Small intestinal flukes of the genus Metagonimus (Digenea: Heterophyidae) in Europe and the Middle East: A review of parasites with zoonotic potential.

The heterophyid trematode Metagonimus romanicus (Ciurea, 1915) (Digenea) is redescribed on the basis of type material from domestic dogs (Canis familiaris) in Romania, vouchers from experimentally infected cats (Felis catus) and adults recovered from golden hamsters (Mesocricetus auratus) infected with metacercariae from scales of chub (Squalius cephalus) and common nase (Chondrostoma nasus) (Cypriniformes: Leuciscidae) in Hungary. This trematode, endemic to Europe and neighbouring regions (northwestern Türkiye), was previously misidentified as M. yokogawai (Katsurada, 1912), a zoonotic parasite of humans in East Asia. However, the two species differ considerably both genetically and morphologically, e.g., in the position of the ventral sucker, the presence of the prepharynx, the anterior extent of the vitelline follicles and the posterior extent of the uterus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), described from domestic cats and dogs in Israel, is a valid species distributed in the Middle East and Transcaucasia, which is also confirmed by molecular data. It differs from all Metagonimus species, including M. romanicus, in having symmetrical testes instead of the oblique testes of the other congeners. The zoonotic significance of M. romanicus and M. ciureanus is unclear, but appears to be low in Europe, mainly because raw or undercooked, whole fish with scales are generally not consumed. Accidental infection of fishermen by metacercariae in the scales when cleaning fish is more likely, but has never been reported. Remains of cyprinoids with scales infected with metacercariae of Metagonimus spp. can be an important natural source of infection for dogs, cats, and other carnivores, which can serve as a reservoir for these parasites.

Title: Petits trématodes intestinaux du genre Metagonimus (Digenea : Heterophyidae) en Europe et au Moyen-Orient : revue de parasites à potentiel zoonotique. Abstract: Le trématode Heterophyidae Metagonimus romanicus (Ciurea, 1915) (Digenea) est redécrit sur la base de matériel type provenant de chiens domestiques (Canis familiaris) en Roumanie, de vouchers issus de chats (Felis catus) infectés expérimentalement et d'adultes collectés chez des hamsters dorés (Mesocricetus auratus) infectés par des métacercaires provenant d'écailles de chevesne commun (Squalius cephalus) et de nase commun (Chondrostoma nasus) (Cypriniformes : Leuciscidae) de Hongrie. Ce trématode, endémique d'Europe et des régions voisines (nord-ouest de la Turquie), avait été précédemment identifié à tort comme étant M. yokogawai (Katsurada, 1912), un parasite zoonotique des humains en Asie de l'Est. Cependant, les deux espèces diffèrent considérablement sur le plan génétique et morphologique, par exemple par la position de la ventouse ventrale, la présence du prépharynx, l'étendue antérieure des follicules vitellins et l'étendue postérieure de l'utérus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), décrite chez des chats et des chiens domestiques en Israël, est une espèce valide répartie au Moyen-Orient et en Transcaucasie, ce qui est également confirmé par des données moléculaires. Cette espèce diffère de toutes les espèces de Metagonimus, y compris M. romanicus, par ses testicules symétriques au lieu des testicules obliques des autres congénères. L'importance zoonotique de M. romanicus et M. ciureanus n'est pas claire, mais semble faible en Europe, principalement parce que les poissons n'y sont généralement pas consommés crus ou insuffisamment cuits et entiers avec les écailles. L'infection accidentelle des pêcheurs par des métacercaires présents dans les écailles lors du nettoyage du poisson est plus probable mais n'a jamais été signalée. Les restes de poissons cyprinoïdes avec les écailles, infectés par des métacercaires de Metagonimus spp. peuvent être une source naturelle importante d'infection pour les chiens, les chats et autres carnivores, qui peuvent servir de réservoir à ces parasites.

Morphological and molecular characterisation of two closely related species: Myxobolus tihanyensis n. sp. and Myxobolus sandrae Reuss, 1906.

Based on spore morphology and small subunit ribosomal DNA sequences, we describe a new Myxobolus species, Myxobolus tihanyensis n. sp., parasitizing the European perch (Perca fluviatilis) from Lake Balaton in Hungary. The brownish plasmodia were found in various locations of the body, mainly in the muscle adjacent with fins and vertebrae. The spores were ovoid, and measured 9.84 ± 0.38 µm in length, 7.69 ± 0.23 µm in width, and 5.35 ± 0.21 µm in thickness, with 8-10 sutural (edge) markings. The polar capsules were mostly equal in size, with 4.91 ± 0.39 µm in length and 2.27 ± 0.24 µm in width. The polar tubule length is 38.15 µm ± 2.70, and coiled 6-7 times. In particular, these morphological data overlap with those of Myxobolus sandrae Reuss1906 infecting the European perch (Perca fluviatilis), the pikeperch (Sander lucioperca), and the Volga pikeperch (Sander volgensis) according to previous descriptions and the taxonomic data here described. However, the phylogenetic analyses separate the two species as sister clades with 16.8% genetic distance. This study has demonstrated that the two species of Myxobolus exhibit phenotypic similarity while displaying significant genetic divergence. Therefore, the importance of including molecular data in the taxonomic description of myxozoans is emphasized.

The first detection of Myxobolus lentisuturalis Dyková, Fiala et Nie, 2002, a highly pathogenic muscle-infecting parasite of gibel carp (Carassius auratus gibelio Berg, 1932) in Hungary.

Myxobolus lentisuturalis is a myxosporean parasite infecting the musculature both of goldfish (Carassius auratus auratus) and gibel carp (Carassius auratus gibelio). The species was originally described in China from gibel carp that is a common fish for sport fishing in Hungary meanwhile is one of the most popular farmed fish in China due to its high demand. Eighteen gibel carp with distortions were collected from a barrage pond in southern Hungary. All fish had large humps in the dorsolateral region due to infection of the muscle between the head and the dorsal fin. The swollen degenerated tissue was filled with myxozoan spores, which were collected for morphological and molecular studies. By size and morphology, the spores were consistent with morphological description of M. lentisuturalis. Histopathological examination showed that the formation of plasmodia containing myxospores leads to severe destruction of muscle tissue. The 18S ribosomal DNA and 28S ribosomal DNA data of the samples presented matched with previous sequences of M. lentisuturalis in GenBank. Phylogenetic analyses confirmed that our sequences belong to a monophyletic group with them supported by a high bootstrap. This study highlights the occurrence of a highly pathogenic myxozoan, M. lentisuturalis in Hungary as a new geographical location.

Molecular evidence of the absence of Metagonimus yokogawai (Katsurada, 1912) in Europe: report of Metagonimus sp. in cyprinoid fish from the River Danube in Hungary.

Trematodes of the genus Metagonimus Katsurada, 1912 (Digenea: Heterophyidae) are zoonotic parasites that cause infections in humans, with most cases reported in Southeast Asia. Larvae from the second intermediate host, called metacercariae, of one of human-infecting species, M. yokogawai (Katsurada, 1912), have been reported from cyprinoid fish in Europe. In the present study, we provided DNA-based evidence that metacercariae of Metagonimus, which are commonly found in the scales of various cyprinoids in Central Europe (Danube River in Hungary) do not belong to M. yokogawai. Sequence analysis of the ITS region, 28S rDNA, and cox1 genes showed that this species is clearly distinct from all Asian species, including M. yokogawai, which probably does not occur in Europe. Metacercariae from cyprinoids might belong to Metagonimus romanicus (Ciurea, 1915), an insufficiently known species described from Romania.

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.

Threat of cercarial dermatitis in Hungary: A first report of Trichobilharzia franki from the mallard (Anas platyrhynchos) and European ear snail (Radix auricularia) using molecular methods.

Cercarial dermatitis in humans is a re-emerging zoonotic disease caused by infectious larvae of avian blood flukes within the Schistosomatidae family. Upon water contact, these avian schistosome larvae directly penetrate human skin and cause irritation. Between September 2018 and September 2020, carcasses of 94 mallards (Anas platyrhynchos), two green-winged teals (Anas crecca) along with one ferruginous duck (Aythya nyroca) were examined. Birds were collected within 12 regions of Hungary, representative of 9 different counties. Inspecting both morphological characters and molecular data, the cytochrome oxidase subunit I (COI) and large subunit ribosomal DNA (LSU rDNA) sequences, Bilharziella polonica and Dendritobilharzia pulverulenta were each identified. Most importantly, Trichobilharzia franki was found for the first time in Hungary and in 5 dispersed counties in conjunction with of 3 counties where other avian schistosomes were found. Of note, these avian blood flukes were predominately encountered in wild mallards (∼50%) and not in birds reared for hunting (∼1%). In total, 245 European ear snails (Radix auricularia), a known intermediate host of Trichobilharzia spp., were collected from an urban pond in Eger, Hungary. Five snails (∼2%) consistently shed numerous furcocercariae of T. franki that were confirmed by molecular methods. Our findings help to pinpoint a contemporary life cycle of this avian schistosome within an urban environment, a location regularly visited by various wild waterfowl and the possible species of avian schistosomes responsible for cercarial dermatitis in Hungary. Taken as a whole, we demonstrate the actual and potential risk zone for cercarial dermatitis, particularly with reference to R. auricularia distributions, within Hungary and across Central Europe.

Extreme pathological symptom generated by Dermocystidium koi infection of common carp (Cyprinus carpio L.) in Hungary.

Dermocystidiosis in common carp (Cyprinus carpio L.) as a skin infection in the form of small, pea-sized bulging nodules is well-known in Hungary. Its occurrence is sporadic, and the pathogenic effect is generally moderate. Nonetheless, here we report an unusual case of the infection when a mass of dermocystid spore-filled hyphae-like cysts formed a large tumour-like nodule under the skin intruding deeply in the red muscle on one side occipital region of the fish body. Histological sections showed that the tumour-like nodule was composed of two layers, a pale peripheral part with a high mass of cysts surrounded by some cell debris of muscle cells and a dark central part with a less dense meshwork of tubular cysts which were embedded in the partially damaged red muscle tissue. No infection was found in the white muscle. Sequences of 18S rDNA of spores from the tumour-like nodule showed a complete identity to sequences from typical bulging nodules in skin. They were also highly similar to the sequences of D. anguillae clones (99.5%-99.4%), to some samples of D. salmonis (99.7% and 99.4%), and to the Dermocystidium sp. CM-2002 (99.4%) from European perch.

The occurrence of known Myxobolus and Thelohanellus species (Myxozoa, Myxosporea) from Indian major carps with the description of Myxobolus bandyopadhyayi n. sp. in West Bengal.

Myxosporean infection of Indian major carps (rohu, Labeo rohita; catla, Gibelion catla; mrigal, Cirrhinus mrigala) was examined from two fish farms and two fish markets in West Bengal, India. One Thelohanellus and four Myxobolus species were detected from the fins and scales of the investigated species. Comprehensive morphological and molecular biological studies revealed four already known species, Thelohanellus caudatus from the fins of rohu, Myxobolus dermiscalis from the scales of rohu, Myxobolus chakravartyi from the fins of catla, and Myxobolus rewensis from the fins of mrigal. This study complemented the species description of M. chakravartyi and M. rewensis with the missing molecular data. Moreover, based on morphometrics and ssrDNA sequence data, a new species was documented from the scales of rohu, and named Myxobolus bandyopadhyayi n. sp.

New data on Thelohanellus nikolskii Achmerov, 1955 (Myxosporea, Myxobolidae) a parasite of the common carp (Cyprinus carpio, L.): The actinospore stage, intrapiscine tissue preference and molecular sequence.

Thelohanellus nikolskii, Achmerov, 1955 is a well-known myxozoan parasite of the common carp (Cyprinus carpio L.). Infection regularly manifests in numerous macroscopic cysts on the fins of two to three month-old pond-cultured carp fingerlings in July and August. However, a Thelohanellus infection is also common on the scales of two to three year-old common carp in ponds and natural waters in May and June. Based on myxospore morphology and tissue specificity, infection at both sites seems to be caused by the same species, namely T. nikolskii. This presumption was tested with molecular biological methods: SSU rDNA sequences of myxospores from fins of fingerlings and scales of older common carp were analysed and compared with each other and with related species available in GenBank. Sequence data revealed that the spores from the fins and scales represent the same species, T. nikolskii. Our study revealed a dichotomy in both infection site and time in T. nikolskii-infections: the fins of young carp are infected in Summer and Autumn, whereas the scales of older carp are infected in Spring. Myxosporean development of the species is well studied, little is known, however about the actinosporean stage of T. nikolskii. A previous experimental study suggests that aurantiactinomyxon actinospores of this species develop in Tubifex tubifex, Müller, 1774. The description included spore morphology but no genetic sequence data (Székely et al., 1998). We examined >9000 oligochaetes from Lake Balaton and Kis-Balaton Water Reservoire searching for the intraoligochaete developmental stage of myxozoans. Five oligochaete species were examined, Isochaetides michaelseni Lastochin, 1936, Branchiura sowerbyi Beddard, 1892, Nais sp., Müller, 1774, Dero sp. Müller, 1774 and Aelosoma sp. Ehrenberg, 1828. Morphometrics and SSU rDNA sequences were obtained for the released actinospores. Among them, from a single Nais sp., the sequence of an aurantiactinomyxon isolate corresponded to the myxospore sequences of T. nikolskii.

Mycoplasma infections in freshwater carnivorous fishes in Hungary.

The abundance of mycoplasma-like microorganisms seems to be common in the intestinal tract of fish, but their occurrence in other organs can be considered pathological. Isolation of piscine mycoplasmas is essential to prove their virulence. In this study, a total of 100 specimens of nine freshwater fish species collected from natural waters and fish farms were analysed for the prevalence of mycoplasmas in different extraintestinal organs. Our results demonstrate that mycoplasmas are present in carnivorous fish (pike, wels catfish, black bullhead and pike perch) than in cyprinids more frequently. Among the surveyed organs, they colonize mainly the gills, the kidney and the livers. Although mycoplasmas could be detected in one-fifth of samples by molecular assays, the isolation of mycoplasmas belonged to the M. sualvi cluster within the hominis group of Mycoplasmataceae, but was separate from M. mobile, has been successful only from some specimens originated from wels catfish that was feasible only by special preparation steps (prefreezing, filter sterilization and incubation conditions (long culturing period, etc.). The low-efficiency of isolation trials indicates an extensive gap in our knowledge about piscine mycoplasmas, especially in the field of their nutritional requirements.

Digenean trematodes in Hungarian freshwater aquacultures.

Occurrence of metacercariae of potentially zoonotic trematodes (Platyhelminthes: Digenea) in the musculature of common carp (Cyprinus carpio L. 1758) was monitored in four Hungarian aquacultures. Four geographically distinct fish farms (located in the Northwestern, Southwestern, Northeastern and Southeastern parts of Hungary) were selected for the investigation. From each farm, a total of 258 one-summer-old fingerlings were sampled and examined in the years 2016 and 2017. In addition, in 2017, we examined 60 market size specimens (30 two-summers and 30 three-summers) sampled from the most infected aquaculture in the Northeastern part of Hungary. The fish were euthanized and decapitated whereafter their musculature (fillets) was digested in a pepsin solution to isolate metacercariae from the tissue whereafter morphological and molecular analyses (PCR and sequencing of ITS region) were performed. Opisthorchiid metacercariae were not recovered but in one of the farms numerous metacercariae were detected in the musculature of carp. They were identified as cyathocotylid trematodes based on their morphological characteristics and by sequencing the ITS region. The infection levels proved to be remarkably different among the four fish farms. Carps from the Northeastern farm were infected by large numbers of cyathocotylid metacercariae, while 8 Posthodiplostomum cuticola metacercariae were detected in the Northwestern aquaculture. In the other two farms (Southwestern and Southeastern) no infection was recorded. The infected farm is located close to a protected natural wetland habitat populated by a rich fauna of aquatic birds (potential final hosts) and snails (first intermediate host) which may create a higher risk of infection in the neighbouring fish farms.

Description of myxosporeans (Cnidaria: Myxozoa) infecting the popular food fish Notopterus notopterus (Pisces: Notopteridae) in Malaysia and India.

This study was a co-operative investigation of myxosporean infections of Notopterus notopterus, the bronze featherback, which is a popular food fish in the South Asian region. We examined fish from Lake Kenyir, Malaysia and the River Ganga, Hastinapur, Uttar Pradesh, India, and observed infections with two myxosporeans: Myxidium cf. notopterum (Myxidiidae) and Henneguya ganapatiae (Myxobolidae), respectively. These species were identified by myxospore morphology, morphometry and host tissue affinity, and the original descriptions supplemented with small-subunit ribosomal DNA sequences and phylogenetic analysis. Free myxospores of M. cf. notopterum were found in the gallbladder, and measured 14.7 ±â€¯0.6 µm long and 6.3 ±â€¯0.6 µm wide; host, tissue and myxospore dimensions overlapped with the type, but differed in morphological details (spore shape, valve cell ridges) and locality (Malaysia versus India). Plasmodia and spores of H. ganapatiae were observed in gills, and myxospores had a spore body 9.7 ±â€¯0.4 µm long, 4.5 ±â€¯0.5 µm wide; sample locality, host, tissue, spore morphology and morphometry matched the original description. Small-subunit ribosomal DNA sequences were deposited in GenBank (M. cf. notopterum MT365527, H. ganapatiae MT365528) and both differed by >7% from congeneric species. Although the pathogenicity and clinical manifestation of myxozoan in humans are poorly understood, consumption of raw fish meat with myxozoan infection was reported to be associated with diarrhea. Identification of current parasite fauna from N. notopterus is an essential first step in assessing pathogen risks to stocks of this important food fish.

Infection of the Carpathian brook lamprey (Eudontomyzon danfordi Regan, 1911) with a dermocystid parasite in the Tisza River Basin, Hungary.

The Carpathian brook lamprey (Eudontomyzon danfordi Regan, 1911) is an endemic protected species of Cephalaspidomorphi in the Carpathian Basin. No parasites have become known from these jawless vertebrates to date. Here, the authors describe an infection from a single specimen manifesting in protuberant skin cysts 7-10 mm in diameter, scattered on the body surface. Similar dermal infection was observed in 25 of the 274 lampreys recorded in the population survey. Skin cysts filled with round spore-like structures of a dermocystid parasite were found. These particles measured 8-14 µm in diameter and had an about 0.5 µm thick wall, and containing mainly a granular mass and a relatively scarce plasma. No hyphae were recorded. Despite conspicuous morphological changes in the skin, no inflammatory reactions were found. The molecular analysis of 18S rDNA showed similarity to dermocystid species of several fish species but differed from them approximately by 2%. This is the first record of a dermocystid parasite infecting a jawless vertebrate.

New record of metacercariae of the North American Posthodiplostomum centrarchi (Digenea, Diplostomidae) in pumpkinseed (Lepomis gibbosus) in Hungary.

Two species of the genus Posthodiplostomum (Digenea: Diplostomatidae) (Posthodiplostomum brevicaudatum Nordmann, 1832 and Posthodiplostomum cuticola Nordmann, 1832) are known as parasites of Hungarian native fishes. Metacercariae of P. cuticola are widespread in Europe and cause black spot disease. Several species of Posthodiplostomum were described also from North America but none of them has been isolated in Hungary up to now. Posthodiplostomum centrarchi Hoffman, 1958 has been detected recently in pumpkinseeds (Lepomis gibbosus L., 1758) in several European countries. Posthodiplostomum centrarchi was isolated for the first time in Hungary from pumpkinseeds caught in the Maconka water reservoir in 2015. Thereafter, several natural waters (e.g. the River Danube, Lake Balaton and the Sió channel) were sampled in order to determine its presence and distribution. Only the native species P. cuticola was detected in Lake Balaton on cyprinids but a relatively high infection rate of P. centrarchi was observed in the Sió channel close to the lake. Pathological changes were absent, and metacercariae were mostly attached to the surface of the liver, kidney and heart. The phylogenetic analysis of the ITS and COI sequences of P. centrarchi and P. cuticola clustered into two distinct branches, which was in agreement with the morphological results.

Henneguya (Cnidaria: Myxosporea: Myxobolidae) infections of cultured barramundi, Lates calcarifer (Perciformes: Latidae) in an estuarine wetlands system of Malaysia: description of Henneguya setiuensis n. sp., Henneguya voronini n. sp. and Henneguya calcarifer n. sp.

Examination of 35 barramundi (Lates calcarifer) from aquaculture cages in Setiu Wetland, Malaysia, revealed a single fish infected with three Henneguya spp. (Cnidaria: Myxosporea). Characterization of the infections using tissue tropism, myxospore morphology and morphometry and 18S rDNA sequencing supported description of three new species: Henneguya setiuensis n. sp., Henneguya voronini n. sp. and H. calcarifer n. sp. Myxospores of all three species had typical Henneguya morphology, with two polar capsules in the plane of the suture, an oval spore body, smooth valve cell surfaces, and two caudal appendages. Spores were morphometrically similar, and many dimensions overlapped, but H. voronini n. sp. had shorter caudal appendages compared with H. calcarifer n. sp. and H. setiuensis n. sp. Gross tissue tropism distinguished the muscle parasite H. calcarifer n. sp. from gill parasites H. setiuensis n. sp. and H. voronini n. sp.; and these latter two species were further separable by fine-scale location of developing plasmodia, which were intra-lamellar for H. setiuensis n. sp. and basal to the filaments for H. voronini n. sp. small subunit ribosomal DNA sequences distinguished all three species: the two gill species H. setiuensis n. sp. and H voronini n. sp. were only 88% similar (over 1708 bp), whereas the muscle species H. calcarifer n. sp. was most similar to H. voronini n. sp. (98% over 1696 bp). None of the three novel species was more than 90% similar to any known myxosporean sequence in GenBank. Low infection prevalence of these myxosporeans and lack of obvious tissue pathology from developing plasmodia suggested none of these parasites are currently a problem for barramundi culture in Setiu Wetland; however additional surveys of fish, particularly at different times of the year, would be informative for better risk assessment.

Myxobolus infection in the cornea of the roach (Rutilus rutilus) in Lake Balaton.

Infection of the cornea in fishes by Myxobolus plasmodia is a common but still little known site preference of myxosporeans. A sporadic but striking infection in the cornea of the roach (Rutilus rutilus) was observed in Lake Balaton, Hungary. Relatively small, round plasmodia 250 to 500 µm in diameter developed in the dense connective tissue of the cornea. Morphological and molecular biological examination of spores collected from cysts in the cornea demonstrated that this infection is caused by Myxobolus fundamentalis, a species hitherto reported only from the cartilaginous gill arch of the roach. The 18S rDNA sequences of spores from the cornea showed 99.9% identity to the sequences of spores from the gill arch, and they also shared 99.9% identity with the sequences of triactinomyxon actinospores obtained from the oligochaete Isochaetides michaelseni.

Morphological, histological, and molecular description of Myxobolus ompok n. sp. (Myxosporea: Myxobolidae), a kidney myxozoan from Pabdah catfish Ompok pabda (Hamilton, 1822) (Siluriformes: Siluridae) in India.

In a parasitological survey of freshwater fishes near Meerut, Uttar Pradesh, India, myxozoan infections in Pabdah catfish Ompok pabda Ham. (Siluriformes: Siluridae) were found. Round plasmodia and scattered spores of Myxobolus ompok n. sp. were found in the kidney of the host. Plasmodia measuring 150-200 µm were located in the renal interstitium. Spores of Myxobolus ompok n. sp. were elongated pyriform, 13.6-14.4 (14.8 ± 0.42) µm long, 5.6-6.4 (6.5 ± 0.33) µm wide, and 5.2-6.4 (5.9 ± 0.43) µm thick with two equal polar capsules measuring 8.0-8.5 (8.2 ± 0.2) µm in length and 1.5-2.4 (1.8 ± 0.33) in width having six filamental turns. Both the morphology and DNA analysis of the 18S rRNA gene revealed that Myxobolus ompok n. sp. is distinct from previously described species of Myxobolus and shares no significant similarity with any other Myxobolus deposited in the GenBank database. Phylogenetic analysis inferred that this species showed the closest similarity to Myxobolus miyarii (KT001495). This is the first record of any Myxobolus sp. from O. pabda in India.

An investigation of the host-specificity of metacercariae of species of Apophallus (Digenea: Heterophyidae) in freshwater fishes using morphological, experimental and molecular methods.

Metacercariae of species of the genus Apophallus Lühe, 1909, infecting the fins and skin of freshwater fishes, frequently cause black spot disease. Two species, Apophallus muehlingi (Jägerskiöld, 1899) and A. donicus (Skrjabin & Lindtrop, 1919), are known to occur in Hungarian fishes. It has generally been thought that metacercariae of A. muehlingi infect cyprinid fishes, whereas those of A. donicus develop in percids. As part of a morphological, experimental and molecular study, metacercariae were collected from 99 infected specimens of five cyprinid hosts (Abramis brama, Blicca bjoerkna, Chondrostoma nasus, Squalius cephalus, Scardinius erythrophthalmus) and 18 infected specimens of two percid hosts (Gymnocephalus cernua, Perca fluviatilis) in Hungarian natural waters (Lake Balaton, River Danube). Moreover, 1024 common carp (Cyprinus carpio) specimens collected from Hungarian fish ponds were investigated for Apophallus infection, but without positive results. For reliable species identification, experimental infections of chicks were carried in order to produce adult specimens from metacercariae collected from the fins and skin of the cyprinid and percid hosts. Within 8 days, adult specimens of both A. muehlingi and A. donicus developed in chicks infected with metacercariae from the cyprinid common bream (Abramis brama) and the white bream (Blicca bjoerkna) and the ruffe (Gymnocephalus cernua), a percid, respectively. The morphology of the collected metacercariae and adult individuals developed in the feeding experiments was characterised. A molecular analysis was extended to cercarial samples from the snail Lithoglyphus naticoides and to a single adult specimen of Apophallus from a fox. Sequences of 28 specimens were analysed using molecular methods (sequencing the internal transcribed spacer region and the cytochrome oxidase I subunit). Phylogenetic analysis was executed, and the Apophallus samples clustered into three distinct branches using both genes, A. muehlingi from cyprinids, A. donicus from percids and, a third, previously unknown, Apophallus clade, also from cyprinids.

Molecular biological studies of adult and metacercarial stages of Petasiger exaeretus Dietz, 1909 (Digenea: Echinostomatidae).

Molnár et al. (2015) reported two types of echinostomatid metacercariae in the lateral line organ of Hungarian fish species. Type 1 metacercariae possessed 27 collar spines and 16 uniform and three larger dorsal spines, whereas Type 2 metacercariae bore 27 collar spines and 19 equal-sized dorsal spines. In the recent work, molecular studies carried out on the ITS region and partial 28S rDNA sequences of two types of echinostomatid metacercariae and the sequences of adult stages of the species of Petasiger Dietz, 1909 collected from cormorants (Phalacrocorax carbo L.) showed that some of the Type 2 metacercariae corresponded to Petasiger exaeretus Dietz, 1909, whereas other morphologically similar metacercariae were identified as Petasiger phalacrocoracis (Yamaguti, 1939). The sequences of the Type 1 metacercariae with three larger dorsal spines could not be identified with any of the known sequences from echinostomatid trematodes.

Redescription of Henneguya chaudhuryi (Bajpai & Haldar, 1982) (Myxosporea: Myxobolidae), infecting the gills of the freshwater fish Channa punctata (Bloch) (Perciformes: Channidae) in India.

During a survey of myxosporean parasites of freshwater fishes in Meerut, Uttar Pradesh (UP), India, spores of Henneguya chaudhuryi (Bajpai & Haldar, 1982) were found in the gill lamellae of the spotted snakehead fish Channa punctata (Bloch) (Perciformes: Channidae). This species was described lacking several characteristics in the original description, which makes challenging the accurate diagnosis. Here, we supplemented its description based on morphological, histological and molecular data. Plasmodia of H. chaudhuryi are oval, measuring 60-100 × 40-68 µm, located intralamellarly. Mature spores are elongate, measuring 10.5-13.2 × 3.6-4.2 µm, with two slightly unequal polar capsules with 6-7 filamental turns and two straight, equal caudal appendages, 10-17 µm long. Scanning electron microscopy revealed a flat surface. The 18S rDNA sequence for H. chaudhuryi did not show a close relationship with those of any other Henneguya spp., represented in the GenBank.