Multiple evolutionary routes of the single polar capsule in Thelohanellus species (Myxozoa; Myxobolidae)

Henneguya (Cnidaria: Myxobolidae) species infecting Oligosarcus jenynsii (Characiformes: Characidae) in a Neotropical shallow lake from Argentina: morphological and molecular characterisation

Two previously undescribed myxozoan species, Henneguya sardellae sp. n. and H. margaritae sp. n., found infecting connective tissues of the Neotropical characid fish Oligosarcus jenynsii (Günther) from Argentina are morphologically and molecularly characterised. Mature spores of H. sardellae sp. n. are ellipsoid, with two, straight and visibly fused caudal appendages cleaved at its blunt terminal end; measuring 33.5 ± 1.2 (30.9-35.5) μm in total length, spore body 17.5 ± 0.6 (16.3-18.6) µm, 7.8 ± 0.4 (7.0-8.8) µm wide and 6.9 ± 0.2 (6.6-7.2) µm thick, with two elongated, unequally-sized polar capsules situated at anterior end, and 11-13 turns of polar tubules. Mature spores of H. margaritae sp. n. are pyriform, with two caudal appendages visible fused together and much longer than spore body, with unequal endings; measuring 35.9 ± 2.8 (29.2-40.7) µm in total length, spore body 11.5 ± 0.9 (9.2-13.0) µm long, 5.8 ± 0.4 (5.1-6.7) µm wide and 5.5 ± 0.2 (5.1-5.8) µm thick, with two polar capsules similar in size, pyriform polar capsules containing polar tubules with 4-5 coils. Both species showed a membraneous sheath surrounding the spore body and caudal appendages; in H. sardellae sp. n. this feature can deploy laterally. Phylogenetic analyses based on SSU rDNA sequences showed that H. sardellae sp. n. and H. margaritae sp. n. clustered with other myxobolids parasitising Characiformes in Brazil, Cichliformes in Mexico and Cyprinodontiformes in Mexico and the United States. The description of these two new species of Henneguya as the first described species of the genus that parasitise freshwater fish in Argentina highlights the importance of further research on the diversity and distribution of myxozoans in this region.

A NEW SPECIES OF THELOHANELLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE GILL OF QUILLBACK, CARPIODES CYPRINUS (CYPRINIFORMES: CATOSTOMIDAE), FROM THE ARKANSAS RIVER DRAINAGE OF OKLAHOMA

During May 2022 and again in March 2023, 5 quillbacks, Carpiodes cyprinus, were collected from the Verdigris River, Wagoner County, Oklahoma (n = 1), and the Black River, Lawrence County, Arkansas (n = 4), and their gill, gallbladder, fins, integument, musculature, and other major organs were macroscopically examined for myxozoans. Gill lamellae from the single quillback from the Verdigris River was infected with a new myxozoan, Thelohanellus oklahomaensis n. sp. Qualitative and quantitative morphological data were obtained from fresh and formalin-fixed preserved myxospores, and molecular data consisted of a 1,767 base pair sequence of the partial small subunit (SSU) ribosomal RNA gene. Phylogenetic analysis grouped T. oklahomaensis n. sp. with myxozoans known to infect North American catostomids and Eurasian cyprinids. Histological examination localized plasmodia to an intralamellar developmental site and revealed a possible vestige of a second polar capsule. Although plasmodia markedly expanded lamellae, there were no associated epithelial or inflammatory changes. Thelohanellus oklahomaensis n. sp. is the only member of the genus known to infect the gills of C. cyprinus.

Morphological, histological and phylogenetic identification of three species of Myxobolus (Myxosporea: Myxobolidae) infecting different carp lineages in China

The global cultivation of common carp Cyprinus carpio is developed primarily for either food or recreational purposes and myxosporean infections causing significant economic losses are regularly troublesome for carp farmers. However, most myxosporean species are poorly characterized, making it difficult to correctly elaborate on their parasitism mode and determine pathogenicity. Here, based on an integrative approach, we supplemented fundamental information on three Myxobolus species infecting different carp lineages in China. Myxobolus elliptoides Wu et Chen, 1987; Nine new species of Myxosporida from freshwater fish of Wuhu lake, Hubei, China. Acta Hydrobiologica Sinica, 11, 161 formed yellowish pseudocysts in the anal fin of common carp and were observed with ellipsoidal myxospores and two polar capsules of distinct dimensions. The dermal tissue within the fin ray was regarded as the type site for growing plasmodia of M. elliptoides. Myxobolus basilamellaris Lom et Molnar, 1983; Myxobolus basilamellaris sp. n. (myxozoa, Myxosporea), a parasite of the gills of common carp (Cyprinus carpio L.). Folia Parasitologica, 30, 1 aggregated ellipsoidal myxospores at the base of the gill filaments of koi carp juvenile, causing significant tissue damage. Myxobolus artus Achmerov, 1960, enwrapped in diffuse pseudocysts, was observed throughout the trunk muscle of mirror carp. Its oblate myxospores were asymmetrical and contained two unequal-sized polar capsules. According to the localization of large plasmodia, inter- and intramuscular preferences were displayed by M. artus. For precise species identification, we provided the SSU rDNA sequences for each species of Myxobolus. Among them, M. elliptoides was molecularly characterized for the first time, showing the highest 94.21% identity to Thelohanellus sinensis (KY469292). Phylogenetically, the affinity of both M. artus and M. basilamellaris to their conspecific species derived from different carp lineages was highly supported. Moreover, the intermixed cluster of Myxobolus species, including M. elliptoides, with those of Thelohanellus species provided evidence for querying the monophyletic evolution history of these taxa. This work updates the appreciation of the concerned species and enhances our understanding of the parasite fauna of common carp.

Myxobolus shuifuensis sp. n. (Myxozoa: Myxobolidae) infecting the exotic mrigal Cirrhinus mrigala feral in China

Myxobolus species represents a group of cosmopolitan metazoan parasites commonly harbored in the farmed and wild fish populations. Here, a species of Myxobolus is found in the kidney of an exotic mrigal Cirrhinus mrigala feral in the Yangtze River and utilized for an integrative characterization. Ellipsoidal myxospores are measured at 15.68 ± 0.8 (13.93-17.11) × 11.42 ± 0.54 (10.34-12.3) × 7.94 ± 0.35 (7.58-8.5) μm in dimension. The polar capsules are pyriform, and unequal in size. The morphological and morphometric characteristics of the present isolates are distinct from those of other congeners. Molecularly, the pairwise comparison based on the SSU rDNA sequence indicates that the present amplicon does not match any sequences available in the GenBank database and shares the highest similarity of 92.12% to Myxobolus pavlovskii (MG520369). Accordingly, we propose a name Myxobolus shuifuensis sp. n. for the present isolates. Phylogenetical trees indicate an apparent host-associated phylogenetic pattern. M. shuifuensis sp. n. groups loosely with other Myxobolus species isolated from Cirrhinus fish. Insead, it forms a sister clade to some myxosporeans belonging to the Thelohanellus genus. This result underpins the species identification and provides evidence for challenging the taxonomic separation among both morphologically comparable genera.

Diversity of myxozoans parasitizing the catfish Rhamdia quelen (Siluriformes: Heptapteridae), in southeastern Brazil, based on morphological and molecular evidence

Rhamdia quelen is a commercially important fish in South America. During the survey of myxozoan infections in fishes from Pardo River, Paranapanema River basin, São Paulo State, Brazil, we describe three new species of Henneguya found parasitizing gills of R. quelen: Henneguya bagre n. sp., Henneguya breviscauda n. sp and Henneguya novaerae n. sp. The descriptions were based on myxospores morphology and small subunit ribosomal DNA partial sequences. Phylogenetic analysis showed a clade formed by species that parasitize Siluriformes, with Henneguya jundiai as a sister species of Henneguya bagre n. sp., Henneguya breviscauda n. sp and Henneguya novaerae n. sp. Our study indicates that the parasites infecting R. quelen belong to a lineage of myxozoans infecting Heptapteridae fishes. Using molecular and morphological characterization, the species were identified as new species for the genus Henneguya. Based on our analysis we recommend monitoring the presence of these parasites in farmed fishes, to analyze possible pathologies caused by them.

Morphological and molecular studies on two myxosporean infections of cyprinid fishes: Thelohanellus pyriformis from tench and Thelohanellus cf. fuhrmanni from nase

During surveys on myxosporean parasites of Lake Balaton and River Danube fishes, two Thelohanellus spp. were found on tench (Tinca tinca) and on common nase (Chondrostoma nasus). They were identified as Thelohanellus pyriformis and Thelohanellus cf. fuhrmanni, respectively. Myxospores of T. pyriformis from tench were collected from arteria branchialis afferens of gill filaments. The mature myxospores of this species were pyriform in shape and 19 ± 0.6l (18–19.5) long, 8.2 ± 0.54 (7.5–9) wide, 7.3 ± 0.25 (7–7.5) thick containing polar tubules with 9–10 turns. The plasmodia of Thelohanellus cf. fuhrmanni were collected from under the skin of snout of the common nase. The myxospores were pyriform, 16.3 ± 0.39l (15.5–16.5) long, 6.5 ± 0.55 (6.3–7) wide, 6.3 ± 0.53 (5.8–7) thick containing polar tubules with 6 turns. Small subunit ribosomal DNA sequences of both Thelohanellus species differed from other known myxozoans. The myxospores morphology, histopathology and ssrDNA sequences supported a diagnosis of T. pyriformis from tench and T. cf. fuhrmanni from common nase.

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Two Thelohanellus spp. were redescribed from cyprinid fishes.

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Thelohanellus pyriformis was recorded and described from the type host tench (Tinca tinca).

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Thelohanellus cf. fuhrmanni was found in an atypical host, common nase (Chondrostoma nasus).

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The morphology of both Thelohanellus species was supported by histology and ssrDNA sequence data.

Two new species of Myxobolus Bütschli, 1882 (Cnidaria: Bivalvulida: Myxobolidae) infecting the gill of the black redhorse, Moxostoma duquesnei (Lesueur) (Cypriniformes: Catostomidae) in the Little Tennessee River Basin, North Carolina

Two new species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) are described from the gill of the black redhorse (Moxostoma duquesnei [Leueur][Cypriniformes: Catostomidae]) from the Little Tennessee River Basin, North Carolina, United States. Myxobolus branchiofilum n. sp. infects lumen of the lamellar arterioles and Myxobolus branchiopecten n. sp. infects the bone and cartilage at the tip of the gill rakers. They differ from all congeners by a combination of myxospore dimensions and the presence or absence of an iodinophilic vacuole in the sporoplasm, mucous envelope, intercapsular process, and sutural markings. A phylogenetic analysis of the small subunit ribosomal DNA recovered M. branchiopectin sister to Myxobolus sp. (AF378343) in a clade composed of 6 species of Myxobolus, which infect predominately cypriniform intermediate hosts. Myxobolus branchiofilum was recovered sister to Myxobolus ictiobus Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise & Pote, 2016 in a clade composed of 8 species of Myxobolus, which predominately infect catostomid intermediate hosts. Histological sections of infected gill revealed intra-lamellar plasmodia of M. branchiofilum in the lumen of the lamellar arterioles and foci of M. branchiopecten developing in the bone and cartilage of the gill raker tip. These are the first myxozoans reported from the black redhorse. Given that these two new species are morphologically congeneric but recovered in distantly related clades, we discuss the persistent issue of myxobolid genera paraphyly/polyphyly.

A NEW SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE BLUE SUCKER, CYCLEPTUS ELONGATUS (LESUEUR) (CYPRINIFORMES: CATOSTOMIDAE: CYCLEPTINAE), FROM ARKANSAS

During 9-10 February 2018 and 21-22 February 2020, 7 adult Blue Suckers, Cycleptus elongatus, were collected by hoop nets from the Red River, Little River County (n = 3), and the Black River, Lawrence County (n = 4), Arkansas, and their gills, gallbladders, fins, integument, other major organs, and musculature were examined for myxozoans. All 7 (100%) were infected with an unknown species of gill-infecting Myxobolus sp. Twenty formalin-fixed plasmodia (cysts) of Myxobolus cloutmani n. sp. were elliptoidal, 407 μm long × 270 μm wide. Formalin-fixed myxospores were orbicular to broadly elliptoidal, 8.7 μm long × 7.8 μm wide. Two polar capsules were pyriform and subequal in size, extending over halfway in the myxospore. The larger polar capsule was 5.5 μm long × 3.1 μm wide, while the shorter was 5.1 × 2.9 μm. A coiled polar filament possessed 5 or 6 coils. The myxospore was 3.7 μm thick in sutural view, with a distinct sutural ridge. Qualitative and quantitative morphological data were from formalin-fixed as well as ethanol-preserved spores, while molecular data consisted of a 2,010 base pair sequence of the partial 18S ribosomal RNA gene and a 2,502 base pair sequence of the partial 28S ribosomal RNA gene. Phylogenetic analysis grouped M. cloutmani n. sp. with the other catostomid-infecting myxobolids. This is the first myxozoan reported from C. elongatus.

Sphaerospora festivus n. sp., a parasite of the flag cichlid, Mesonauta festivus (Teleostei: Cichlidae) from eastern Amazon, Brazil

The present study describes a new species of the genus Sphaerospora found in the urinary bladder of the flag cichlid, Mesonauta festivus collected in Corre Água district of the municipality of Macapá, Amapá State (Brazil). The study includes morphological and phylogenetic analyses of the new parasite, to determine the relationship of the new species with related myxosporean species. The new species has polysporous plasmodia, which vary in size and shape. The mature myxospores are subspherical shape in valvar view. In the sutural view, the myxospores are 5.3±0.2 (5.2-5.6) μm in length and 7.0±0.7 (6.3-7.7) μm in width, with two piriform polar capsules equal size, 2.5±0.2 (2.3-2.8) μm in length and 1.8±0.2 (1.6-2.0) μm in width. The phylogenetic analyses of a partial sequence of the 18S rRNA gene confirmed the status of the new species and determined the relationship of the new species and related myxosporean species.The sum of the evidence indicates that, Sphaerospora festivus n. sp. belongs to the family Sphaerosporidae, and is the first record of the genus Sphaerospora from Brazil.

Description of Myxidium pseudocuneiforme n. sp. (Myxosporea: Myxidiidae) from Cyprinus carpio in China, with the Resolution on a Taxonomic Dilemma of Myxidium cuneiforme

Investigations on myxozoan parasites of fish from Chongqing in China, revealed two Myxidium cuneiforme-like myxosporeans infecting the gallbladder of Cyprinus carpio carpio and Carassius auratus. We researched their myxospore morphology, and analyzed their genetic similarity and phylogenic relationships to other myxozoans based on small subunit ribosomal DNA (18S rDNA) sequences. Although both parasites recovered were morphologically similar, the myxosporean isolated from C. auratus was consistent in morphology to Myxidium cuneiforme, which was described from this host species. The parasite isolated from C. c. carpio had overlapping myxospore dimensions to M. cuneiforme, but on average, the polar capsules were not as long. More importantly, this parasite was genetically distinct from M. cuneiforme with 96.3% and 96.5% similarity in two sequences of 18S rDNA, and we propose the name Myxidium pseudocuneiforme n. sp. for this myxozoan from common carp. Its mature myxospores are ellipsoidal and asymmetric with pointed ends in valvular view, arc-shaped or fusiform in sutural view. The pyriform polar capsules are equal in size, and polar filament with 5-6 coils. This study highlights that molecular characteristics and host specificity are indispensable for myxozoan species identification when presented with the taxonomic dilemma of whether we are observing one species that exhibits slight morphological differences or multiple, but similar, species in different hosts.

A new species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) infecting stratum spongiosum of the imperiled sicklefin redhorse, Moxostoma sp. (Cypriniformes: Catostomidae) from the Little Tennessee River, North Carolina, USA

The sicklefin redhorse, Moxostoma sp. (Cypriniformes: Catostomidae), is an innominate imperiled catostomid endemic to the Hiwassee and Little Tennessee river basins, which has been restricted to a few tributaries of these systems by impoundments. During collections to propagate sicklefin redhorse for reintroduction, a myxozoan, described herein, was observed infecting sicklefin redhorse in the Little Tennessee River Basin, North Carolina. Myxobolus naylori Ksepka et Bullard sp. n. infects the stratum spongiosum covering the scales of sicklefin redhorse. Myxospores of the new species differ from all congeners by the combination of having a mucous envelope, intercapsular process, and sutural markings as well as lacking an iodinophilic vacuole in the sporoplasm. A phylogenetic analysis of the 18S rDNA gene recovered the new species in a polytomy with Myxobolus marumotoi Li et Sato, 2014 and a clade comprised of species of Myxobolus Bütschli, 1882; Thelohanellus Kudo, 1933, and Dicauda Hoffman et Walker, 1973. Histological sections of infected sicklefin redhorse skin revealed myxospores within a plasmodium in the stratum spongiosum dorsal to scales, encapsulated in collagen fibres, and associated with focal erosion of scales directly beneath the plasmodium; in some instances, the scale was perforated by the plasmodium. The specificity of the new species to sicklefin redhorse may make it a useful biological tag to differentiate sicklefin redhorse from morphologically similar species. The new species is the first parasite reported from sicklefin redhorse, a species of concern to the United States Fish and Wildlife Service. No species of Myxobolus has been reported from species of Moxostoma in the Southeast United States. As it was observed that Myxobolus minutus Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise et Pote, 2016 is a primary junior homonym of Myxobolus minutus Nemeczek, 1911, we propose the replacement name Myxobolus diminutus (Rosser, Griffin, Quiniou, Alberson, Woodyard, Mischker, Greenway, Wise et Pote, 2016).

A New Species of ThelohanellusKudo, 1933 (Myxozoa: Bivalvulida) Infecting Skeletal Muscle of Blacktail Shiner, Cyprinella venusta Girard, 1856 (Cypriniformes: Cyprinidae) in the Chattahoochee River Basin, Georgia

Thelohanellus magnacysta n. sp. (Bivalvulida: Myxobolidae) infects the skeletal muscle of blacktail shiner, Cyprinella venusta Girard, 1856 (Cypriniformes: Cyprinidae) in Bull Creek, Chattahoochee River Basin, eastern Georgia. Although numerous members of ThelohanellusKudo, 1933 have overlapping myxospore dimensions with the new species, it differs from all nominal congeners by polar filament coil number and polar capsule width as well as by lacking a mucous envelope, iodinophilic vacuole, and sutural markings. With the use of novel primers for Myxozoa, a phylogenetic analysis of the small subunit ribosomal DNA (SSU rDNA) suggests that the new species shares a recent common ancestor with a clade of cyprinid-infecting species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) and Thelohanellus. Consistent with other published research concerning the systematics of Thelohanellus, this result suggested that Thelohanellus and Myxobolus are polyphyletic and need revision. Histological sections of infected blacktail shiners confirmed that myxospores were only found within a plasmodium and only infected skeletal muscle and that plasmodia were encapsulated by a granuloma comprising varying degrees of acute granulomatous inflammation. The new species is the fourth of Thelohanellus reported from North America and the first reported from Cyprinella, as well as the first myxozoan described from the blacktail shiner.