First report of a Kudoa lutjanus outbreak in farmed Chicken Grunts Parapristipoma trilineatum.

OBJECTIVE: As part of the National Disease Surveillance Program for Taiwanese Aquaculture, we investigated the causative agent of disease outbreaks in farmed Chicken Grunts Parapristipoma trilineatum. METHODS: In this study, outbreak cases on two separate farms were noticed in coastal Pingtung County, Taiwan. In total, 50 juvenile fish showing clinical signs (such as emaciation and erratic swimming behavior) and broodstock (two females and two males) from both farms were collected to perform gross lesion assessment, histopathological examination, and molecular identification of the pathogen. RESULT: Clinical symptoms were infected fish exhibited erratic swimming behavior, such as whirling and floating on the surface of the water. In the following months, cumulative mortality had reached 19% and 24%, respectively. The gross lesions in the infected fish included white oval cysts in the muscle, serosa of the internal organs, sclera of the eyes, and cerebral meninges. After conducting a wet mount examination of cysts using a light microscope, we observed a significant quantity of spores with morphological characteristics, suggesting their affiliation with the Myxosporea group. The spores were semiquadrate, with four tiny suture notches at the periphery; the mean spore length was 7.3 µm (SD = 0.5), and the mean spore width was 8.2 µm (SD = 0.6). The mean length and width of the pyriform polar capsules (nematocysts) were 3.6 µm (SD = 0.5) and 2.2 µm (SD = 0.5), respectively. The 18S and 28S ribosomal RNA sequences of these specimens were identical to those of Kudoa lutjanus. CONCLUSION: As this was the first time an outbreak of K. lutjanus in Chicken Grunts was confirmed, its reappearance with substantial mortality should serve as a warning to the aquaculture industry.

Kudoa hypoepicardialis and associated cardiac lesions in invasive red lionfish Pterois volitans in Grenada, West Indies.

Invasive red lionfish Pterois volitans (Linnaeus, 1758) represent an ongoing ecological threat within temperate and tropical waters. Relatively little is known regarding the overall health of P. volitans and their potential for spreading pathogens in non-native regions. Lionfish collected from inshore reefs of Grenada, West Indies, in 2019 and 2021 were identified as P. volitans based on cytochrome c oxidase subunit 1 barcoding. Gross and microscopic examination of tissues revealed myxozoan plasmodia in the hearts of 24/76 (31.6%) lionfish by histopathology or wet mount cytology. Further histopathologic examination revealed severe granulomatous inflammation and myofiber necrosis associated with developing plasmodia and presporogonic life stages. Fresh myxospores were morphologically and molecularly consistent with Kudoa hypoepicardialis, being quadrate in apical view with 4 valves and 4 equal polar capsules. The spore body was 5.1-7.9 (mean: 6.0) µm long, 8.1-9.8 (8.7) µm wide, and 6.9-8.5 (7.7) µm thick. Polar capsules were 2.3-2.7 (2.5) µm long and 0.9-1.6 (1.3) µm wide. 18S small subunit rDNA sequences were 99.81-99.87% similar to sequence data from the original description of the species. Novel 28S large subunit rDNA and elongation factor 2 data, which did not match any previously reported species, were provided. This is the first account of a myxozoan parasite of P. volitans, a new host record and locality for K. hypoepicardialis, and one of few reports describing pathogen-associated lesions in invasive lionfish.

Increased prevalence and severity of Kudoa thyrsites (Cnidaria: Myxosporea) in Atlantic salmon Salmo salar exposed to deeper seawater.

Kudoa thyrsites is a myxozoan parasite of marine fish with a global distribution. In British Columbia (BC), Canada, severe infections are associated with an economically significant degradation of fillet quality in farmed Atlantic salmon. Exposures to naturally occurring actinospores at a coastal research laboratory were used to test the hypothesis that the prevalence and severity of K. thyrsites infections acquired by exposure of Atlantic salmon to seawater (SW) of various depths are not different. In Expt 1, fish were exposed to SW from 1, 7 or 13 m below the surface. Following exposure to deeper-sourced SW, the prevalence of K. thyrsites, determined from microscopic examination of muscle histology sections, was greater in all 4 trials and the severity of infection was greater in 2 trials. In Expt 2, infections were compared over time among salmon held in tanks supplied with deep-sourced SW (raw or UV-irradiated) or in a surface net-pen. The infection was observed in 35 of 40 fish sampled between 3 and 6 mo after tank exposure to raw SW. Coincidentally, the parasite was observed in 4 of 40 fish maintained in the net-pen. No consistent association of the parasite infection was observed with temperature; however, reduced salinity and solar radiation were not ruled out as factors which may reduce the risk of infection from surface SW. These findings require verification at commercial aquaculture sites in BC, as they will inform considerations related to farm siting and net-pen configuration.

Multivalvulidan myxosporeans from marine fishes in Nha Trang Bay, Vietnam, with descriptions of Kudoa igori n. sp. and Kudoa borimiri n. sp. from mullets.

In March and April 2018, we carried out a survey of myxosporean parasites in coastal fishes collected from Nha Trang Bay in Vietnam's East Sea. Of the 159 fish specimens, 18 fish species were represented, belonging to 10 families. In 8 host species, 7 myxosporean species were found, representing the genera Kudoa and Unicapsula. Two of these species were new to science: Kudoa igori n. sp. from the gallbladder of Longarm mullet Osteomugil cunnesius (Valenciennes, 1836) (prevalence 10%) and Kudoa borimiri n. sp. from skeletal muscles of Longarm mullet and Longfinned mullet Osteomugil perusii (Valenciennes, 1836) (prevalence 30% and 60%, respectively). Vegetative stages were not found. Spores of K. igori n. sp. were small, orbicular to quadrate in apical view, and with four equal valves. In lateral view, spores were shallowly ovoid with a slightly protruding anterior pole. The 4 polar capsules were slightly unequal sizes and were oriented toward the apex of the spore. Dimensions were as follows: spore length 4.56 ± 0.22 (4.18-4.56), thickness 4.42 ± 0.39 (3.55-5.13), width 5.74 ± 0.46 (4.66-6.50), length of biggest polar capsule 1.38 ± 0.14 (1.1-1.65), middle 1.28 ± 0.12 (1.03-1.53), smallest 1.13 ± 0.11 (0.94-1.30), width of biggest polar capsule 1.03 ± 0.14 (0.83-1.4), middle 0.92 ± 0.12 (0.76-1.08), smallest 0.74 ± 0.12 (0.55-0.94). Spores of K. borimiri n. sp. had four equal valves with slightly rounded ends and were quadrate in apical view. In lateral view, spores were broadly deltoid. Four equal-sized polar capsules opened at the apex of the spore. In O. cunnesius, spore dimensions were as follows: length 3.51 ± 0.15 (3.34-3.92), thickness 3.65 ± 0.38 (2.79-4.21), width 4.97 ± 0.37 (4.13-5.97), length of the polar capsules 1.23 ± 0.18 (0.99-1.57), width 0.88 ± 0.07 (0.70-1.00). Overlapping dimensions for K. borimiri n. sp. spores were also found in O. perusii. Other known myxozoan species we encountered were Kudoa thyrsites and Kudoa whippsi, which had not previously been reported from the East Sea and Vietnam. We also encountered Kudoa monodactyli, which had not previously been reported from Nha Trang Bay. In addition, we report 2 additional species, a Kudoa sp. and a Unicapsula sp., that were not attributable to previously described myxozoans and need further investigation to completely characterize.

New records of three commercial fish hosts for two Unicapsula spp. and Kudoa megacapsula (Myxozoa: Myxosporea: Multivalvulida).

Infections caused by multivalvulid myxosporeans belonging to genera Unicapsula and Kudoa (Cnidaria: Myxozoa) occasionally affect commercial marine fish species. Postmortem myoliquefaction caused by a variety of Kudoa spp., including K. thyrsites, and unsightly cyst or pseudocyst formation, caused by K. amamiensis, U. muscularis, and other kudoid species, negatively affect commercial values of fillets. However, multivalvulid infections are often latent and imperceptible in the market. Biodiversity, host range, and epidemiology remain to be explored. Here, myxosporean infection was detected in four commercial fish species from southern China, using morphological and molecular analyses. Three Unicapsula spp. (U. pyramidata in Nemipterus japonicus; U. pflugfelderi in Dentex angolensis transported from the Eastern Central Atlantic Ocean, off West African coast; and U. aequilobata in Decapterus macarellus) and Kudoa megacapsula in Nemipterus virgatus were observed to form pseudocysts in the myofibers of the host trunk muscles. All fish hosts identified here, except for U. pyramidata, are new records. Kudoa megacapsula was morphologically characterized by gigantic, cruciform myxospores with four wing-like shell valves morphologically comparable to previous Japanese records of the same species in aquaculture facilities, acquiring fly from China or Korea (Sphyraena pinguis and Seriola quinqueradiata, respectively). Molecular analyses established the conspecificity of the present Chinese isolate with previously recorded Japanese isolates. To our knowledge, for the first time, a partial large subunit ribosomal RNA gene sequence of K. megacapsula was obtained, showing close phylogenetic relationships with Kudoa spp. harboring cruciform myxospores, such as K. thyrsites, K. gunterae, K. whippsi, and K. lateolabracis.

Occurrence of Kudoa prunusi and K. lateolabracis (Myxozoa: Myxosporea: Multivalvulida) in Philippine-Sea Japanese parrotfish (Calotomus japonicus).

Multiple Kudoa spp. (Myxozoa: Myxosporea: Multivalvulida) have been recorded in Japanese parrotfish (Calotomus japonicus) from the Philippine Sea (Northwest Pacific Ocean), off southwestern Japan; Kudoa yasunagai in the brain, and K. igami, K. lateolabracis, and K. thalassomi in the muscles. This study examined eight Philippine Sea Japanese parrotfish samples collected in January and February 2019 and found K. prunusi in the brain (3-57 plasmodia/fish; average 17.9) and K. lateolabracis plasmodia in the trunk muscle of all fish individuals examined. The K. prunusi in this study was characterized by myxospores predominatetly with six shell valves (SVs) and a corresponding number of polar capsules (PCs), contrasting with the original description of the species from farmed Pacific bluefin tuna (Thunnus orientalis) brain that characterized the species as having predominately five SVs/PCs. Molecular-genetic characterization of 18S and 28S ribosomal RNA genes and mitochondrial DNA genes (cytochrome c oxidase subunit 1 and small and large ribosomal RNA subunits) clearly differentiated the K. prunusi isolate from K. yasunagai, commonly characterized by six or seven, but rarely five, SVs/PCs myxospores. The Japanese parrotfish is a new host record for K. prunusi and speculated to be an important reservoir host in its natural waters. Kudoa lateolabracis myxospores isolated from pseudocysts in the myofiber were morphologically and phylogenetically close to a clade of the Kudoa spp. that exhibit cruciform myxospores similar to K. thyrsites. This study is the first to sequence a mitochondrial DNA of small and large subunit ribosomal RNA of K. lateolabracis.

Morphometric and molecular characterization of Kudoa encrasicoli n. sp. (Myxozoa: Myxosporea) from the European anchovy, Engraulis encrasicolus (L.) (Clupeiformes: Engraulidae).

The European anchovy represents the main fisheries for countries in the Mediterranean and Black Sea basins. The skeletal muscle of 13 of 48 (27.1%) Engraulis encrasicolus (L.) specimens from North East Atlantic waters (FAO 27.8.c) was found infected with interfibrillar elongated plasmodia (130-980 µm in length) containing mature myxospores belonging to the genus Kudoa Meglitsch, 1947. No flesh softening was found associated with infection. Fresh myxospores were 10.8 ± 0.7 (9.1-12.3) µm in width 1, 11.3 ± 0.9 (9.5-13.4) µm in width 2, 6.7 ± 0.4 (5.8-7.4) µm in thickness, and 6.9 ± 0.5 (5.8-7.5) µm in length. They were almost stellate in apical view having three pointed-edged shell valves bearing three small polar capsules equal in size 5.0 ± 0.3 (4.4-5.4) µm long and 2.4 ± 0.2 (2.0-3.0) µm wide, and one rounded- to rarely bluntly pointed-edged shell valve bearing a large and particularly wide polar capsule 6.8 ± 0.4 (5.9-7.6) µm long and 4.1 ± 0.2 (3.6-4.4) µm wide. Morphological and morphometrical comparisons between these myxospores and those of Kudoa thyrsites (Gilchrist, 1923) from the clupeid Sardina pilchardus (Walbaum) (North East Atlantic waters, FAO 27.9.a), with which exhibited a similarity of 98.9% and 96.2% using SSU and LSU rDNA sequences, respectively, support the creation of Kudoa encrasicoli n. sp. Morphometrical analysis of the polar capsules of flattened myxospores is suggested as a useful approach to differentiate phylogenetically related kudoids with stellate or almost stellate myxospores bearing four polar capsules.

First report of three multivalvulid species (Cnidaria: Myxozoa: Myxosporea) in commercial fishes from Java Sea, Indonesia, with records of Unicapsula pyramidata and two new Kudoa spp.

Commercial marine fishes caught locally in East Java, Indonesia, were examined for multivalvulid myxosporeans (Cnidaria: Myxozoa: Myxosporea). Plasmodia of Unicapsula pyramidata were detected in the trunk muscle of two fork-tailed threadfin breams (Nemipterus furcosus). Genetic comparisons of this sample to those collected in the Australian Coral Sea and South China Sea showed few nucleotide substitutions in the small subunit and large subunit ribosomal RNA gene (rDNA) with the species isolated in the Australian Coral Sea and South China Sea. Pseudocysts of two new Kudoa spp. with four shell valves and polar capsules were found in the trunk muscle of two shrimp scads Alepes djedaba and two flathead grey mullets Mugil cephalus. Kudoa javaensis n. sp. myxospores isolated from the shrimp scad were 5.1-7.2 (mean 6.2) µm thick, 6.2-7.9 (7.3) µm wide, and 4.6-6.3 (5.4) µm long, with polar capsules 1.9-2.5 (2.2) µm long and 1.1-1.4 (1.3) µm wide (n = 15). Kudoa surabayaensis n. sp. myxospores isolated from the flathead grey mullet were 5.8-6.7 (6.3) µm thick, 6.4-7.6 (6.9) µm wide, and 4.6-5.0 (4.7) µm long, with polar capsules 1.8-2.4 (2.1) µm long and 0.9-1.3 (1.1) µm wide (n = 25). These two Kudoa spp. showed critical differences in spore shapes (semiquadrate with unequal shell valves vs. equal shell valves), and absence vs. presence of uplifted shell valve termini. Nucleotide sequencing of rDNA supported the morphological differentiation of these two species. Furthermore, these two isolates were morphologically and phylogenetically distinct from any recorded Kudoa spp.

Myxozoan parasites vary in river herring according to life history stage and habitat.

Anadromous river herring have declined in many parts of their range, leading to fisheries management efforts to help repopulate this species by improving connectivity of rivers and restoring populations by fish transfers. With data lacking on parasites in these species, this study sought to better understand myxozoans across various life stages and habitats in river herring populations in New Jersey, USA. We compared fish from riverine habitats during early-life growth and adults returning to spawn, marine-phase fish, and landlocked Alewife populations. Three myxozoan species were identified in young-of-the-year (YOY) anadromous river herring, including Kudoa clupeidae in the skeletal musculature, Myxobolus mauriensis in the rib cartilage, and an uncharacterized coelozoic myxozoan within the lumen of mesonephric tubules. In YOY river herring, Blueback Herring were 2 times more likely to be infected by K. clupeidae than Alewife (p = 0.019) and in the Maurice River, fish were 4 times more likely to be infected with M. mauriensis than fish from Great Egg Harbor River (p = 0.000) and 11 times more likely than the Delaware River (p = 0.001). Spawning adult river herring were infected with a previously undescribed myxozoan parasite infecting the kidney. Sequencing the 18S rDNA indicated this species is closely related to Ortholinea species. Myxobolus mauriensis and the Ortholinea-like species were absent from marine-phase river herring indicating that infections were linked to river environments occurring during early-life growth and spawning, respectively. No myxozoans were present in landlocked Alewife, showing that similar infections occurring in rivers were absent in lake environments in the region.

Effects of Kudoa septempunctata infections in a human intestinal epithelial model (Caco-2): a DNA microarray study.

Kudoa septempunctata, a myxosporean parasite infecting the trunk muscles of olive flounder (Paralichthys olivaceus), is reported to cause food poisoning in humans. The molecular mechanisms underlying the toxicity of K. septempunctata spores remain largely unknown. In the present study, we examine the molecular basis of such toxicity using DNA microarray analysis of K. septempunctata-inoculated human colon adenocarcinoma cells (Caco-2). We observed that the transepithelial resistance of the K. septempunctata-inoculated Caco-2 cell monolayers decreased markedly. DNA microarray analysis revealed that the mRNA expression profiles of control and inoculated cells clearly differed. Inflammatory and bacteria-related pathways, such as interleukin-8 (IL-8) production and MAPK/NF-kappa B pathway, were enriched. The concentrations of IL-8 and serotonin (5-HT) were higher in inoculated cells than in controls. K. septempunctata invasion damages the human intestinal epithelium, causing increased production of IL-8 and 5-HT, which likely results in the vomiting associated with K. septempunctata invasion.Abbreviations: AP-1: activator protein 1; DAVID: Database for Annotation, Visualization and Integrated Discovery; ENS: enteric nervous system; FARMS: Factor Analysis for Robust Microarray Summarization; FDR: false discovery rate; GO: Gene Ontology; 5-HT: 5-hydroxytryptamine; IL-8: Interleukin-8; KEGG: Kyoto Encyclopedia of Genes and Genomes; K. septempunctata: Kudoa septempunctata; NF-kappa B: nuclear factor-kappa B; TJ: tight junction; TER: transepithelial electrical resistance.

Negative impact on the reproductive potential of blue jack mackerel Trachurus picturatus by Kudoa infection of the ovary.

Reproduction of Trachurus picturatus off the western Portuguese coast was studied over 1 yr. During histological analyses, the presence of Kudoa sp. was detected in advanced vitellogenic oocytes. Kudoa infections are known to cause economic loss through the induction of post-mortem liquefaction of fish muscles, but ovarian infection as reported in this study will seriously affect the reproductive potential of the species and thus impact fisheries productivity. Only females showed gonad infection which led to total degradation of advanced vitellogenic oocytes. No macroscopic, somatic or condition indices revealed differences between infected and uninfected females, rendering this infection event a concealed suppression of reproduction.

Identification of four new Kudoa spp. (Myxozoa: Myxosporea: Multivalvulida) in commercial fishes collected from South China Sea, Atlantic Ocean, and Bering Sea by integrated taxonomic approach.

Members of the myxosporean genus Kudoa are defined as having a myxospore with four or more shell valves (SVs) and a corresponding number of polar capsules (PCs). Here, we employed integrated taxonomic approaches to four kudoid isolates from Acentrogobius chlorostigmatoides and Konosirus punctatus from the South China Sea, off Guangdong, Pentanemus quinquarius from the Southeast Atlantic Ocean, off West African coast, and Atheresthes stomias from the Bering Sea, off Alaska, and concluded that all these kudoids were novel species, named Kudoa acentrogobia n. sp., Kudoa guangdongensis n. sp., Kudoa iidae n. sp., and Kudoa aburakarei n. sp., respectively. Kudoa guangdongensis n. sp., forming pseudocysts in the trunk muscle myofibers of K. punctatus, had large-sized tripod myxospores with three wing-like SV extensions and three PCs (one prominent PC and two rudimentary PCs). Phylogenetic analyses based on the 18S and 28S ribosomal RNA gene (rDNA) demonstrated its affinity to the genus Kudoa, not to Unicapsula characterized by a myxospore with one prominent PC and two rudimentary PCs, suggesting the atypical nature of this new species in the context of myxospore morphology. Three other kudoid isolates had four SVs and PCs in a semi-quadrated, ray-like, or cruciform myxospore, respectively, forming pseudocysts in the trunk muscle myofibers. Kudoa iidae n. sp. forming pseudocysts in the muscles of P. quinquarius from Southeast Atlantic Ocean had unique myxospores with ray-like form, showing close morphological resemblance to Kudoa rayformis, which were recorded from the muscle of Scomberomorus sierra from the Pacific Ocean off Panama. These two species had a phylogenetic relationship of morphological convergence, evolving separately in different sea areas. It is fairly difficult to differentiate K. acentrogobia n. sp. and K. aburakarei n. sp., prevalent in their host fishes, from kudoid species with similar myxospore morphology (e.g., Kudoa nova and Kudoa thyrsites, respectively), but distinct in phylogeny from known Kudoa spp. Combined taxonomic identification of multivalvulid myxosporeans based on both morphological criteria of isolated myxozoans and their molecular characterization could disclose their real biodiversity and phylogeny.

Phylogenetic relationships of three Kudoa spp. with morphologically similar myxospores (K. iwatai, K. lutjanus, and K. bora), with the redescription of K. uncinata and K. petala and description of a new species (K. fujitai n. sp.) in fishes in the South China Sea.

Members of the myxozoan genus Kudoa (Myxosporea: Multivalvulida: Kudoidae) are characterized as having four or more shell valves in a myxospore, with a corresponding number of polar capsules. Certain Kudoa spp. are critical pathogens in fish, causing postmortem myoliquefaction, unmarketable fish musculature due to unsightly macroscopic cysts, and reduced aquaculture production due to the outbreaks of neurological symptoms or cardiac diseases. Molecular genetic techniques have enabled the differentiation of Kudoa spp. with morphologically similar myxospores. In the present study, we employed integrated taxonomic approaches on five Kudoa spp. forming cysts between the trunk muscle myofibers (K. bora from Osteomugil perusii and K. lutjanus from Acanthopagrus latus), or cysts in the gallbladder wall (K. petala from Sillago sihama), and pseudocysts in the trunk muscle myofibers (K. uncinata from Nuchequula nuchalis and K. fujitai n. sp. from O. perusii). These four host fishes, which originated in the South China Sea, were purchased in the wet markets in Zhanjiang City, Guangdong Province, China, between August 2016 and April 2018. We have redescribed the four Kudoa spp. (K. bora, K. lutjanus, K. petala, and K. uncinata) on which little data are available after their original descriptions. Particularly, genetic characterization of K. bora and K. lutjanus, which are known to have myxospores morphologically similar to those of K. iwatai, was performed based on the nuclear ribosomal RNA gene and partial mitochondrial DNA genes such as cytochrome c oxidase subunit I and small and large ribosomal genes, demonstrating the validity and independence of these three kudoid species. We also provide description of a new species-K. fujitai n. sp.-in the present study. Application of integrated taxonomic approaches to known species characterized solely based on morphological criteria, as well as unknown species (e.g., K. fujitai n. sp. in the present study), contributes to better understanding of the biodiversity of Kudoa and multivalvulid myxosporeans.

Effect of Epigallocatechin Gallate on Viability of Kudoa septempunctata.

Kudoa septempunctata have been reported as a causative agent for acute transient gastrointestinal troubles after eating raw olive flounder (Paralichthys olivaceus). It raised public health concerns and quarantine control in several countries. Quantitative evaluation on viability of K. septempunctata is crucial to develop effective chemotherapeutics against it. A cytometry using fluorescent stains was employed to assess effect of three compounds on viability of K. septempunctata. Epigallocatechin gallate reduced markedly viability of K. septempunctata at 0.5 mM or more, and damaged K. septempunctata spores by producing cracks.

[Discovery of Putative Anti-Kudoa septempunctata Chemical Agents by Comprehensive Assay].

We screened 360 chemicals and discovered that 71 chemicals had anti-Kudoa septempunctata effect. Especially 19 and seven of 71 chemicals were antibiotics and antibacterial agents/disinfectants, respectively. The other 45 chemicals were pesticides, natural toxins, industrial chemicals and medicines for non-infectious diseases. Nineteen antibiotics that possessed anti-Kudoa effect contained four tetracyclines, one steroid, two macrolides, one aminoglycoside, three ß-lactams, one quinolone, two rifamycines, one polyene, one novobiocine, one sulfonamide and two nitroimidazoles. To use these drugs for prevention of Kudoa infection, the further study is need for the determination of effective dose.

Host size influences prevalence and severity of Kudoa thyrsites (Cnidaria: Myxosporea) infection in Atlantic salmon Salmo salar.

Kudoa thyrsites is a cosmopolitan myxozoan parasite of marine fish. The infection causes an economically important myoliquefaction in farmed Atlantic salmon in British Columbia, Canada. Laboratory exposure of Atlantic salmon smolts to infectious seawater was used to test the hypothesis that infection with K. thyrsites is more severe in age-matched, smaller salmon. In each of 2 trials approximately 4 mo apart, smolts were graded into small (80 and 68 g), medium (117 and 100 g) and large (142 and 157 g) initial weight groups (IWGs) and concurrently exposed to infectious seawater. The effects of IWG and time on fish size and infection severity were assessed by linear mixed-effects models. The fish were screened for infection by histological examination at intervals following exposure. Increases in mean length and weight were statistically significant in all IWG during both trials. The infection was detected in fish in both trials, and in Trial 2, the prevalence was significantly greater in larger fish 1000 degree-days (DD) after exposure. The severity of infection (plasmodia mm-2 muscle) was significantly higher in larger smolts: between medium and large IWGs at 2500 DD in Trial 1 and between small and medium IWGs at 1500 and 2000 DD in Trial 2. The hypothesis is rejected and possible explanations for the greater occurrence of K. thyrsites in larger smolts are discussed.

Morphological and molecular identification of a new Kudoa thyrsites isolate in Mediterranean silver scabbardfish Lepidopus caudatus.

Myxozoans of the genus Kudoa (Myxosporea, Multivalvulida) infect marine and estuarine fish species worldwide. Some Kudoa species are of concern to the seafood industry since they may generate macroscopic cysts in the fish host's musculature, or cause post mortem myoliquefaction, commonly known as 'soft flesh'. One of the economically most important species is K. thyrsites, a myoliquefactive myxosporean parasite that occurs in many wild and cultured marine fish species worldwide. Here we identified a K. thyrsites isolate as the causative agent of myoliquefaction in silver scabbardfish Lepidopus caudatus from the Alboran Sea (western Mediterranean Sea). For comparative and validation purposes, the morphological and molecular characteristics of the isolate were compared with fresh spores of a K. thyrsites isolate infecting Atlantic mackerel Scomber scombrus from the Norwegian Sea. Myxospores of both isolates shared a stellate appearance and contained 4 unequal pyriform polar capsules (1 large, 1 small and 2 intermediate). These morphological traits were consistent with all other previously described K. thyrsites isolates. Moreover, the small subunit rDNA sequences of the Mediterranean and Norwegian Sea isolates revealed 100% similarity, and matched 100% with K. thyrsites isolates previously recorded in myoliquefactive Atlantic mackerel from the North Sea and off southern England. The findings suggest that K. thyrsites is the primary cause of myoliquefaction in silver scabbardfish from the Alboran Sea. This report represents the first morphological and molecular characterization of K. thyrsites in the Mediterranean Sea. A set of new allometric characters is proposed as additional descriptors for more accurate and specific description of kudoid myxospores.

New host records of three Kudoa spp. (K. yasunagai, K. thalassomi, and K. igami) with notable variation in the number of shell valves and polar capsules in spores.

To date, 26 Kudoa spp. (Myxozoa: Myxosporea: Multivalvulida) have been recorded in edible marine fishes in Japan. In the future, it is likely that even more marine fish multivalvulid myxosporeans will be characterized morphologically and genetically, which will aid the precise understanding of their biodiversity and biology. We examined 60 individuals of six fish species collected from the Philippine Sea off Kochi or from the border between the Philippine Sea and East China Sea around Miyako Island, Okinawa, i.e., the southern part of Japan. Newly collected parasite species included Kudoa yasunagai from the brain of Japanese meagre (Argyrosomus japonicus) and Japanese parrotfish (Calotomus japonicus), Kudoa miyakoensis n. sp. and Kudoa thalassomi from the brain and trunk muscle, respectively, of bluespine unicornfish (Naso unicornis), and Kudoa igami from the trunk muscle of Carolines parrotfish (Calotomus carolinus), African coris (Coris gaimard), and Pastel ringwrasse (Hologymnosus doliatus). With the exception of Japanese parrotfish for K. yasunagai, all these fish are new host records for each kudoid species. Notable variation in the number of shell valves (SV) and polar capsules (PC) was observed for all four kudoid species. In particular, spores with seven or eight SV/PC were prominent in K. igami isolates, despite the original Japanese parrotfish-derived description characterizing it as having spores with six, or less commonly five, SV/PC. However, molecular genetic characterization based on the ribosomal RNA gene (rDNA) and mitochondrial DNA (cytochrome c oxidase subunit 1 and ribosomal RNA small and large subunits) found no significant differences in the nucleotide sequences of isolates with different phenotypical features as far as examined in the present study. A newly erected species, K. miyakoensis n. sp., was determined to be phylogenetically closest to brain-parasitizing species, such as K. chaetodoni, K. lemniscati, and K. yasunagai based on rDNA nucleotide sequences, but differed from them morphologically.

Kudoa sp. (Myxozoa, Multivalvulida): first report in five commercial fish species from the Canary Islands-FAO 34 (Macaronesia-Spain).

Kudoid myxozoans have been reported causing serious chronic problems in marine fisheries, by reducing the market value of infected fish through pathological damage to the host musculature. We report here the overall prevalence of a Kudoa species in 84/277 (30.3%) fishes from 20 different species of high commercial value captured between October 2011 and December 2013 from the United Nations Food and Agriculture Organization (FAO) 34 commercial fishing area, near the coast of the Canary Islands (Spain). Macroscopic examination showed myxozoan-like cysts in skeletal muscle from 5 of the 20 fish species examined, with the following prevalences: Pagellus acarne (86.7%), Pagellus erythrinus (46.5%), Serranus cabrilla (27.8%), Spondyliosoma cantharus (19.4%), and Sarpa salpa (28.6%). Infection intensity was determined based on spore counts following muscle tissue digestion. Morphometric studies to characterize the species and DNA sequence analysis results suggest that these infections are attributable to a Kudoa species closely related to Kudoa trachuri. This paper reports the first study on a multivalvulidan species to be identified from the Canary Islands. Furthermore, this is the first report of Kudoa parasites in all of the hosts mentioned above, with the exception of P. acarne.

Kudoa ogawai (Myxosporea: Kudoidae) Infection in Cultured Olive Flounder Paralichthys olivaceus.

Since Kudoa septempuntata was identified as a causative agent of food poisoning associated with raw olive flounder Paralichthys olivaceus, interest and concern regarding the parasite have increased. However, there have been no investigations or reports of other Kudoa species infecting the fish (except for K. paralichthys, which infects the brain) in Korea. We found cysts filled with myxospores of Kudoa species in muscles of cultured olive flounder specimens and identified these to the species level. Mature spores were quadrate, measuring 8.7±0.5 µm in length, 9.2±0.4 µm in thickness, and 12.9±0.6 µm in width. The spores containing 4 polar capsules had a length of 2.1±0.2 µm and a width of 1.8±0.3 µm. The partial 18S and 28S rDNA of isolates showed 99-100% similarities with K. ogawai. Using these morphological and molecular analyses, the species was identified as K. ogawai. This study is the first report of K. ogawai infection in cultured olive flounder in Korea.