Explore the vast range of titles available.

Background Phylogenetic relationships among myxosporeans based on ribosomal DNA data disagree with traditional taxonomic classification: a number of myxosporeans with very similar spore morphology are assigned to the same genera even though they are phylogenetically distantly related. The credibility of rDNA as a suitable marker for Myxozoa is uncertain and needs to be proved. Furthermore, we need to know the history of myxospore evolution to understand the great diversity of modern species. Results Phylogenetic analysis of elongation factor 2 supports the ribosomal DNA-based reconstruction of myxozoan evolution. We propose that SSU rDNA is a reliable marker for inferring myxozoan relationships, even though SSU rDNA analysis markedly disagrees with the current taxonomy. The analyses of character evolution of 15 morphological and 5 bionomical characters show the evolution of individual characters and uncover the main evolutionary changes in the myxosporean spore morphology and bionomy. Most bionomical and several morphological characters were found to be congruent with the phylogeny. The summary of character analyses leads to the simulation of myxozoan ancestral morphotypes and their evolution to the current species. As such, the ancestor of all myxozoans appears to have infected the renal tubules of freshwater fish, was sphaerosporid in shape, and had a spore with polar capsules that discharged slightly sideways. After the separation of Malacosporea, the spore of the common myxosporean ancestor then changed to the typical sphaerosporid morphotype. This species inhabited the marine environment as a parasite of the gall bladder of marine fish and ultimately separated into the three main myxosporean lineages evident today. Two of these lineages re-entered the freshwater environment, one as a myxosporean with Chloromyxum and another with a primitive sphaerosporid morphotype. The common ancestor of all marine myxosporeans had a ceratomyxid shape of spore. Conclusions We support rDNA based myxozoan phylogeny by the analysis of a protein coding gene and demonstrate the reliability of rDNA as a marker explaining myxozoan relationships. Our tracing the history of myxozoan character evolution discloses ancestral morphotypes and shows their development over the course of evolution. We point out several myxozoan characters that are to a certain extent congruent with the phylogeny and determined that the discrepancy between phylogeny and current taxonomy based on spore morphology is due to an extreme myxospore plasticity occurring during myxozoan evolution.

Background The myxosporean Myxidium giardi Cépède, 1906 was described infecting the kidney of the European eel, Anguilla anguilla (L.), having spindle-shaped myxospores and terminal sub-spherical polar capsules. Since then, numerous anguillid eels globally have been documented to have similar Myxidium infections. Many of these have been identified using the morphological features of myxospores or by the location of infection in the host, and some have been subsequently synonymised with M. giardi . Therefore, it is not clear whether M. giardi is a widely distributed parasite, infecting numerous species of eels, in multiple organs, or whether some infections represent other, morphologically similar but different species of myxosporeans. The aim of the present study was to assess the status of M. giardi infections in Icelandic eels, and related fish hosts in Malaysia and to use spore morphology and molecular techniques to evaluate the diversity of myxosporeans present. Results The morphologies of the myxospores from Icelandic eels were very similar but the overall dimensions were significantly different from the various tissue locations. Myxospores from the kidney of the Malaysian tarpon, Megalops cyprinoides (Broussonet), were noticeably smaller. However, the SSU rDNA sequences from the different tissues locations in eels, were all very distinct, with percentage similarities ranging from 92.93% to as low as 89.8%, with the sequence from Malaysia being even more dissimilar. Molecular phylogenies consistently placed these sequences together in a clade that we refer to as the Paramyxidium clade that is strongly associated with the Myxidium clade ( sensu stricto ). We erect the genus Paramyxidium n. g. (Myxidiidae) to accommodate these histozoic taxa, and transfer Myxidium giardi as Paramyxidium giardi Cépède, 1906 n. comb. as the type-species. Conclusions There is not a single species of Myxidium ( M. giardi ) causing systemic infections in eels in Iceland. There are three species, confirmed with a robust phylogeny, one of which represents Paramyxidium giardi n. comb. Additional species probably exist that infect different tissues in the eel and the site of infection in the host fish is an important diagnostic feature for this group ( Paramyxidium n. g. clade). Myxospore morphology is generally conserved in the Paramyxidium clade, although actual spore dimensions can vary between some species. Paramyxidium spp. are currently only known to infect fishes from the Elopomorpha.

Two myxozoan species were observed in the kidney of topsmelt, Atherinops affinis, during a survey of parasites of estuarine fishes in the Carpinteria Salt Marsh Reserve, California. Fish collected on 3 dates in 2012 and 2013 were sectioned and examined histologically. Large extrasporogonic stages occurred in the renal interstitium of several fish from the first 2 collections (5/8, 11/20, respectively) and, in some fish, these replaced over 80% of the kidney. In addition, presporogonic and polysporogonic stages occurred in the lumen of the renal tubules, collecting ducts, and mesonephric ducts. The latter contained subspherical spores with up to 4 polar capsules, consistent with the genus Chloromyxum. For the third collection (15 May 2013, n = 30), we portioned kidneys for examination by histology, wet mount, and DNA extraction for small subunit ribosomal (SSU rDNA) gene sequencing. Histology showed the large extrasporogonic forms in the kidney interstitium of 3 fish and showed 2 other fish with subspherical myxospores in the lumen of the renal tubules with smooth valves and 2 spherical polar capsules consistent with the genus Sphaerospora. Chloromyxum-type myxospores were observed in the renal tubules of 1 fish by wet mount. Sequencing of the kidney tissue from this fish yielded a partial SSU rDNA sequence of 1,769 base pairs (bp). Phylogenetic reconstruction suggested this organism to be a novel species of Chloromyxum, most similar to Chloromyxum careni (84% similarity). In addition, subspherical myxospores with smooth valves and 2 spherical polar capsules consistent with the genus Sphaerospora were observed in wet mounts of 2 fish. Sequencing of the kidney tissue from 1 fish yielded a partial SSU rDNA sequence of 1,937 bp. Phylogenetic reconstruction suggests this organism to be a novel species of Sphaerospora most closely related to Sphaerospora epinepheli (93%). We conclude that these organisms represent novel species of the genera Chloromyxum and Sphaerospora based on host, location, and SSU rDNA sequence. We further conclude that the formation of large, histozoic extrasporogonic stages in the renal interstitium represents developmental stages of Chloromyxum species for the following reasons: (1) Large extrasporogonic stages were only observed in fish with Chloromyxum-type spores developing within the renal tubules, (2) a DNA sequence consistent with the Chloromyxum sp. was only detected in fish with the large extrasporogonic stages, and (3) several Sphaerospora species have extrasporogonic forms, but they are considerably smaller and are composed of far fewer cells.

During a survey on the myxosporean fauna of Rajiformes from the Atlantic coast of Argentina, in waters off Buenos Aires Province (34°–42°S; 53°–62°W), the gall bladders of 217 specimens belonging to seven species of skates, representatives of two families, were examined. As a result, three species of Chloromyxum Mingazzini, 1890, namely C. atlantoraji n. sp., C. zearaji n. sp. and C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo and Matos, 2009 were found infecting three endemic host species, the spotback skate Atlantoraja castelnaui (Arhynchobatidae), the yellownose skate Zearaja chilensis (Rajidae) and the Rio skate Rioraja agassizii (Arhynchobatidae), respectively. These species were described based on myxospore morphology and morphometry characterization, as well as by providing their small subunit ribosomal DNA (SSU rDNA) sequences. The SSU rDNA-based phylogenetic analyses showed that these three species constituted a well-established monophyletic subclade within the marine Chloromyxum clade, while branches subtending the other Chloromyxum species were poorly resolved or unresolved, independently of the host taxonomic identities (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes and Torpediniformes) and/or host geographic distribution (Atlantic coast of Portugal, Atlantic coast of the USA, Australian waters or Mediterranean Sea). The possible causes of these discrepancies are discussed, providing new insights into the phylogeny of the marine Chloromyxum clade. Lors d’une étude de la faune des Myxozoaires des Rajiformes de la côte atlantique argentine, dans les eaux situées au large de la province de Buenos Aires (34°–42°S; 53°–62°O), les vésicules biliaires de 217 spécimens appartenant à sept espèces, représentants deux familles, ont été examinés. En conséquence, trois espèces de Chloromyxum Mingazzini, 1890, à savoir C. atlantoraji n. sp., C. zearaji n. sp. et C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo et Matos, 2009 ont été trouvées, infectant trois espèces hôtes endémiques, Atlantoraja castelnaui (Arhynchobatidae), Zearaja chilensis (Rajidae) et Rioraja agassizii (Arhynchobatidae), respectivement. Ces espèces sont décrites sur la base de la morphologie et de la morphométrie des myxospores, ainsi qu’en fournissant leurs petites séquences d’ADN ribosomal (SSU ADNr). Les analyses phylogénétiques basées sur l’ADNr SSU ont montré que ces trois espèces constituaient un sous-clade monophylétique bien établi dans le clade des Chloromyxum marins, tandis que les branches sous-jacentes aux autres espèces de Chloromyxum étaient mal ou non résolues, indépendamment des identités taxonomiques hôtes (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes et Torpediniformes) et/ou de la répartition géographique de l’hôte (côte atlantique du Portugal, côte atlantique des États-Unis, eaux australiennes ou mer Méditerranée). Les causes possibles de ces divergences sont discutées, fournissant de nouvelles informations sur la phylogénie du clade des Chloromyxum marins.

BACKGROUND: Approximately 40 species of Sphaeromyxa have been described, all of which are coelozoic parasites from gall bladders of marine fish. They are unique amongst the myxosporeans as they have polar filaments that are flat and folded instead of being tubular and spirally wound. This unusual feature was used as a subordinal character to erect the suborder Sphaeromyxina, which contains one family, the Sphaeromyxidae, and a single genus Sphaeromyxa. METHODS: In the present study, we examine eelpout from the genus Lycodes from Iceland for the presence of myxosporean parasites in the gall bladder and perform morphological and DNA studies. RESULTS: A novel myxosporean, Sphaeromyxa lycodi n. sp., was identified in the gall bladders of five of the six species of Lycodes examined, with a prevalence ranging from 29 - 100%. The coelozoic plasmodia are large, polysporous and contain disporic pansporoblasts and mature spores which are arcuate. The pyriform polar capsules encase long and irregularly folded ribbon-like polar filaments. Each spore valve has two distinct ends and an almost 180° twist along the relatively indistinct suture line. The single sporoplasm is granular with two nuclei. Sphaeromyxa lycodi is phylogenetically related to other arcuate sphaeromyxids and is reproducibly placed with all known sphaeromyxids and forms part of a robustly supported clade of numerous myxosporean genera which infect the hepatic biliary systems of a wide range of hosts. CONCLUSIONS: Sphaeromyxa lycodi is a common gall bladder myxosporean in eelpout of the genus Lycodes from Northern Iceland. It has characteristics typical of the genus and develops arcuate spores. Molecular phylogenetic analyses confirm that sphaeromyxids form a monophyletic group, subdivided into straight and arcuate spore forms, within the hepatic biliary clade that infect a wide range of freshwater associated animals. The ancestral spore form for the hepatic biliary clade was probably a Chloromyxum morphotype; however, sphaeromyxids have more recently evolved from an ancestor with a spindle-shaped Myxidium spore form. We recommend that the suborder Sphaeromyxina is suppressed; however, we retain the family Sphaeromyxidae and place it in the suborder Variisporina.

A synopsis of the species of Chloromyxum Mingazinni, 1890 (Myxozoa: Myxosporea: Chloromyxidae) is presented, including 140 nominal species. For each species the most relevant morphological and morphometric characteristics are indicated. Included are data on the site of infection within the host, the original host and the host locality, plus a full bibliography of the original records for these species. A diagrammatic illustration of a spore of each species is also provided.

Microscopic and molecular procedures are used to describe a new myxosporean species, Chloromyxum clavatum n. sp., infecting the cartilaginous fish Raja clavata Linnaeus, 1758 (Chondrichthyes: Rajidae), collected from the northwest Atlantic coast of Portugal. Young plasmodia and mature spores were found floating free in the gall bladder of R. clavata. Spores were spherical to subspherical with a pointed anterior end, measuring14.4 ± 0.5 μm (n = 25) in length, 11.9 ± 0.5 μm (n = 25) in width, and 9.4 ± 0.5 μm (n = 15) in thickness. The spore's wall was composed of 2 equally sized valves, each displaying 6–8 elevated surface ridges and a bundle of several tapering caudal filaments attached to the basal portion. Spores contained 4 pyriform equally sized polar capsules (5.5 ± 0.4 μm × 2.9 ± 0.5 μm) (n = 25), each possessing an obliquely arranged isofilar polar filament coiled in 7–8 coils. Morphological data, host specificity, tissue tropism, and molecular analysis of the SSU rDNA gene identify this parasite as a new species of Chloromyxum. Neighbor-joining and maximum likelihood further reveal the parasite clustering with other species of Chloromyxum infecting the gall bladder of marine cartilaginous fish to form a clade positioned at the base of the freshwater clade, therefore constituting an exception to the major division of the class Myxosporea into the freshwater and marine clades, while supporting the existence of a correlation between tissue tropism and myxosporean phylogeny.

We are conducting studies on the impacts of parasites on Oregon coastal coho salmon (Oncorhynchus kistuch). An essential first step is documenting the geographic distribution of infections, which may be accomplished by using different methods for parasite detection. Thus, the objectives of the current study were to (1) identify parasite species infecting these stocks of coho salmon and document their prevalence, density, and geographic distribution; (2) assess the pathology of these infections; and (3) for the first time, determine the sensitivity and specificity of histology for detecting parasites compared with examining wet preparations for muscle and gill infections. We examined 576 fry, parr, and smolt coho salmon in total by histology. The muscle and gills of 219 of these fish also were examined by wet preparation. Fish were collected from 10 different locations in 2006–2007. We identified 21 different species of parasites in these fish. Some parasites, such as Nanophyetus salmincola and Myxobolus insidiosus, were common across all fish life stages from most basins. Other parasites, such as Apophallus sp., were more common in underyearling fish than smolts and had a more restricted geographic distribution. Additional parasites commonly observed were as follows: Sanguinicola sp., Trichodina truttae, Epistylis sp., Capriniana piscium, and unidentified metacercariae in gills; Myxobolus sp. in brain; Myxidium salvelini and Chloromyxum majori in kidney; Pseudocapillaria salvelini and adult digenean spp. in the intestine. Only a few parasites, such as the unidentified gill metacercariae, elicted overt pathologic changes. Histology had generally poor sensitivity for detecting parasites; however, it had relatively good specificity. We recommend using both methods for studies or monitoring programs requiring a comprehensive assessment of parasite identification, enumeration, and parasite-related pathology.

Parasitological research of two landlocked populations of Dolly Varden ( Salvelinus malma ) dwelling the river–lake system in the Uzon caldera (Kamchatka) was done for the first time. Twelve species of fresh-water parasites were found. Charrs from the Lake Tsentral’noe–Shumnaya River were infected by Eubothrium salvelini , Diphyllobothrium ditremum , D. dendriticum , Crepidostomum farionis , Cr. metoecus , Ichthyocotylurus erraticus , Sterliadochona ephemeridarum , Philonema oncorhynchi , and Cucullanus truttae . Charrs from the Lake Dal’nee were infected by Henneguya zschokkei , Chloromyxum coregoni , Proteocephalus longicollis , and Cucullanus truttae . Based on stomachs content and parasites abundance, it was found that charrs from the Lake Dal’nee feed on plankton, and at length more than 12 cm, switch to cannibalism. In the contrast, charrs from the Lake Tsentral’noe and Shumnaya River primarily feed on benthos and rarely on plankton, and no cannibalistic specimens were found.

Five myxozoan species, Tetracapsuloides bryosalmonae, Sphaerospora truttae, Chloromyxum schurovi, Chloromyxum truttae and a Myxobolus species were detected in farmed brown trout, Salmo trutta L. from Central Scotland. Using PCR and in situ hybridization, this study investigated the seasonal occurrence and tissue location of these species in young of the year brown trout. C. schurovi, C. truttae and Myxobolus sp. were first detected in brown trout in April, 2 months before T. bryosalmonae and S. truttae. T. bryosalmonae and S. truttae showed proliferation in the blood with intravascular stages of T. bryosalmonae accumulating in the heart. In contrast, only small amounts of PCR products of C. schurovi and C. truttae were obtained from the blood, suggesting that these species use the vascular system for transport but proliferate only in their target tissues from which large amounts of PCR product were obtained and where parasites were visible in histological sections. Large amounts of PCR product were obtained for T. bryosalmonae, S. truttae and both Chloromyxum species from the gills of brown trout, suggesting the gills as entry locus for these species. The neurotropic Myxobolus species formed plasmodia predominantly in the peripheral nerves, possibly indicating an entry route through the skin. Presporogonic stages of all other species had disappeared by September and mature spores were present from August onwards.