Phylogenetic relationships amongst Chloromyxum Mingazzini, 1890 (Myxozoa: Myxosporea), and the description of six novel species from Australian elasmobranchs
ABSTRACT Six novel species of Chloromyxum Mingazzini, 1890 are described using a whole evidence approach combining morphometric and molecular data, together with features of their biology. Elasmobranchs were collected in Australian waters, from the Great Barrier Reef, Queensland, off Lizard and Heron Islands; from Moreton Bay, southeast Queensland; off Hobart, Tasmania; and from the Tamar River, Launceston, Tasmania. The novel species proposed here are: Chloromyxum hemiscyllii n.sp. from Hemiscyllium ocellatum; Chloromyxum kuhlii n.sp. from Neotrygon kuhlii; Chloromyxum lesteri n.sp. from Cephaloscyllium laticeps; Chloromyxum mingazzinii n.sp. from Pristiophorus nudipinnis; Chloromyxum myliobati n.sp. from Myliobatis australis; and Chloromyxum squali n.sp. from Squalus acanthias. A seventh species from Squalus acanthias is also reported but due to limited material is not formally described. Molecular phylogenetic analyses revealed that the genus Chloromyxum is polyphyletic, and species from elasmobranchs form a well-supported sister clade, with the type species Chloromyxum leydigi, to all other congeneric species clustering within the freshwater myxosporean clade. Morphological analysis showed that elasmobranch-infecting species are predominantly pyriform shaped, have clearly thickened spore apex and possess caudal filaments, compared to other Chloromyxum species which are generally spherical or subspherical, and lack caudal filaments. These morphological and phylogenetic data provide further support for the erection of new genera, but we conservatively consider the species described in this study and other elasmobranch-infecting Chloromyxum species as Chloromyxum sensu strictu, whilst the freshwater teleost infecting and amphibian infecting species we will assign as Chloromyxum sensu lato, until more comprehensive data are available.
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ABSTRACT: Myxosporea (Myxozoa), a group of parasitic Cnidaria, use mostly bony fishes (Teleostei) as intermediate hosts; however, they can also parasitize other vertebrates such as cartilaginous fish (Chondrichthyes). Molecular data of myxosporeans from sharks and rays (Elasmobranchii) revealed these parasites to be one of the most basal representatives in the myxosporean phylogenetic tree, suggesting their ancient evolutionary history. A new myxosporean species, Bipteria vetusta n. sp., was found in the gall bladder of rabbit fish, Chimaera monstrosa (Holocephali; Chondrichthyes), and ssrDNA-based phylogeny revealed its basal position within the marine myxosporean lineage. Molecular dating based on ssrDNA analysis suggested the origin of a stem lineage leading to the marine myxosporean lineage at the time of the origin of Chondrichthyes in the Silurian era. The two common lineages of Myxozoa, Myxosporea and Malacosporea, were estimated to have split from their common ancestor in the Cambrian era. Tracing the history of evolution of the "vertebrate host type" character in the context of molecular dating showed that cartilaginous fish represented an ancestral state for all myxosporeans. Teleosts were very likely subsequently parasitized by myxozoans four times, independently. Myxosporean radiation and diversification appear to correlate with intermediate host evolution. The first intermediate hosts of myxosporeans were cartilaginous fish. When bony fish evolved and radiated, myxosporeans switched and adapted to bony fish, and subsequently greatly diversified in this new host niche. We believe that the present study is the first attempt at molecular dating of myxozoan evolution based on an old myxosporean species - a living myxosporean fossil. Copyright © 2015. Published by Elsevier Ltd.International Journal for Parasitology 02/2015; 63(4). DOI:10.1016/j.ijpara.2014.12.004 · 3.40 Impact Factor
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ABSTRACT: SUMMARY Myxosporeans are among the most common parasites of marine fish. Their economic importance is mainly as pathogens of both wild and farmed fish, but they have also been used as biological tags in population studies of their fish hosts. Here we review the literature and show the distribution of different families of Myxosporea infecting marine fishes in the world's oceans - the North Atlantic, South Atlantic, North Pacific, South Pacific and Indian. We also analyse their distribution in different orders of marine fishes. New families, genera and species of marine Myxosporea are continually being described and many more await description. Some regions, in particular the North Atlantic, have been more thoroughly investigated than others, so the analyses we present may not reflect the true distributions and we acknowledge that these may change considerably as other regions are investigated more fully. The distribution of myxosporean families in different taxonomic groups of marine fishes can indicate phylogenetic relationships between parasite and host and suggest the origins of different myxosporean taxa. We present some examples, while recognizing that new molecular information on phylogenetic relationships within the Myxozoa will lead to major changes in classification.Parasitology 09/2014; 141(13):1-9. DOI:10.1017/S0031182014001425 · 2.35 Impact Factor
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ABSTRACT: In order to clarify the phylogenetic relationships among the main marine myxosporean clades including newly established Ceratonova clade and scrutinizing their evolutionary origins, we performed large-scale phylogenetic analysis of all myxosporean species from the marine myxosporean lineage based on three gene analyses and statistical topology tests. Furthermore, we obtained new molecular data for Ceratonova shasta, C. gasterostea, eight Ceratomyxa species and one Myxodavisia species. We described five new species: Ceratomyxa ayami n. sp., C. leatherjacketi n. sp., C. synaphobranchi n. sp., C. verudaensis n. sp. and Myxodavisia bulani n. sp.; two of these formed a new, basal Ceratomyxa subclade. We identified that the Ceratomyxa clade is basal to all other marine myxosporean lineages, and Kudoa with Enteromyxum are the most recently branching clades. Topologies were least stable at the nodes connecting the marine urinary clade, the marine gall bladder clade and the Ceratonova clade. Bayesian inference analysis of SSU rDNA and the statistical tree topology tests suggested that Ceratonova is closely related to the Enteromyxum and Kudoa clades, which represent a large group of histozoic species. A close relationship between Ceratomyxa and Ceratonova was not supported, despite their similar myxospore morphologies. Overall, the site of sporulation in the vertebrate host is a more accurate predictor of phylogenetic relationships than the morphology of the myxospore. Copyright © 2015 Elsevier Inc. All rights reserved.Molecular Phylogenetics and Evolution 03/2015; DOI:10.1016/j.ympev.2015.03.004 · 4.02 Impact Factor