Myxosporean Species Research Articles

Myxobolus myleus n. sp. infecting the bile of the Amazonian freshwater fish Myleus rubripinnis (Teleostei: Serrasalmidae): morphology and pathology

Myxobolus myleus n. sp. is described from the gall-bladder of the freshwater fish Myleus rubripinnis collected near the city of Oriximiná in the Amazon System, Brazil. The spores obtained from the bile contained two equal symmetrical and smooth valves, each forming the spore wall. The spores were large, with a cone-like form, a semi spherical basal contour and measured (in μm) 19.3 ± 0.5 (n = 25) × 8.3 ± 0.5 (n = 25) × 4.0 ± 0.3 (n = 15). The apical end of the spores contained two elongate, equal and pointed conical polar capsules measuring 13.2 ± 0.4 μm (n = 25) in length and 3.0 ± 0.3 μm (n = 15) in width, each having a slightly tapering polar filament with 19 to 21 turns. The polar capsules were extended below at about 4/5 of the total length of the spores. The sporoplasm was binucleate and contained some sporoplasmosomes. All infected fish presented hypertrophy of the gall-bladder due to presence of the brownish parasite floating in the bile. In this paper we describe this new species of myxosporean based on light and ultrastructural observations, together with its associated pathology.

Identification of Kudoa septempunctata as the Causative Agent of Novel Food Poisoning Outbreaks in Japan by Consumption of Paralichthys olivaceus in Raw Fish

Outbreaks of an unidentified food-borne illness associated with the consumption of raw fish have increased in Japan since 2003. Those affected with this illness develop diarrhea and emesis within 2-20 hours after a meal including raw fish. No known causative agents such as bacteria, viruses, bacterial toxins, or toxic chemicals have been detected in the foods that were ingested. Fortunately, this illness is self-limiting with good prognosis in all cases. We conducted an epidemiological analysis of outbreaks that occurred during 2008 and 2010 and analysed a fish sample from one outbreak by metagenomic DNA sequencing, real-time polymerase chain reaction, and direct microscopic observations. The pathogenicity of a putative risk factor identified by these techniques was assessed using the suckling-mouse test and a house musk shrew emetic assay. The epidemiological analysis of outbreaks in 24 municipalities involving >1300 subjects implicated an olive flounder (Paralichthys olivaceus) as the causative food source. The presence of Kudoa septempunctata, a recently-described myxosporean species in P. olivaceus, was prevalent in the causative foods. K. septempunctata induced watery stools and an elevated fluid accumulation ratio in suckling mice, as well as vomiting in house musk shrews. These results identify K. septempunctata as the etiological agent of this novel food-borne illness outbreak associated with consumption of raw P. olivaceus. This is the first report, to our knowledge, demonstrating the human pathogenicity of Kudoa spores.

New species of Myxosporea from frogs and resurrection of the genus Cystodiscus Lutz, 1889 for species with myxospores in gallbladders of amphibians

Two new myxosporean species in the gallbladders of frogs have recently spread across eastern Australia and cause disease. Cystodiscus axonis sp. n. and Cystodiscus australis sp. n. are species of Myxosporea (Myxozoa) identified from a range of Australian frogs and tadpoles including the introduced Cane toad (Rhinella marina). The new species are defined by their distinct genetic lineage, myxospore morphology and ultrastructure of the pre-sporogonic development. Spores of both species are produced in the gallbladder. Spores of C. axonis sp. n. possess distinct filiform polar appendages (FPA). The pre-sporogonic development of C. axonis sp. n. is within myelinated axons in the central nervous system of hosts, as well as bile ducts of tadpoles. Pre-sporogonic and sporogonic development of C. australis sp. n. is confined to tadpole bile ducts and myxospores of C. australis sp. n. are devoid of FPA. The genus Cystodiscus Lutz, 1889 introduced for Cystodiscus immersus Lutz, 1889 is emended to accompany myxosporean parasites affecting amphibians previously classified in the genus Myxidium sensu lato. A synopsis of described species within Cystodiscus is provided.

One new Myxosporean species, Triangula cirrhini sp. nov., and one known species, T. ludhianae (syn. M. ludhianae Gupta and Khera, 1991) comb. n. (Myxozoa: Myxosporea), infecting Indian major carp in Harike wetland of Punjab

Myxozoans are important metazoan parasites infecting variety of fishes all over the world. During our study of myxosporean parasites of fishes of Harike wetland, India,Triangula cirrhinisp. nov. and one already known species,Triangula ludhianae(syn.M. ludhainaeGupta and Khera, 1991) were recorded from mucous membrane covering the epithelial lining of primary gill lamellae ofCirrhina reba(Ham.) (Cyprinidae: Cypriniformes). Spores of the first species,T. cirrhinisp. nov., measure 6.7 × 6.6 μm, triangular, bowl-shaped in valvular view having broad and flattened anterior end and narrow rounded posterior end. 4-5 prominent sutural edge markings (parietal folds) are present around the posterior margin of shell valves. In some spores, 7-8 sutural edge markings are also present all around the circumference. Polar capsules are two, equal measuring 3.3 × 3.1 μm, running parallel to each other, bottle-shaped with fine ducts opening divergently at the anterior corner of the spore. A very large intercapsular process is present. Spores of the second species,Triangula ludhianae(syn.M. ludhianaeGupta and Khera, 1991) measure 8.4 × 6.9 μm, conical in valvular view having broad and flattened anterior end and narrow blunt posterior end. Polar capsules are two, large, equal, measuring 3.3 × 3.0 μm and bottled-shaped with fine ducts opening wide apart at the anterior corners of the spore. An intercapsular process is absent but a crescent-shaped depression is present at the anterior end in the intercapsular space. In the present study,M. ludhianaeis transferred to the genusTriangulaon the basis of spore morphology.

Myxosporean hyperparasites of gill monogeneans are basal to the Multivalvulida

BackgroundMyxosporeans are known from aquatic annelids but parasitism of platyhelminths by myxosporeans has not been widely reported. Hyperparasitism of gill monogeneans by Myxidium giardi has been reported from the European eel and Myxidium-like hyperparasites have also been observed during studies of gill monogeneans from Malaysia and Japan.The present study aimed to collect new hyperparasite material from Malaysia for morphological and molecular descriptions. In addition, PCR screening of host fish was undertaken to determine whether they are also hosts for the myxosporean.ResultsHeavy myxosporean infections were observed in monogeneans from two out of 14 fish and were detected from a further five fish using specific PCRs and pooled monogenean DNA. Positive DNA isolates were sequenced and were from a single species of myxosporean. Myxospore morphology was consistent with Myxidium with histozoic development in the parenchymal tissues of the monogenean. Simultaneous infections in the fish could not be confirmed microscopically; however, identical myxosporean DNA could be amplified from kidney, spleen and intestinal tract tissues using the specific PCR. Small subunit (SSU) rDNA for the myxosporean was amplified and was found to be most similar (92%) to that of another hyperparasitic myxosporean from a gill monogenean from Japan and to numerous multivalvulidan myxosporeans from the genus Kudoa (89-91%). Phylogenetic analyses placed the hyperparasite sequence basally to clades containing Kudoa, Unicapsula and Sphaerospora.ConclusionsThe myxosporean infecting the gill monogenean, Diplectanocotyla gracilis, from the Indo-Pacific tarpon, Megalops cyprinoides, is described as a new species, Myxidium incomptavermi, based on a histozoic development in the monogenean host and its phylogenetic placement.We have demonstrated for the first time that a myxosporean hyperparasite of gill monogeneans is detectable in the fish host. However, myxospores could not be isolated from the fish and confirmation was by PCR alone. The relationship between the myxosporean infection in gill monogeneans and the presence of parasitic DNA in fish is not yet fully understood. Nonetheless, myxospores with a Myxidium-like morphology, two of which we have shown to be phylogenetically related, have now been reported to develop in three different gill monogeneans, indicating that myxosporeans are true parasites of monogeneans.

Supplementary studies on Henneguya doneci Schulman, 1962 (Myxozoa: Myxosporea) infecting the gill filaments of Carassius auratus gibelio (Bloch) in China: histologic, ultrastructural, and molecular data

Henneguya doneci Schulman, 1962 was collected from the gill filaments of Carassius auratus gibelio (Bloch) in Hubei Province, China. The plasmodia located on the surface of the gill arches deformed the neighboring gill filaments. The size of the plasmodia ranged from 0.6 to 4.5 mm in diameter in different months. The myxospores in the plasmodia measured 10.1 (9.2-11.5) μm long × 8.0 (7.5-8.5) μm wide × 7.5 (7-8) μm thick, with two equal capsules at 4.7 (4-5.5) μm long × 3.3 (2.5-4) μm wide, and two caudal processes 32.7 (24-38.5) μm long, respectively. Polar filaments were coiled 5-6 turns. Ultrastructural observation of the plasmodia showing the capsulogenesis of H. doneci is described briefly. The external tubule initially invaginated into the polar capsule. The rudimentary polar filaments were observed to undergo a series of considerable modification, finally developing into mature polar filaments. Molecular analysis demonstrated that although the myxosporean species were collected from different tissues of hosts in various geographic locations, they clustered with the Cyprinidae-infecting myxosporean species in the phylogenetic tree.

Henneguya cynoscioni sp. n. (Myxosporea: Bivalvulida), an agent of severe cardiac lesions in the spotted seatrout, Cynoscion nebulosus (Teleostei: Sciaenidae)

A new myxosporean species, Henneguya cynoscioni sp. n., is described from the spotted seatrout, Cynoscion nebulosus (Cuvier) (Sciaenidae) as a causative agent of cardiac henneguyosis. This new myxosporean species is characterized by the morphology of spores and the sequence of SSU rDNA. Examination of 227 spotted seatrout from four South Carolina estuaries in 2008-2010 revealed a 33.5% total prevalence of H. cynoscioni. Henneguya cynoscioni produces lesions in the bulbus arteriosus, its specific site of infection. The severity of lesions and their impact on the bulbus arteriosus is proportional to the number of plasmodial stages developing in this segment of the heart, being most pronounced in host reaction directed against spores liberated from plasmodia.

Two new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida) infecting an Indian major carp and a cat fish in wetlands of Punjab, India

A survey of parasites of freshwater fishes in Kanjali and Harike wetlands of Punjab (India) revealed the presence of two new myxosporean species belonging to the genus Myxobolus Bütschli (Winter (ed): Protozoa, 1882). Spores of the first species, M. saugati sp. nov. parasitizing scales of Labeo rohita (Cypriniformis: Cyprinidae) vern. rohu are characterized in having 'spores measuring 8.3×6.6μm in size, oval to spherical in valvular view having rounded anterior and posterior ends; polar capsules are two, equal, measuring 4.0×2.4μm, pyriform with distinct neck at the anterior end; an intercapsular process is absent'. Spores of the second species, Myxobolus szekeli sp. nov. parasitizing internal wall of stomach of Wallago attu (Cypriniformis: Siluridae) vern. mulle are '8.7×4.1μm in size, elongately ovoidal in valvular view having tapering, bluntly pointed anterior end and rounded posterior end; polar capsules are two, equal, measuring 4.4×1.5μm, tubular with blunt anterior and rounded posterior ends; polar capsules converge anteriorly but are placed at a distance posteriorly and occupies nearly half of the spore body cavity; an intercapsular process is absent'.

Sphaerospora elwhaiensis sp. n. (Myxosporea: Sphaerosporidae) from landlocked sockeye salmon Oncorhynchus nerka (Salmoniformes: Salmonidae) in Washington State, USA

A new species of sphaerosporid myxosporean, Sphaerospora elwhaiensis sp. n., is described from kidney of non-anadromous sockeye salmon (kokanee) Oncorhynchus nerka (Walbaum) from Lake Sutherland in the northern Olympic Peninsula, Washington, USA. Infection with the parasite was detected in 45% of 177 kokanee examined over 5 years. While conforming to the morphological criteria by which members of the genus are defined, the parasite is distinguished from congeners in salmonids of western North America by a unique combination of valvular sculpting of the myxospore, the relatively large size of the myxospore and monosporous development within the pseudoplasmodium. In addition, nucleotide sequences of the parasite's small and large subunit ribosomal RNA gene are unique. Phylogenetic analyses of these sequences suggested that the parasite is most closely related to freshwater Myxidium spp. and Zschokkella spp. The molecular data have provided further evidence for a polyphyletic association previously recognized among members of the genus and emphasize the need for a taxonomic revision of Sphaerospora Thélohan, 1892 and related genera.

Myxobolus harikensis sp. nov. (Myxozoa: Myxobolidae) infecting fins of Cirrhina mrigala (Ham.)—an Indian major carp in Harike Wetland, Punjab (India)

During a study of myxosporean parasites of freshwater fishes of Punjab Wetlands, India, one new myxosporean species, Myxobolus harikensis sp. nov. was recorded from the caudal fin of Cirrhina mrigala (Ham.) (Cypriniformes: Cyprinidae). Plasmodia are small, white, spherical-to-rounded and are present on the caudal fin (in between the fin rays) having two to five spores per plasmodium. Spores of M. harikensis measure 10.1 × 8.5 μm in size, pyriform in valvular view and lenticular in sutural view pointing in the direction to the plane of slightly bent sutural line. Shell valves are thick, smooth, asymmetric and flattened at the sutural plane. Parietal folds are absent. Polar capsules are two, prominently unequal, broadly pyriform-to-rounded in shape and lie at different levels in the spore body cavity. The larger polar capsule is 5.0 × 3.1 μm in size, placed anteriorly on the sutural plane and opening to the exterior anteriolaterally. The smaller polar capsule measures 1.7 × 1.4 μm in size, placed posteriorly, perpendicular to the sutural plane and opening to the exterior mediolaterally. Spores of M. harikensis closely resembles to that of Myxobolus africanus in having polar capsules placed at different levels in the spore body cavity, however, are unique in having unequal polar capsules both discharging laterally.

Two new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida) infecting an Indian major carp in Ropar and Kanjali wetlands (Punjab)

In India, more than 104 species of Myxobolus are recorded infecting freshwater and marine fishes. During our study on the myxozoan parasites of fishes of Punjab wetlands, India, two new myxosporean species, Myxobolus ropari sp. nov. and Myxobolus kanjali sp. nov. were recorded from mucous membrane around gill lamellae and scales of Cirrhina mrigala (Ham.), respectively. Spores of the first species, M. ropari sp. nov. measure 12.58×4.5μm in size, elongately pyriform, slender in shape with a pointed anterior end and a rounded posterior end. Polar capsules are two, equal, elongately pyriform, measuring 4.96×1.50μm in size, placed posteriorly from the tip of the spore running parallel to each other. Spores of the second species, M. kanjali sp. nov. measure 9.5×7.7μm in size, spherical in shape with rounded anterior and posterior extremities. Polar capsules are two, equal, broadly pyriform with a blunt anterior and a rounded posterior end measuring 4.8×1.8μm in size. A prominent tubular structure originate from the anterior end of one of the polar capsule and extend backward beyond the margin of the spore body and run upwards to join the posterior end of the other polar capsule.

Two new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida) infecting Indian freshwater fishes in Punjab Wetlands (India)

A survey of parasites of freshwater fishes in Harike and Ropar Wetlands of Punjab (India) revealed the presence of two new myxosporean species belonging to the genus Myxobolus Butschli 1882. Spores of the first species, M. duodenalis sp. nov. parasitize the inner wall of the duodenum of Wallago attu (Bloch and Schneider) (Cypriniformis: Cyprinidae) vern. mulli are characterized by a broad, pyriform shape with a blunt anterior end and measures 9.0 × 3.20 μm. Spore valves are thin, smooth, and symmetrical with no parietal folds. There are two polar capsules, prominently unequal and pyriform in shape, with a narrow anterior end and a rounded posterior end. The larger polar capsule measures 4.70 × 1.76 μm and the smaller 2.76 × 1.06 μm. The larger polar capsule occupies more than half, while the smaller one occupies one third of the spore body cavity. An intercapsular process is absent. Spores of the second species, Myxobolus patialensis sp. nov. parasitize the caudal fin of Labeo rohita (Ham. 1822) (Cypriniformis: Cyprinidae) vern. rohu are pyriform in valvular view, measuring 11.28 × 6.67 μm. The two shell valves are asymmetrical and contain five parietal folds along the posterior end of the spore. Two anteriorly situated polar capsules, elongated and oval in shape are prominently unequal in size. The larger polar capsule measures 4.8 × 3.1 μm and smaller one 1.70 × 1.51 μm. The larger polar capsule lies obliquely to the spore axis and the smaller one is at the same level but pointing outward anteriolaterally. An intercapsular process is absent. This species is characterized by having a prominent ridge on the shell surface anteriolaterally on the side of the smaller polar capsule.

A New Species of Myxosporean (Sphaeromyxidae), a Parasite of Lined Seahorses, Hippocampus erectus, from the Gulf of Mexico

Sphaeromyxa cannolii sp. n. is described from the bile ducts of aquaria-maintained lined seahorses (Hippocampus erectus) from the Gulf of Mexico. Spores of the new species are linear, 17-18 µm long and 5-6 µm wide, with flattened tips; polar capsules measure 4 × 3 µm. Routine necropsies of H. erectus following planned death revealed liver inflammation, bile duct obstruction, bile accumulation, and myxozoan parasites in the bile ducts of 11 of 40 animals sampled (27.5%). The presence of S. cannolii in an aquaculture setting should prompt keepers to carefully quarantine new animals and exclude annelid fauna, a potential intermediate host of myxozoans.

Myxobolus sp. (Myxozoa) in the circulating blood of Colossoma macropomum (Osteichthyes, Characidae)

Myxosporea parasitize many organs in fresh and saltwater fish. Species of the genus Myxobolus parasitizing the gills and other organs of the tambaqui Colossoma macropomum have been described. In the present study, blood smears were made from juvenile tambaqui and were stained with May Grunwald-Giemsa-Wright in order to identify myxozoan parasites. Out of a total of 36 fish examined, one specimen (2.7%) that was reared in a cage presented spores that were identified as M. colossomatis, whereas fish kept in 250 L tanks showed prevalence of 5.5%. This is the first report of M. colossomatis in the blood of farmed tambaqui in the Amazon region. These results indicate that myxozoan parasites should also be investigated in fish blood smears. Some myxosporean species may cause diseases in fish, and these species need to be identified so that adequate preventive sanitary control can be instituted.

Low host specificity in the Kudoidae (Myxosporea: Multivalvulida) including seventeen new host records for Kudoa thalassomi

Kudoid parasites are known to infect a large variety of fish. A significant proportion of Kudoa species have relatively low host specificity, with a single species able to infect multiple host species representing various host families even from different host orders. Since DNA sequences have been associated with myxosporean species characterisations, it has become far easier to determine host range of new species and validate host records from earlier descriptions. This study investigated the host specificity of a kudoid parasite, Kudoa thalassomi Adlard, Bryant, Whipps et Kent, 2005, from the Great Barrier Reef in Australia using DNA sequence analysis and morphology. The results revealed the host specificity to be broad, with K. thalassomi identified in 18 different fish species representing six different fish families. This study also compares current genetic information from different host isolates of Kudoa Meglitsch, 1947 to their host ranges recorded in existing literature. From this analysis, only half of the Kudoa species with multiple host records (27 Kudoa species) have half or more isolates that are genetically characterised, and thus specifically identified with a high confidence, from their known hosts. Only five kudoid species have genetically characterised isolates from all of their recorded hosts.

Two New Families and a New Species of Myxosporeans (Myxozoa, Myxosporea) of the Mediterranean and Black Sea Fishes

Two New Families and a New Species of Myxosporeans (Myxozoa, Myxosporea) of the Mediterranean and Black Sea FishesDescriptions of two new families — Polysporoplasmidae fam. n. (Syn. Sphaerosporidae Davis, 1917 in Sitja-Bobadilla, Alvarez-Pellitero, 1995) and Gadimyxidae fam. n. (syn. Parvicapsulidae Schulman, 1953 in Kie et al., 2007), and one new species of myxosporeans —Gadimyxa ovalesp. n. — parasites of fishes of the Mediterranean and the Black Seas are presented. Species of the genus Gadimyxa is found for the first time in the Black Sea.

Myxobolus supamattayai n. sp. (Myxosporea: Myxobolidae) from Thailand parasitizing the scale pellicle of wild mullet (Valamugil seheli)

A new myxosporean species, Myxobolus supamattayai n. sp., was isolated from wild mullet (Valamugil seheli) from the Andaman Sea, Thailand and described based on its morphology and molecular data. The myxosporean produced black plasmodia-like unique clinical sign on the skin with sporogonic stages and mature spores. Polysporous plasmodia, up to 2.5 mm in diameter, were found in epithelium tissue in the scale pocket. The spores measured 6.6 (6.2-7.0) μm in length, 6.5 (6.2-6.7) μm in width, smooth, and round board to ellipsoidal in valvular view. Spores were enclosed with intracapsular process which represents 5-7 and 11-12 in amount revealed in light microscopy and ultrastructure, respectively. The polar capsules were pyriform and of equal size, measuring 3.5 (3.4-3.6) μm in length and 2.0 (1.9-2.2) μm in width, with four to five turns of polar filament arranged perpendicularly to longitudinal axis of the polar capsule. In conclusion, this new species is entirely different from those previously described; however, this finding was assured by the partial sequence of SSU rRNA gene (1,666 bp) analysis that differed from all known species of Myxobolus Bütschli, 1882. The phylogenetic tree of the sequence data sets including those of freshwater and marine of Myxobolus spp. and the sister group (Henneguya spp.) was constructed to establish the relationship of this new species in Myxobolus clade and to explore its relations between their sister groups. Phylogenetic analysis indicated that a monophyletic group with Myxobolus spp. which infected mullet represents the newly formed species. These results suggested the presumably nearby evolution prospecting of Myxobolus species that were found in the same host.

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

A new myxosporean species, Henneguya eirasi n. sp., is described parasitizing the gill filaments of Pseudoplatystoma corruscans and Pseudoplatystoma fasciatum (Siluriformes: Pimelodidae) caught in the Patanal Wetland of the state of Mato Grosso, Brazil. The parasite formed white, elongated plasmodia measuring up to 3 mm. Mature spores were ellipsoidal in the frontal view, measuring 37.1 ± 1.8 μm in total length, 12.9 ± 0.8 μm in body length, 3.4 ± 0.3 μm in width, 3.1 ± 0.1 μm in thickness and 24.6 ± 2.2 μm in the caudal process. Polar capsules were elongated and equal in size, measuring 5.4 ± 0.5 μm in length and 0.7 ± 0.1 μm in width. Polar filaments had 12–13 coils. Histopathological analysis revealed that the parasite developed in the sub-epithelial connective tissue of the gill filaments and the plasmodia were surrounded by a capsule of host connective tissue. The plasmodia caused slight compression of the adjacent tissues, but no inflammatory response was observed in the infection site. Ultrastructure analysis revealed a single plasmodial wall connected to the ectoplasmic zone through numerous pinocytotic canals. The plasmodial wall exhibited numerous projections and slightly electron-dense material was found in the ectoplasm next to the plasmodial wall, forming a line just below the wall. Partial sequencing of the 18S rDNA gene of H. eirasi n. sp. obtained from P. fasciatum resulted in a total of 1066 bp and this sequence did not match any of the Myxozoa available in the GenBank. Phylogenetic analysis revealed the Henneguya species clustering into clades following the order and family of the host fishes. H. eirasi n. sp. clustered alone in one clade, which was the basal unit for the clade composed of Henneguya species parasites of siluriform ictalurids. The prevalence of the parasite was 17.1% in both fish species examined. Parasite prevalence was not influenced by season, host sex or host size.

Myxidium finnmarchicum n. sp. (Myxosporea: Myxidiidae) from the gall bladder of whiting Merlangius merlangus (L.) (Pisces: Teleostei) in North Norway

A new species of myxosporean is described from the gall bladder of whiting Merlangius merlangus (L.) (Pisces: Teleostei) caught at the northernmost extremity of the range of this fish off the northwest coast of Finnmark county, North Norway. The new species, Myxidium finnmarchicum, is described morphologically and genetically and compared with other similar species of Myxidium reported from the gall bladders of gadid fish in the North Atlantic - M. sphaericum, M. gadi and M. bergense. Both the morphological and molecular descriptions support the status of Myxidium finnmarchicum as a new species. Myxidium sphaericum is a parasite of whiting in the North Sea, but the two species are separated geographically by an intervening area in the northern North Sea north of 58° N where no whiting has been found infected with any species of Myxidium. Based upon 18S rRNA analysis, M. finnmarchicum shows closest sequence identity to M. gadi. The confusion in the literature regarding the validity and host specificities of M. sphaericum, M. gadi, M. bergense and M. incurvatum is highlighted and discussed. We suggest that a more detailed investigation of the range of morphological and molecular variation in these parasites from their various reported host species is required.

Kudoa iwatai and two novel Kudoa spp., K. trachuri n. sp. and K. thunni n. sp. (Myxosporea: Multivalvulida), from daily consumed marine fish in western Japan

Infection of marine fish by certain myxosporean species of the genus Kudoa results in unsightly cyst formation in the trunk muscle or post-mortem myoliquefaction, causing a great economic loss to aquaculture industries, capture fisheries, and fish dealers. In addition, consumers encountering unsightly Kudoa cysts in fish fillets believe them to be unknown foreign materials acquired during processing. To identify prevalent Kudoa spp. encountered in daily life by the Japanese population, fresh fish slices (sashimi) or fish fillets with whitish spots were collected during a 7-month period (May to December 2008) at local markets in the city of Yamaguchi, western Japan. Kudoa cysts were found in three Japanese seaperches (Lateolabrax japonicus), two black sea bream (Acanthopagrus schlegelii), two Japanese jack mackerel (Trachurus japonicus), and one albacore (Thunnus alalunga). Kudoa iwatai was identified in all the examined Japanese seaperch and black sea bream from Japan's Inland Sea, as assessed by morphology and genetic analysis of the 18S and 28S ribosomal RNA gene (rDNA). Kudoa trachuri n. sp. from two Japanese jack mackerel fished in the Japanese Sea off Nagasaki and Kudoa thunni n. sp. from one albacore fished in the Pacific Ocean had a spore, which was semiquadrate in shape in apical views and ovoid in lateral views, with four equal shell valves and drop-like polar capsules. Scanning electron microscopy revealed that these three Kudoa species had different types of small projections at the apex of each valve. The 18S and 28S rDNA sequences of K. trachuri n. sp. and K. thunni n. sp. were found to be closely related to those of Kudoa crumena; however, these sequences were distinct in each of the species, which additionally exhibited different morphological features.