubic lattice parameters. The PScubosome nanoparticle interaction with serum albumin, leading to inner structural changes in a range of temperatures, promoted the release of water from the cubosomal nanochannels. Altogether, the results revealed effective interactions of the PScubosomes with albumin under simulated gastrointestinal pH conditions and suggested promising nanocarrier characteristics for triggered oral drug release.

Discovery of a Digenean (Cryptogonimidae) Living in a Cleft-Lipped Goby, Sicyopterus cynocephalus (Teleostei: Gobiidae) from Ranongga Island, Solomon Islands: Analysis of Multiple Ribosomal DNA Regions.

This study results from a continued investigation of the occurrence and diversity of parasites of freshwater fish in the Solomon Islands. Thus, we revealed a new host as well as a new site of infection and a new geographical area for the cryptogonimid parasite, Stemmatostoma cribbi (Digenea: Cryptogonimidae). The cryptogonimid species was identified based on general morphology and on molecular data of metacercariae found in the gills of the cleft-lipped goby, Sicyopterus cynocephalus, from Ranongga Island, Western Province of the Solomon Islands. This is the first report of a Stemmatostoma sp. digenean parasitizing fish of the genus Sicyopterus in the Indo-Pacific region and the first report of S. cribbi infection in a fish from the Solomon Islands. Phylogenetic analysis performed by Bayesian inference and maximum likelihood confirmed the presence of the cryptogonimid in a well-supported subclade of Stemmatostoma spp.

Antibacterial polypeptide-bioparticle for oral administration: Powder formulation, palatability and in vivo toxicity approach.

The upsurge of bacterial resistance to conventional antibiotics turned a well-recognized public health threat. The need of developing new biomaterials of effective practical use in order to tackle bacterial resistance became urgent. In this study, a submicrometric bioparticle of known antibacterial activity was produced in powder form with suitable texture and appealing characteristics for effective oral administration. Through complex coacervating a natural-source antimicrobial polypeptide with chitosan-N-arginine and alginate, the bioactive polypeptide was physically incorporated to the bioparticle whose structure positively responds to the pH variations found in gastrointestinal tract. The powder formulation presented high palatability that was evaluated using fish as in vivo animal model. A thorough survey of the fish intestinal tissues, following a systematic oral administration, revealed high penetration potential of the biomaterial through epithelial cells and deeper intestine layers. Despite, no cytotoxic effect was observed in analyzing the tissues through different histology methods. The absence of intestinal damage was corroborated by immune histochemistry, being the integrity of epithelial motor myosin Vb and related traffic proteins preserved. Hematology further endorsed absence of toxicity in blood cells whose morphology was evaluated in detail. The study evidenced the applicability potential of a new biomaterial of appealing and safe oral administration of antibacterial polypeptide.

Occurrence of antibodies to Toxoplasma gondii and Lepstospira spp. in manatees (Trichechus inunguis) of the Brazilian Amazon.

The presence of Toxoplasma gondii and Leptospira spp. antibodies was investigated in 74 manatees (Trichechus inunguis [Mammalia: Sirenia]) kept in captivity in two rescue units in the northern region of Brazil. Antibodies to T. gondii were detected in 29 (39.2%) of 74 animals by using the modified agglutination test (titer, 1:25). For antibodies against Leptospira spp., sera were diluted 1:50 and tested against 24 strains ofleptospires by microscopic agglutination microtechnique, and positive samples were end titrated. Twenty-three (31.1%) of 74 animals were reactive to four serovars (Patoc 21/23, Castellonis 2/23, Icterohaemorrhagiae 1/23, and Butembo 1/ 23), with titers ranging from 100 to 1,600. This is the first report of antibodies against T. gondii and Leptospira spp. in T. inunguis from the Brazilian Amazon.

Cubosomal lipid nanoassemblies with pH-sensitive shells created by biopolymer complexes: A synchrotron SAXS study.

We report a strategy for sustainable development of pH-responsive cubic liquid crystalline nanoparticles (cubosomes), in which the structure-defining lyotropic nonlamellar lipid and the eventually encapsulated guest molecules can be protected by pH-sensitive polyelectrolyte shells with mucoadhesive properties. Bulk non-lamellar phases as well as pH-responsive polyelectrolyte-modified nanocarriers were formed by spontaneous assembly of the nonlamellar lipid monoolein and two biopolymers tailored in nanocomplexes with pH-dependent net charge. The mesophase particles involved positively charged N-arginine-modified chitosan (CHarg) and negatively charged alginate (ALG) chains assembled at different biopolymer concentrations and charge ratios into a series of pH-responsive complexes. The roles of Pluronic F127 as a dispersing agent and a stabilizer of the nanoscale dispersions were examined. Synchrotron small-angle X-ray scattering (SAXS) investigations were performed at several N-arginine-modified chitosan/alginate ratios (CHarg/ALG with 10, 15 and 20 wt% ALG relative to CHarg) and varying pH values mimicking the pH conditions of the gastrointestinal route. The structural parameters characterizing the inner cubic liquid crystalline organizations of the nanocarriers were determined as well as the particle sizes and stability on storage. The surface charge variations, influencing the measured zeta-potentials, evidenced the inclusion of the CHarg/ALG biopolymer complexes into the lipid nanoassemblies. The polyelectrolyte shells rendered the hybrid cubosome nanocarriers pH-sensitive and influenced the swelling of their lipid-phase core as revealed by the acquired SAXS patterns. The pH-responsiveness and the mucoadhesive features of the cubosomal lipid/polyelectrolyte nanocomplexes may be of interest for in vivo drug delivery applications.

Ultrastructure, surface topography, morphology and histological observations of a new parasitic cnidarian of the marbled swamp eel from the world's largest tropical wetland area, Pantanal, Brazil.

Myxosporeans are a diverse group of microscopic cnidarians of wide distribution that evolved into a parasitic lifestyle. A new myxosporean species, Myxobolus sp., is herein described infecting the mandible of wild specimens of Synbranchus marmoratus, caught in the world's largest tropical wetland area, Pantanal, Brazil. Light, scanning, transmission electron microscopy and histological observations unveiled detailed taxonomic information of the new myxosporean cnidarian. Ultrastructural analysis revealed a detailed description of plasmodia structures which can be used for comparison with plasmodia from other species of myxobolids. Both histological and ultrastructural observations evidenced a connective tissue capsule surrounding the plasmodia of Myxobolus sp. as a histopathological host reaction to the infection of this parasitic cnidarian. Histology showed that tissue tropism of the new myxosporean occurs in a well-defined part of the mandible, with development of plasmodia occurring in the epidermis layer. Mature myxospores from the valvular view featured an ovoid shape and had a short prolongation of the spore valves in the posterior end. Myxospores measured 22.7 ± 1.2 µm (21.5-23.9 µm) in length, 12.5 ± 0.4 µm (12.1-12.9 µm) in width and 11.3 ± 0.5 (10.8-11.8 µm) in thickness. Polar capsules were pyriform equally-sized and measuring 4.6 ± 0.3 µm (3.9-4.3 µm) in length and 2.9 ± 0.1 µm in width (2.8-3.0 µm). Finally, this study substantiates the still hidden myxosporean diversity from South America.

Host-Parasite Interaction and Phylogenetic of a New Cnidarian Myxosporean (Endocnidozoa: Myxobolidae) Infecting a Valuative Commercialized Ornamental Fish from Pantanal Wetland Biome, Brazil.

Myxozoans are a diverse group of parasitic cnidarians of wide distribution. A new species, Myxobolus matogrossoensis n. sp., is herein described infecting wild specimens of tetra mato-grosso Hyphessobrycon eques, caught in the Pantanal biome, the world's largest tropical wetland area. Cysts were found in 3 of the 30 examined fishes. Mature myxospores were ovoid in shape in frontal and measured 6.6 ± 0.4 µm (6.2-7.0 µm) in length and 3.5 ± 0.2 µm (3.3-3.7 µm) in width. The two polar capsules were elongated in shape, equal in size and occupying almost half of the myxospore body. They measured 3.3 ± 0.2 µm (3.1-3.5 µm) in length and 1.8 ± 0.1 µm (1.7-1.9 µm) in width. The polar tubules presented three to four turns. Phylogenetic analysis placed the new species within a clade containing myxobolid species from South American characiforms fish and appears as a close species of Myxobolus piraputangae and Myxobolus umidus. Nevertheless, the sequences of the new species and P. umidus and P. piraputangae have a large genetic divergence of 12 and 12.2% in their 18S rDNA gene, respectively. To the best of our knowledge, this is the first report of a Myxobolus species parasitizing the tetra fish mato-grosso, thus increasing our knowledge of cnidarian myxosporean diversity from South America.