Three Unicapsula species (Myxosporea: Trilosporidae) of Asian marine fishes, including the description of Unicapsula setoensis n. sp. in the yellowfin goby (Acanthogobius flavimanus) from the Inland Sea of Japan.

Kudoa neothunni is the first described Kudoa species having six shell valves and polar capsules, previously assigned to the genus Hexacapsula Arai and Matsumoto, 1953. Since its genetic analyses remain to be conducted, the present study characterizes the ribosomal RNA gene (rDNA) using two isolates from a yellowfin tuna (Thunnus albacares) with post-harvest myoliquefaction and a northern bluefin tuna (Thunnus thynnus) without tissue degradation. Spores of the two isolates localized in the myofiber of trunk muscles, forming pseudocysts, and showed typical morphology of K. neothunni with six equal-sized shell valves radially arranged in apical view: spores (n = 15) measuring 9.5-11.4μm in width, 7.3-8.6μm in suture width, 8.9-10.9μm in thickness, and 7.3-7.7μm in length; and polar capsules measuring 3.6-4.1μm by 1.8-2.3μm. In lateral view, the spores were pyramidal in shape without apical protrusions. Their 18S and 5.8S rDNA sequences were essentially identical, but variations in the ITS1 (62.4% similarity across 757-bp length), ITS2 (66.9% similarity across 599-bp length), and 28S (99.0% similarity across 2,245-bp length) rDNA regions existed between the two isolates. On phylogenetic trees based on the 18S or 28S rDNA sequence, K. neothunni formed a clade with Kudoa spp. with more than four shell valves and polar capsules, particularly K. grammatorcyni and K. scomberomori. Semiquadrate spores of a kudoid species with four shell valves and polar capsules were detected from minute cysts (0.30-0.75mm by 0.20-0.40mm) embedded in the trunk muscle of a chub mackerel (Scomber japonicus) fished in the Sea of Japan. Morphologically, it resembled K. caudata described from a chub mackerel fished in the southeastern Pacific Ocean off Peru; however, it lacked filamentous projections on the shell valves of spores. Additionally, it morphologically resembled K. thunni described from a yellowfin tuna also fished in the Pacific Ocean; spores (n = 30) measuring 8.2-10.5μm in width, 7.0-8.8μm in thickness, and 6.1-6.8μm in length; and polar capsule measuring 2.5-3.4μm by 1.3-2.0μm. The similarities of the 18S and 28S rDNA sequences between these two species were 98.5% and 96.3%, respectively. Simultaneously, the dimensions of cysts in the trunk muscle formed by K. thunni are clearly larger than those of the present species from a chub mackerel: 1.3-2.0mm by 1.1-1.4mm (n = 14) vs. 0.30-0.75mm by 0.20-0.40mm (n = 7), respectively. Thus, Kudoa scomberi n. sp. is proposed for this multivalvulid species found in the chub mackerel.

Henneguya azevedoi n. sp. is described from the piava (Leporinus obtusidens). Between 2005 and 2007, 60 fish were collected from the Mogi-Guaçu River near Cachoeira de Emas Falls located in the municipality of Pirassununga, state of São Paulo, Brazil. A total of 70% had plasmodia of the parasite. The plasmodia were white, spherical, and measured 40-200 μm in diameter. Histopathological analysis revealed that the development of the parasite was intralamellar and caused stretching of the epithelium, with accentuated deformation, as well as compression of the capillary and adjacent tissues. Ultrastructural analysis revealed that the wall of the plasmodium was a single membrane in direct contact with the host cells and contained pinocytic canals that extended into the plasmodium. The development of the parasite was asynchronous, with the earliest stages at the periphery and mature spores in the central region. Mature spores were elongated in the frontal view [mean ± standard deviation (range)]: 45.2 ± 0.6 (45.0-47.0) μm in total length, 10.0 ± 0.07 (9.9-10.2) μm in body length, 35.6 ± 0.9 (34.9-36.5) μm in caudal process length, and 4.4 ± 0.4 (4.0-5.0) μm in body width. The polar capsules were elongated and equal in size: 3.8 ± 0.3 (3.5-4.0) μm in length and 1.0 μm in width. The polar filaments were coiled in six to seven turns and perpendicular to the axis of the capsule. Scanning electron microscopy revealed smooth valves and a conspicuous rim around the spore body. This is the first time that a myxosporean has been reported in L. obtusidens.

Myxobolus gutturocola n. sp. was isolated from the throat of silver carp, Hypophthalmichthys molitrix, in Chongqing, China. Myxospore valves are unsymmetrical and smooth. Mature spores are ellipsoidal in frontal view, measuring 12.5 ± 0.2μm (n = 25) in length, 8.4 ± 0.2μm (n = 25) in width and 7.1 ± 0.2μm (n = 25) in thickness. Each spore has two pyriform and unequal sizes polar capsules, the large one with 5.7 ± 0.2μm in length × 3.6 ± 0.2μm in width and the small one with 4.6 ± 0.2μm in length × 2.6 ± 0.1μm in width. Polar filaments are coiled seven or eight turns in the large polar capsule and four or five turns in the small polar capsule. The coils are arranged almost perpendicularly to the longitudinal axis of the polar capsule. Morphological analysis revealed that M. gutturocola n. sp. is distinct from related species of Myxobolus Bütschli, 1882. Molecular analysis has demonstrated that its SSU rDNA sequences do not match with any available sequences in GenBank. Phylogenetic analysis of the SSU rDNA sequences indicated this species clustered in a clade composed exclusively of parasites infecting the fishes of the Leucisini lineage and most closely related to Myxobolus pavlovskii isolated from the gill filaments of silver carp in Hungary.

Henneguya ovata n. sp. (Myxosporea: Bivalvulida), causing severe enteric henneguyosis of net-cage-cultured ovate pompano, Trachinotus ovatus in China

Taxonomy, phylogeny and host-parasite interaction of two novel Myxobolus species infecting Brycon orthotaenia from the São Francisco River, Brazil

Host–parasite–environment relationship, morphology and molecular analyses of Henneguya eirasi n. sp. parasite of two wild Pseudoplatystoma spp. in Pantanal Wetland, Brazil

Ortholinea scatophagi (Myxosporea: Ortholineidae), a novel myxosporean infecting the spotted scat, Scatophagus argus (Linnaeus 1766) from southwest coast of India

The resolution of the taxonomic dilemma of Myxobolus colossomatis and description of two novel myxosporeans species of Colossoma macropomum from Amazon basin

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

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.

Skin nodules associated with parasitism with Henneguya sp. (Cnidaria: Myxosporea) in the neotropical fish Cyphocharax modestus

A new Myxobolus species, Myxobolus mucosus sp. n., was found in the basifilamental location of roach, Rutilus rutilus, and common dace, Leuciscus leuciscus, during the investigation of fish myxosporean fauna in Finnish Bay of Baltic Sea and Lake Ladoga in 2014. Plasmodia from the two hosts share similar morphometric and morphological features which are whitish and slightly elongated oval and measured 300-500 μm in diameter. Mature spores of M. mucosus sp. n. are ellipsoidal in frontal view and lemon shaped in sutural view, measuring 13.6 ± 0.62 (12.8-14.2) μm in length, 10.7 ± 0.51 (10.3-11.4) μm in width, 7.8 ± 0.41 (7.2-8.3) μm in thickness and 13.0 ± 0.89 (11.5-14.2) μm in length, 10.8 ± 0.77 (10.2-11.5) μm in width, 7.7 ± 0.52 (7.3-8.0) μm in thickness from roach and common dace, respectively. Polar capsules were pyriform, equal in size, converging anteriorly, with 5.9 ± 0.22 (5.7-6.3) μm in length and 3.9 ± 0.3 (3.5-4.1) μm in width and 5.6 ± 0.38 (5.1-6.2) μm in length and 3.8 ± 0.24 (3.5-4.0) μm in width from roach and common dace, respectively. Spore valves are relatively thin, symmetrical, and smooth. The most remarkable morphological character of this new Myxobolus species is the distinct mucous envelope, surrounding the full myxospore valves, up to 25 and 32 μm, respectively, in roach and common dace. The partial 18S ribosomal DNA (rDNA) sequence variation of myxospores from two hosts is very tiny (below 0.8 %) but significantly differing from all available sequences of myxosporeans in GenBank. Therefore, it can be concluded that this myxosporean from these two closely related cyprinids are conspecific by combining morphological characteristics, tissue specificity, and molecular data. Phylogenetic analysis showed that this newly described species cluster with several gill-infecting Myxobolus species from cyprinid fish inhabiting in Eastern Europe.

In the present study, we described a novel myxosporean species, Myxobolus jialingensis n. sp. (Myxozoa: Myxobolidae), which infected the urinary bladder and hepatopancreas of yellowhead catfish Tachysurus fulvidraco in China. The mature spores of M. jialingensis n. sp. were pyriform with the length of 15.8 ± 0.7 (15.4-17.0) μm and width of 8.0 ± 0.3 (7.8-8.9) μm. Two pyriform polar capsules were slightly unequal in size: the larger polar capsule was 7.4 ± 0.3 (6.7-8.0) μm in length and 3.1 ± 0.2 (2.8-3.6) μm in width; and the smaller polar capsule measured 7.3 ± 0.3 (6.6-8.1) μm in length and 3.3 ± 0.2 (2.9-3.6) μm in width. The polar capsules were directed toward the apex of the spore, packing seven to eight spirals of the polar filaments. The small subunit ribosomal RNA gene (18S rDNA) sequence of M. jialingensis n. sp. was unique among all myxozoans, and the highest similarity was 96.1% with M. voremkhai. Phylogenetic analysis based on 18S rDNA sequences revealed that myxosporeans infecting the close host affinity (belonging to the same order) had close phylogenetic relationship and, some myxosporeans infecting the same host order might have multiple origins.

Myxidium kudoi Meglitsch, 1937 has been described from the type host, blue catfish Ictalurus furcatus, with no additional host records or molecular data available for this species. To provide molecular data and a novel host locality for this species and carry out phylogenetic analyses to infer the evolutionary relationship of the species to other members of the family Myxidiidae for which DNA sequence data is available. These data were collected using myxospores from the gallbladder of a blue catfish, Ictalurus furcatus collected from Lake Texoma, Oklahoma, USA. Myxospores were morphologically consistent with the only other account of this species and not any other Myxidium species described from siluriform fishes. Myxospores were oblong with rounded ends and were 10.8-12.6 (11.6 ± 0.5) µm in length and 4.7-6.6 (5.7 ± 0.5) µm in width. Polar capsules were subspherical and 2.7-3.9 (3.4 ± 0.3) µm in length and 2.4-3.5 (3.1 ± 0.3) µm in diameter, with each capsule containing a polar filament with 3-4 coils. Molecular data consisted of a 2918-bp sequence of the partial 18S, complete ITS1, 5.8S, ITS2, and partial 28S ribosomal rRNA regions as well as a 2455-bp sequence of partial 28S ribosomal RNA. The partial 18S and 28S data was used in a concatenated Bayesian phylogenetic analysis to further infer the evolutionary relationships of the Myxidiidae. Additionally, the partial 18S data was used in a separate phylogenetic analysis. The present work reports novel morphological and molecular data for Myxidium kudoi as well as a novel locality of occurrence for this species. In concatenated phylogenetic analysis using 18S and 28S data and other molecular data from Myxozoa, M. kudoi grouped with other freshwater Myxidiidae. In the single-locus, 18S analysis, M. kudoi grouped with Myxidium rhodei from Rutilus rutilus and Myxidium amazonense from Corydoras melini, the only other Myxidium species of catfish for which molecular data are available.

The present study records the presence of Bipteria lusitanica n. sp. in wild white seabream, Diplodus sargus (Linnaeus, 1758) off the Portuguese coast. Myxosporean parasites were found in the interstitial tissue of kidney and free in urinary bladder of D. sargus with a 33.3% of prevalence of infection. Myxospores were triangular or inversely pyramidal in shape and anteriorly wider in frontal view, measuring 11.2 ± 1.0μm in length, 12.6 ± 0.9μm in width, and 11.6 ± 0.4 μm in thickness. The sinuous sutural line was parallel to the axis that connects the center of the two polar capsules. Spore valves were smooth without ridges. Wing-like appendages extended from the posterior part of each valve in sutural view, measuring 3.9 ± 1.1μm in length. Spherical polar capsules measured 4.4 ± 0.2μm in diameter and the polar filaments were helical arranged in 5-6 turns. Molecular data showed that this parasite clusters within species of the Sinuolineidae Shulman, 1959 family, and they all infect the urinary bladder. Using molecular and morphological characterization, we were able to identify this parasite as a novel species of the genus Bipteria Kovaleva, Zubtchenko, and Krasin, 1983.