Sphaeromyxids form part of a diverse group of myxosporeans infecting the hepatic biliary systems of a wide range of host organisms

Kristmundsson, Árni; Freeman, Mark

doi:10.1186/1756-3305-6-51

Cited by 23 publications

(28 citation statements)

References 33 publications

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“…The type species of Myxidium , M. lieberkuehni is commonly found as coelozoic in the urinary system of the freshwater pike, Esox lucius , in the holarctic region of the northern hemisphere, it has elongated and striated myxospores with a sporoplasm containing two nuclei unlike those in the current description that have a single nucleus and smooth spore valves. In addition, M. lieberkuehni is robustly phylogenetically placed away from marine myxosporeans in a discrete clade with other coelozoic species infecting freshwater fishes [ 1 , 12 , 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…Tubes were then centrifuged at 1500g for 5 min, the supernatant removed and the pellet fixed in 2.5 % glutaraldehyde for 4h. After fixation, the spores were prepared for SEM and viewed following the methods described by Kristmundsson and Freeman [ 12 ]. In brief, washed spores were syringed onto a polycarbonate membrane, fixed with 1 % osmium tetroxide and dehydrated through an ethanol series.…”

Section: Methodsmentioning

confidence: 99%

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Histozoic myxosporeans infecting the stomach wall of elopiform fishes represent a novel lineage, the Gastromyxidae

Freeman

Kristmundsson

2015

Parasites Vectors

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BackgroundTraditional studies on myxosporeans have used myxospore morphology as the main criterion for identification and taxonomic classification, and it remains important as the fundamental diagnostic feature used to confirm myxosporean infections in fish and other vertebrate taxa. However, its use as the primary feature in systematics has led to numerous genera becoming polyphyletic in subsequent molecular phylogenetic analyses. It is now known that other features, such as the site and type of infection, can offer a higher degree of congruence with molecular data, albeit with its own inconsistencies, than basic myxospore morphology can reliably provide.MethodsHistozoic gastrointestinal myxosporeans from two elopiform fish from Malaysia, the Pacific tarpon Megalops cyprinoides and the ten pounder Elops machnata were identified and described using morphological, histological and molecular methodologies.ResultsThe myxospore morphology of both species corresponds to the generally accepted Myxidium morphotype, but both had a single nucleus in the sporoplasm and lacked valvular striations. In phylogenetic analyses they were robustly grouped in a discrete clade basal to myxosporeans, with similar shaped myxospores, described from gill monogeneans, which are located at the base of the multivalvulid clade. New genera Gastromyxum and Monomyxum are erected to accommodate these myxosporean taxa from fish and gill monogeneans respectively. Each are placed in a new family, the Gastromyxidae with Gastromyxum as the type genus and Monomyxidae with Monomyxum as the type genus.ConclusionsTo improve modern systematics of the myxosporeans it is clear that a combination of biological, ecological, morphological and molecular data should be used in descriptive studies, and the naming and redistribution of taxa and genera is going to be necessary to achieve this. Here we demonstrate why some Myxidium-shaped myxospores should not be included in the family Myxidiidae, and create two new families to accommodate them based on their site of infection, host biology / ecology, DNA sequence data and morphological observations. Subsequent descriptive works need to follow a similar course if we are going to create a prevailing and workable systematic structure for the Myxosporea.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Histozoic myxosporeans infecting the stomach wall of elopiform fishes represent a novel lineage, the Gastromyxidae

Freeman

Kristmundsson

2015

Parasites Vectors

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“…Microscopy X-cells were harvested from freshly caught cod by gentle mechanical disruption of the excised xenoma tissues using forceps. Released cells were fixed in 2.5% glutaraldehyde, passed through a 0.4mm Whatman Cyclopore track-etched polycarbonate membrane, and prepared for SEM [51]. In brief, membranes were post-fixed in 1% osmium tetroxide in 100 mM sodium cacodylate buffer pH 7.2 for 2hrs and taken through an ethanol series of 30%, 60%, 90% and 2 3 100% 30 min each, transferred into 50% hexamethyldisilazane (HMDS) in 100% ethanol followed by two changes of 100% HMDS each for 45 min.…”

Section: Star+methods Key Resources Tablementioning

confidence: 99%

X-Cells Are Globally Distributed, Genetically Divergent Fish Parasites Related to Perkinsids and Dinoflagellates

et al. 2017

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"X-cells" have long been associated with tumor-like formations (xenomas) in marine fish, including many of commercial interest. The name was first used to refer to the large polygonal cells that were found in epidermal xenomas from flatfish from the Pacific Northwest [1]. Similar looking cells from pseudobranchial xenomas had previously been reported from cod in the Atlantic [2] and Pacific Oceans [3]. X-cell pathologies have been reported from five teleost orders: Pleuronectiformes (flatfish), Perciformes (perch-like fish), Gadiformes (cods), Siluriformes (catfish), and Salmoniformes (salmonids). Various explanations have been elicited for their etiology, including being adenomas or adenocarcinomas [4, 5], virally transformed fish cells [6-8], or products of coastal pollution [9, 10]. It was hypothesized that X-cells were protozoan parasites [1, 11-13], and although recent molecular analyses have confirmed this, they have failed to place them in any phylum [14-18], demonstrating weak phylogenetic associations with the haplosporidians [16] or the alveolates [15]. Here, we sequenced rRNA genes from European and Japanese fish that are known to develop X-cell xenomas. We also generated a metagenomic sequence library from X-cell xenomas of blue whiting and Atlantic cod and assembled 63 X-cell protein-coding genes for a eukaryote-wide phylogenomic analysis. We show that X-cells group in two highly divergent clades, robustly sister to the bivalve parasite Perkinsus. We formally describe these as Gadixcellia and Xcellia and provide a phylogenetic context to catalyze future research. We also screened Atlantic cod populations for xenomas and residual pathologies and show that X-cell infections are more prevalent and widespread than previously known.

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“…Reinvasion of the marine environment has happened several times independently by taxa in this lineage. Kodádková et al (submitted) Examples include the large clade of typical marine Sphaeromyxa species (Kristmundsson and Freeman 2013), two marine Myxidium species (Fiala 2006;Kalavati et al 2013), several Myxobolus and Henneguya spp. from marine or brackish fish (e.g.…”

Section: Myxosporean Diversificationmentioning

confidence: 98%

Adaptive Radiation and Evolution Within the Myxozoa

Fiala

Bartošová-Sojková

Okamura

et al. 2015

Myxozoan Evolution, Ecology and Development

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Myxozoans are endoparasites characterized by extensive morphological simplification and complex life cycles. Their definitive hosts are bryozoans-in the case of the more primitive and species-poor Malacosporea, or annelids-in the case of the more derived and speciose Myxosporea. This chapter reviews patterns of adaptive radiation within the Myxozoa and explores the drivers that may have promoted evolutionary change. Topics covered include: multiple transitions between worm-like and sac-like forms in the Malacosporea; undersampling that likely limits our appreciation of malacosporean diversity; and multiple shifts between marine and freshwater environments in the Myxosporea. We also examine morphological simplification that is observed in stages that produce spores and associated changes in the size of these sporogonic stages. This contrasts with the evolution of morphological complexity in spores. Features proposed to be involved in diversification include the acquisition of hardened spores and plasmodia, a high diversity of definitive hosts and invasion of novel hosts and host environments in the

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Sphaeromyxids form part of a diverse group of myxosporeans infecting the hepatic biliary systems of a wide range of host organisms

Cited by 23 publications

References 33 publications

Histozoic myxosporeans infecting the stomach wall of elopiform fishes represent a novel lineage, the Gastromyxidae

Histozoic myxosporeans infecting the stomach wall of elopiform fishes represent a novel lineage, the Gastromyxidae

X-Cells Are Globally Distributed, Genetically Divergent Fish Parasites Related to Perkinsids and Dinoflagellates

Adaptive Radiation and Evolution Within the Myxozoa

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