Morphology and host–parasite interaction of Henneguya azevedoi n. sp., parasite of gills of Leporinus obtusidens from Mogi-Guaçu River, Brazil

Henneguya patriciai n. sp. (Cnidaria: Myxosporea) parasitizing Leporinus friderici (Bloch 1794) from Tartarugalzinho river, eastern Amazon

The Amazon basin has the largest number of fish in the world, and among the most common fishes of the Neotropical region, the threespot (Leporinus friderici) is cited, which in relation to its microparasitic fauna, has described only 1 species of the genus Henneguya, Henneguya friderici. The Myxozoa class is considered an obligate parasite, being morphologically characterized by spores formed by valves connected by a suture line. This study describes a new species of Henneguya sp. in the Amazon region for L. friderici. This parasite was found in the host's pyloric caeca and caudal kidney, with mature spores with a total spore length of 38.4 ± 2.5 (35.9–40.9) μm; the spore body 14.4 ± 1.1 (13.3–15.5) μm and 7.3 ± 0.6 (6.7–7.9) μm wide. Regarding its 2 polar capsules, they had a length of 5.1 ± 0.4 (4.7–5.5) μm and a width of 2.0 ± 0.1 (1.9–2.1) μm in the same pear-shaped, and each polar capsule contained 9–11 turns. Morphological and phylogenetic analyses denote that this is a new species of the genus Henneguya.

Phylogeny and ultrastructure of Henneguya fusiformis Kostoïngué, Fall, Faye and Toguebaye 1999, a newly recorded species infecting the ovaries of Clarias gariepinus in Egypt

The genus Henneguya is the second largest within the class Myxosporea, which infects marine and freshwater fish. One hundred Clarias gariepinus specimens were collected alive from a branch of the Nile River in Kafrelsheikh, Egypt. Microscopic and molecular procedures were used to describe how Henneguya fusiformis infects the ovaries of C. gariepinus. The infected fish showed no pathogenic changes except for macroscopic creamy whitish nodules in their ovaries with the highest prevalence during the spring season. The mature spores are spindle-shaped. The total spore length, spore body length and width are 53.4 ± 0.8 (52.5-54.3) µm, 29.8 ± 0.5 (29.2-30.4) µm and 6.5 ± 0.3 (6.1-6.9) µm, respectively. The spore anterior end consisted of two equal polar capsules, located in a tandem position, each one measuring 4.2 × 2.1 µm. The polar filament formed a coil with 6-8 turns. The measurement of the spore end with two extended processes was 24.3 ± 0.4 (23.9-24.8) µm. Phylogenetic analyses of the 18S ribosomal RNA gene sequence revealed that H. fusiformis are clustered together with other myxobolids that are histozoic in channel catfish, Ictalurus punctatus, and Asian Redtail catfish, Hemibagrus nemurus" (Clariidae) in the United States and Malaysia, respectively. To the best of our knowledge, this is the first record of H. fusiformis in Egypt. Additionally, our study is the first record of H. fusiformis in the ovaries of C. gariepinus.

The Amazonian fish Colossoma macropomum harbors high myxosporean diversity: A description of three novel species from a fish farm

The farming of Colossoma macropomum has intensified in recent years, leading to an increased need for research into the health of the fish. We therefore investigated the diversity of myxosporeans (Cnidaria: Myxozoa) infecting C. macropomum in a breeding system in the municipality of Rio Branco, in the state of Acre, Brazil. Twenty-four fish specimens were examined from June to August 2018. Our results revealed a high prevalence of infection, with 23 specimens (95.8%) exhibiting myxosporean plasmodia. Morphological analysis, based on light and electron microscopies, and molecular analysis (small subunit ribosomal DNA [SSU rDNA] sequencing) revealed the occurrence of three novel species of the genus Myxobolus. Plasmodia of Myxobolus guttae n. sp. were found in the fins of 75% of the specimens, and the myxospores were pear-shaped, measuring 12.3 ± 0.6 (10.3-13.5) μm in length, 8.1 ± 0.3 (7.1-8.6) μm in width, and 5.1 ± 0.6 (4.5-6.5) μm in thickness. The polar capsules were elongated and equal in size, measuring 6.8 ± 0.5 (5.8-7.6) μm in length and 2.5 ± 0.3 (1.8-3.1) μm in width, exhibiting polar tubules with 9-10 coils. The plasmodia of Myxobolus longus n. sp. were found in the gills of 45.8% of the C. macropomum specimens, and the myxospores were fusiform, measuring 16.4 ± 0.6 (14.7-17.3) μm in length, 7.1 ± 0.2 (6.8-7.7) μm in width and 5.5 ± 0.6 (4.4-6.6) μm in thickness. The polar capsules occupied more than half of the myxospore, exhibiting different sizes, the largest measuring 9.2 ± 0.5 (7.3-10.1) μm in length and 2.5 ± 0.3 (2.0-3.1) μm in width, while the smallest measured 8.5 ± 0.4 (7.1-9.1) μm in length and 2.4 ± 0.2 (1.9-3.0) μm in width. Both polar capsules contained polar tubules with 10-12 coils. For Myxobolus tambaquiensis n. sp., plasmodia were found in the opercular cavity of 41.7% of the fish specimens, and the myxospores had an oval shape, measuring 10.0 ± 0.4 (9.5-11.3) μm in length, 6.5 ± 0.2 (6.1-7.1) μm in width, and 4.6 ± 0.4 (3.9-5.6) μm in thickness. The polar capsules were elongated and equal in size, measuring 4.9 ± 0.2 (4.4-5.3) μm in length and 1.9 ± 0.2 (1.5-2.2) μm in width, closing with 8-9 coils of the polar tubule. The morphological and sequencing data of the SSU rDNA showed that the three species studied herein remain unknown to science, increasing the diversity of myxosporeans infecting C. macropomum, an iconic fish in South American freshwater fish farming. The SSU rDNA based phylogenetic analysis revealed that Myxobolus spp. parasites of C. macropomum did not have a monophyletic origin, identifying different times and pathways of the acquisition of parasites by this host species.

Morphological and molecular analysis of Henneguya tietensis n. sp. (Cnidaria: Myxosporea), parasitizing the gill filaments of Prochilodus lineatus (Valenciennes, 1837) from Brazil

The present study describes Henneguya tietensis n. sp. parasitizing Prochilodus lineatus (Valenciennes, 1837) from Brazil, through morphological and molecular analysis. Myxospores were found in the gill tissue of P. lineatus with a prevalence of 10%. The myxospores consisted of two elongate, elliptical shell valves each with a long, tapering caudal appendage. The morphology was consistent with Henneguya and the myxospore measured as follows (mean ± SD): total length 55.5 ± 2.1 μm, body length 16.2 ± 1.1 μm, body width 5.5 ± 0.1 μm, caudal appendages length 39.0 ± 2.0 μm. The polar capsules were 7.3 ± 0.2 μm long, 1.7 ± 0.2 μm wide and contained a polar filament coiled 11 to 13 turns. Histological analysis showed the plasmodia developing in the middle region of each gill filament and caused a focally extensive distension by forming a space-occupying mass within the gill filament. The ultrastructural analysis allowed the observation of the presence of mature myxospores throughout the plasmodium. Phylogenetic analysis with the SSU rDNA gene showed Henneguya tietensis n. sp. as a sister species of the subclade formed by Henneguya piaractus and Henneguya brachypomus that infect fishes of the genus Piaractus. The genetically closest species was H. piaractus, which showed a similarity of 82.4%. Using molecular and morphological characterization, the myxozoan parasite described herein represents a new species of the genus Henneguya.

Henneguya sacacaensis n. sp. (Myxozoa: Myxosporea) parasitizing gills of the acará bicudo Satanoperca jurupari (Osteichthyes: Cichlidae) in eastern Amazon

This study describes Henneguya sacacaensis n. sp. in specimens of the Osteichthyes Satanoperca jurupari (Heckel, 1840), collected in the Rio Curiaú Environmental Protection Area in the city of Macapá, state of Amapá Brazil. Using optical microscopy and molecular analysis, these cyst-shaped parasites were analyzed. The gills of 57.14% of the analyzed S. jurupari contained hundreds of spores. The cysts found on the gill lamellae were oval-shaped and whitish. The Henneguya spores had an average length of 46.5 (41.3-56.92) µm. The fusiform body of the Henneguya measured 16.5 (13.16-20.01) µm long and 5.1 (3.91-6.12) µm in width, the two polar capsules had a taper of 3.83 (3.4-4.32) µm and a width of 1.68 (1.4-1.99) µm, and the tail measured 30 (22.47-41.67) µm in length, containing a polar filament coiled seven to nine times. Morphogical and phylogenetic analysis allowed the preposition of a new species, Henneguya sacacaensis n. sp, that belongs to the family Myxobolidae and the genus Henneguya.

Henneguyosis in gills of Metynnis hypsauchen: an Amazon freshwater fish

This study describes aspects of infection caused by Myxozoa of the genus Henneguya sp. in gills of fish belonging to the species Metynnis hypsauchen. Two sampling were made in the Capim river, close to the Ribeira community, in the municipality of Ipixuna do Pará, State of Pará, Brazil, during the months of August 2018 and March 2019. The animals were captured and transported live to the Laboratório de Pesquisa Carlos Azevedo, at the Universidade Federal Rural da Amazônia (UFRA), in Belém, Pará, Brazil. The animals were examined, and after parasitism was confirmed, Differential Interference Contrast Microscopes were used, to evaluate the parasite spores. Ziehl-Neelsen stain techniques were used in histology. Necroscopic analyses of Metynnis hypsauchen specimens found parasites in 80% of the hosts (16/20), with whitish-colored cysts in the branchial filaments, containing mature spores of the genus Henneguya. The histopathological analysis indicated large areas with cystic lesions with associated ischemic necrosis. The descriptions from this study indicate that the parasite drastically compromises the host's respiratory system. Additionally, it is worth noting that parasite fauna studies of fishes in the Capim river are still a vast topic for research; this is the first record of infection by Henneguya sp. in Metynnis hypsauchen, captured in the Capim river in Ipixuna do Pará.

Molecular and morphological analysis of Henneguya jundiai n. sp. (Cnidaria: Myxosporea), a new parasite of the gills of Rhamdia quelen in Brazil

Plasmodia containing spores of a new species of myxozoan, Henneguya jundiai n. sp., were found in the gill arches of Rhamdia quelen catfish. The present study describes H. jundiai n. sp. based on morphological and molecular analysis. The mature spores were elongated and measured 26.9 ± 1.9 (22.9-29.2) μm in total spore length, 9.5 ± 0.4 (8.8-10.0) μm in spore body length, 4.6 ± 0.4 (4.1-5.5) μm in spore body width, 17.3 ± 1.8 (14.1-19.8) μm in tail length, 4.9 ± 0.3 (4.6-5.5) μm in polar capsule length and 1.4 ± 0.2 (1.2-1.7) μm in polar capsule width. The polar filaments had 6-7 coils. Histological analysis revealed the formation of a large plasmodium connected to the gill arch through the epithelial tissue. Ultrastructural analysis revealed the presence of a binucleated sporoplasm, as well as the polar capsules and the coils of the polar filament. Phylogenetic analysis found that H. jundiai n. sp. is located within a subclade formed by species of Henneguya which parasitize siluriform fish from Brazil. Henneguya jundiai n. sp. appears as a sister species of H. quelen. The results of the analyzes clearly indicated the existence of a new species, H. jundiai.

New myxosporeans parasitizing Phractocephalus hemioliopterus from Brazil: morphology, ultrastructure and SSU-rDNA sequencing

Myxozoans are a diverse group of parasitic cnidarians, with some species recognized as serious pathogens to their hosts. The present study describes 2 new myxobolid species (Myxobolus figueirae sp. nov. and Henneguya santarenensis sp. nov.) infecting skin and gill filaments of the Amazonian pimelodid fish Phractocephalus hemioliopterus, based on ultrastructural, histology and phylogenetic analysis. The fish were caught in the Amazon River, Pará, Brazil. The plasmodial development of M. figueirae sp. nov. was in the dermis and those of H. santarenensis sp. nov. were of the intralamellar type. For both species, the plasmodia were surrounded by a connective tissue layer, but there was no inflammatory infiltrate. For M. figueirae sp. nov., mature spores were ovoid measuring 9.1 to 10 (9.5 ± 0.3) µm in length, 5.8 to 6.9 (6.4 ± 0.3) µm in width and 4.4 to 4.5 (4.5 ± 0.1) µm in thickness. Two polar capsules were elongated and of unequal size. For H. santarenensis sp. nov., mature spores were ellipsoidal in the frontal view, measuring 26.3 to 36.1 (31.9 ± 3) µm in total length, 9.6 to 11.9 (10.8 ± 0.5) µm in body length, 3.7 to 4.9 (4.3 ± 0.3) µm in width and 16.6 to 25.6 (21 ± 3.1) µm in caudal process. The polar capsules were elongated and of equal size. Phylogenetic analysis, based on partial small subunit ribosomal DNA (SSU rDNA) sequences and using the closest myxozoan sequences to each one of the species studied here based on previous GenBank data, showed M. figueirae sp. nov. and H. santarenensis sp. nov. clustering in distinct lineages. While H. santarenensis sp. nov. clustered in a well-supported subclade composed of Henneguya species that infect gills of South American pimelodid hosts, M. figueirae sp. nov. clustered in a weakly supported subclade containing parasite species of bryconid hosts.

New morphological data and molecular diagnostic of Henneguya friderici (Myxozoa: Myxobolidae), a parasite of Leporinus friderici (Osteichthyes: Anostomidae) from southeastern Brazil

The myxozoan Henneguya friderici is a parasite of the gills, intestine, kidney and liver of Leporinus friderici, a characiform fish belonging to the family Anostomidae. Forty-two specimens of L. friderici that had been caught in the Mogi Guaçú River, state of São Paulo, were studied. Elongated white plasmodia were found in the gill filaments of 10 host specimens (24%). The mature spores had an ellipsoidal body with polar capsules of equal size and caudal length greater than body length. This study also described 18S rDNA sequencing of H. friderici infecting the gill filaments. This produced a sequence of 1050 bp that demonstrated significant genetic differences with previously described species of Henneguya. Similarity analysis using sequences from species that clustered closest to those produced by this study showed that the species with greatest genetic similarity to H. friderici was H. leporinicola, with 94% similarity.

Small subunit ribosomal RNA sequence links the myxospore stage of Henneguya mississippiensis n. sp. from channel catfish Ictalurus punctatus to an actinospore released by the benthic oligochaete Dero digitata

There are more than 200 species of Henneguya described from fish. Of these, only three life cycles have been determined, identifying the actinospore and myxospore stages from their respective hosts. Two of these life cycles involve the channel catfish (Ictalurus punctatus) and the freshwater oligochaete Dero digitata. Herein, we molecularly confirm the life cycle of a previously undescribed Henneguya sp. by matching 18S ribosomal RNA (rRNA) gene sequence of the myxospore stage from channel catfish with the previously described actinospore stage (Aurantiactinomyxon mississippiensis) from D. digitata. Gill tissue from naturally infected channel catfish contained pseudocysts restricted to the apical end of the primary lamellae. Myxospores were morphologically consistent with Henneguya spp. from ictalurid fishes in North America. The spores measured 48.8 ± 4.8 μm (range = 40.7-61.6 μm) in total spore length. The lanceolate spore body was 17.1 ± 1.0 μm (14.4-19.3 μm) in length and 5.0 ± 0.3 μm (4.5-5.5 μm) in width. The two polar capsules were 6.2 ± 0.4 μm (5.8-7.0 μm) long and 5.0 ± 0.3 μm (4.5-5.5 μm) wide. The polar capsule contained eight to nine coils in the polar filament. The two caudal processes were of equal length, measuring 31.0 ± 4.1 μm (22.9-40.6 μm). The 1980-bp 18S rRNA gene sequence obtained from two excised cysts shared 99.4% similarity (100% coverage) to the published sequence of A. mississippiensis, an actinospore previously described from D. digitata. The sequence similarity between the myxospore from channel catfish and actinospore from D. digitata suggests that they are conspecific, representing alternate life stages of Henneguya mississippiensis n. sp.

Histopathological and ultrastructural studies of a Henneguya species (Myxozoa: Myxosporea) infesting the intestine of Clarias gariepinus from Benin (West Africa)

Fish culture is the best alternative to fill the gap between natural fish catches and estimated needs of populations in animal protein consumption. In West Africa, this goal required to have suitable fishes for aquaculture which are Clariidae and Tilapia. Clarias gariepinus (Clariidae) fetches a higher price than tilapias as it can be sold alive at the market but a high infestation by Henneguya leads to decrease this commercial value. Those reasons lead us to perform studies on seasonal variations, histopathological aspects and life cycle of Henneguya sp. infecting the intestine of C. gariepinus using light and electron microscope. From November 2011 to December 2012, 339 specimens were collected from Ouémé River (Benin) and examined. An overall prevalence of 7.37 % was recorded for plasmodia of Henneguya sp. Parasite occurrence did not vary significantly between seasons (χ(2) = 12.235; df = 3; p > 0.05), nor sexes (χ(2) = 2.992; df = 7; p > 0.05) while differences were significant between classes of weight (χ(2) = 39.929; df = 5; p < 0.05). The highest prevalence was recorded in host ranging from 300 to 374 g. Histopathological analysis showed that the mass continuous development of the plasmodium produced thickening of the intestine wall and compressed neighboring tissues and destroyed villi and smooth muscle layers. The stages of the parasite development including sporogenesis, capsulogenesis, and valvogenesis were asynchronous. Investigations are still running by molecular approaches in order to identify accurately this species.

Ultrastructure and phylogeny of the parasite Henneguya carolina sp. nov. (Myxozoa), from the marine fish Trachinotus carolinus in Brazil

Microscopic and molecular procedures are used to describe a new myxosporean species, Henneguya carolina sp. nov., found infecting the intestine of the marine teleost fish Trachinotus carolinus on the southern Atlantic coast of Brazil. Spherical to ellipsoid cysts, measuring up to ~750 µm, display synchronous development. Mature myxospores are ellipsoidal with a bifurcated caudal process. Myxospore body length, width, and thickness are 12.7 ± 0.8 (12.0-13.4) µm, 8.8 ± 0.6 (7.5-9.6) µm, and 5.8 ± 0.4 (5.0-6.4) µm, respectively; 2 equal caudal processes are 16.8 ± 1.1 (15.9-18.0) µm long, and the total myxospore length is 29.4 ± 0.8 (28.4-30.4) µm. Two pyriform polar capsules measure 5.0 ± 0.5 (4.6-5.6) × 2.4 ± 0.4 (1.9-2.9) µm, and each contains a polar filament forming 3 to 4 coils. Sporoplasm is binucleated and presents a spherical vacuole surrounded by numerous globular sporoplasmosomes. Molecular analysis of the small subunit rRNA gene by maximum parsimony, neighbor joining, and maximum likelihood reveals the parasite clustering together with other myxobolids that are histozoic in marine fish of the order Perciformes, thereby strengthening the contention that the host phylogenetic relationships and aquatic environment are the strongest evolutionary signal for myxosporeans of the family Myxobolidae.

Henneguya cuniculator sp. nov., a parasite of spotted sorubim Pseudoplatystoma corruscans in the São Francisco Basin, Brazil

Henneguya cuniculator sp. nov. was found infecting spotted sorubim catfish Pseudoplatystoma corruscans from the São Francisco River, Minas Gerais, Brazil. The parasites form elongated plasmodia of up to 1 cm in length in the gill filaments. Mature spores were ellipsoidal from the frontal view, with total length of 29.4 ± 2.4 (mean ± SD, range 23.3-32.4) µm, body length of 12.1 ± 1.0 (10.0-14.7) µm, width of 4.8 ± 0.4 (4.0-5.9) µm, and tail length of 16.7 ± 2.0 (12.3-19.4) µm. From the lateral view, spores were biconvex, with thickness of 4.2 ± 0.7 (3.9-4.9) µm. The polar capsules were elongated and equal in size, 6.2 ± 0.3 (5.2-6.2) µm in length, and 1.8 ± 0.1 (1.4-1.9) µm in width. Ultrastructural analysis showed that the plasmodial wall had delicate projections towards the host tissue and a thin layer that prevented contact between the host cells and the parasite. In the ectoplasm, few mitochondria were observed, while generative cells, early stages of sporogenesis, and advanced spore development occurred in the plasmodial periphery, and more mature spores in internal regions. Histopathological analysis showed that plasmodia developed in the sub-epithelial connective tissue of gill filaments, causing compression of the adjacent tissues, deformation of gill filaments, and lamellar fusion. Phylogenetic analysis, based on 18S rDNA genes and using only Henneguya/Myxobolus species parasites of siluriform fish, showed grouping according to the fish family.

Henneguya mauritaniensis n. sp. (Myxozoa) from the arterial bulb of Pagrus caeruleostictus (Valenciennes, 1830) off Mauritania

We describe a new species of myxozoan, Henneguya mauritaniensis n. sp., extracted from the arterial bulb of the bluespotted seabream, Pagrus caeruleostictus (Valenciennes, 1830), collected in Mauritanian waters. Out of the 209 individuals examined, 30.1 % were infected with this new taxon. Spore total length ranged from 15.0 to 20.5 μm with a mean of 17.9 μm. The two polar capsules were equal in size, and pyriform and caudal appendages joined until mid-length. Morphometric analysis revealed significant differences between H. mauritaniensis n. sp. and morphologically similar species from this region as well as congeners known from other sparid hosts. Phylogenetic analysis of 18 S rDNA indicated that this new species is closely related to Henneguya pagri, reported recently from Pagrus major off Japan. Bayesian inference and maximum likelihood analyses of the 18 S rDNA dataset also revealed that species of marine Henneguya reported forming pseudocysts in the hearts of their fish hosts were closely related. Histological analysis of the H. mauritaniensis n. sp. pseudocysts embedded in the arterial bulb of P. caeruleostictus suggests that these parasites may cause considerable pathology, which may impact negatively on the health of the fish host. Finally, we discussed the importance of a combination of morphological and molecular analysis for species description because of high variability in size within the same taxa.

Three novel myxobolid species of genera Henneguya and Myxobolus (Myxosporea: Bivalvulida) from marine fish in Japan

Myxosporean genera Henneguya and Myxobolus (Bivalvulida: Myxobolidae) are closely related in morphology and molecular phylogeny, speciose with approximately 1,000 nominal species. The majority of them are recorded from freshwater fish worldwide, and few are known from marine fish. In this study, three myxobolid spp. are described from marine fish around Japan. Two novel Henneguya spp., Henneguya ogawai sp. n. and Henneguya yokoyamai sp. n., are described from two black sea breams (Acanthopagrus schlegelii) fished in the Inland Sea (Setonaikai), Japan. Plasmodia of the former species were localized in the esophageal or intestinal wall, and those of the latter species were in the wall of the gall bladder and peritoneum. Spore development in plasmodia of these two species was synchronous. The spore body of H. ogawai sp. n. was 11.0 (8.9-12.2) μm in length, 6.9 (6.3-7.5) μm in width, 5.9 (5.2-6.6) μm in thickness, with a bifurcated caudal process of equal length, 10.0 (8.4-12.7) μm long; total spore length, 21.1 (19.2-23.4) μm. It contained two polar capsule, 4.3 (3.8-5.2) × 1.9 (1.4-2.3) μm. The spore body of H. yokoyamai sp. n. was 11.0 (10.1-13.7) μm in length, 7.1 (6.6-7.5) μm in width, and 5.6 (4.5-6.4) μm in thickness, with a bifurcated caudal process of equal length, 14.1 (10.8-17.0) μm long; total spore length, 25.0 (21.9-29.2) μm. It contained two polar capsules, 3.7 (3.1-4.2) × 2.0 (1.8-2.4) μm. A novel Myxobolus sp., Myxobolus machidai sp. n., is described from a spotted knifejaw (Oplegnathus punctatus) fished in the Sea of Japan, off Shimonoseki, Yamaguchi Prefecture, Japan. Plasmodia were embedded in the esophageal wall. Its round spore was small in size, 9.0 (8.1-9.4) μm in length, 7.8 (7.5-8.3) μm in width, and 5.5 (5.1-6.0) μm in thickness. It contained two polar capsules, 3.5 (3.2-3.8) × 2.3 (2.2-2.5) μm. Spore development in a plasmodium was asynchronous. Nucleotide sequencing of the small subunit ribosomal RNA gene (SSU rDNA) of these two novel Henneguya spp. revealed a close phylogenetic relationship with the marine clade of Henneguya spp.; however, they were distinct in morphology and SSU rDNA sequence from any known species. M. machidai sp. n. was grouped with freshwater Henneguya spp. in a phylogenetic tree based on the SSU rDNA, distant from a known marine clade of Myxobolus spp. reported mainly from the Mediterranean Sea. This is the first record of Henneguya-Myxobolus spp. from natural marine water in Japan.