Myxozoans: Ancient metazoan parasites find a home in phylum Cnidaria.

Myxozoans are endoparasites with complex life cycles that alternate between invertebrate and vertebrate hosts. Though considered protozoans for over 150 years, they are now recognized as metazoans, given their multicellularity and ultrastructural features. In recognition of synapomorphies and cnidarian-specific genes, myxozoans were placed recently within the phylum Cnidaria. Although they have lost genetic and structural complexity on the path to parasitism, myxozoans have retained characteristic cnidarian cnidocysts, but use them for initiating host infection. Myxozoans represent at least 20% of phylum Cnidaria, but as a result of rapid evolution, extensive diversification and host specialization, they are probably at least as diverse as their free-living relatives. The ability of myxozoans to infect freshwater, marine and terrestrial hosts implies that Cnidaria are no longer constrained to the aquatic environment.

[1]  M. Martindale,et al.  Functional roles of Notch signaling in the cnidarian Nematostella vectensis. , 2012, Developmental biology.

[2]  L. Tavares,et al.  Host-parasite-environment relationship, morphology and molecular analyses of Henneguya eirasi n. sp. parasite of two wild Pseudoplatystoma spp. in Pantanal Wetland, Brazil. , 2011, Veterinary parasitology.

[3]  B. Hausdorf,et al.  Agent of Whirling Disease Meets Orphan Worm: Phylogenomic Analyses Firmly Place Myxozoa in Cnidaria , 2013, PloS one.

[4]  J. Bartholomew,et al.  Myxozoans Exploiting Homeotherms , 2015 .

[5]  H. Hartikainen,et al.  A novel minicollagen gene links cnidarians and myxozoans , 2011, Proceedings of the Royal Society B: Biological Sciences.

[6]  Nimrod D. Rubinstein,et al.  Diversity and evolution of myxozoan minicollagens and nematogalectins , 2014, BMC Evolutionary Biology.

[7]  L. Margolis,et al.  THE DEMISE OF A CLASS OF PROTISTS : TAXONOMIC AND NOMENCLATURAL REVISIONS PROPOSED FOR THE PROTIST PHYLUM MYXOZOA GRASSE, 1970 , 1994 .

[8]  Nicholas H. Putnam,et al.  Sea Anemone Genome Reveals Ancestral Eumetazoan Gene Repertoire and Genomic Organization , 2007, Science.

[9]  S. Ponader,et al.  Myxozoan transmission via actinospores: new insights into mechanisms and adaptations for host invasion , 2007, Parasitology.

[10]  R. Yuste,et al.  Back to the Basics: Cnidarians Start to Fire , 2017, Trends in Neurosciences.

[11]  T. Bosch,et al.  Transgenic Stem Cells in Hydra Reveal an Early Evolutionary Origin for Key Elements Controlling Self-renewal and Differentiation , 2007 .

[12]  A. Collins,et al.  Phylogenetic placement of the enigmatic parasite, Polypodium hydriforme, within the Phylum Cnidaria , 2008, BMC Evolutionary Biology.

[13]  J. Lom,et al.  Myxozoan genera: definition and notes on taxonomy, life-cycle terminology and pathogenic species. , 2006, Folia parasitologica.

[14]  Zhi-qiang Zhang.  Animal biodiversity: An update of classification and diversity in 2013. In : Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013) , 2013 .

[15]  K Wolf,et al.  Biology Contravenes Taxonomy in the Myxozoa: New Discoveries Show Alternation of Invertebrate and Vertebrate Hosts , 1984, Science.

[16]  Meng Wang,et al.  The Genome of the Myxosporean Thelohanellus kitauei Shows Adaptations to Nutrient Acquisition within Its Fish Host , 2014, Genome biology and evolution.

[17]  A. Kuris,et al.  Independent origins of parasitism in Animalia , 2016, Biology Letters.

[18]  B. Okamura,et al.  Development and myogenesis of the vermiform Buddenbrockia (Myxozoa) and implications for cnidarian body plan evolution , 2012, EvoDevo.

[19]  Benjamin M. Wheeler,et al.  The dynamic genome of Hydra , 2010, Nature.

[20]  J. Bartholomew,et al.  Myxozoan parasitism in waterfowl. , 2008, International journal for parasitology.

[21]  E. Wagner,et al.  Comparison of Discharge Mechanisms of Cnidarian Cnidae and Myxozoan Polar Capsules , 2003 .

[22]  Nimrod D. Rubinstein,et al.  Genomic insights into the evolutionary origin of Myxozoa within Cnidaria , 2015, Proceedings of the National Academy of Sciences.

[23]  L. Smith,et al.  Molecular evidence that the myxozoan protists are metazoans. , 1994, Science.

[24]  S. Atkinson,et al.  Myxozoans on the Move: Dispersal Modes, Exotic Species and Emerging Diseases , 2015 .

[25]  H. Hartikainen,et al.  Assessing myxozoan presence and diversity using environmental DNA. , 2016, International journal for parasitology.

[26]  H. Hartikainen,et al.  Adaptive Radiation and Evolution Within the Myxozoa , 2015 .

[27]  J. Khattra,et al.  Recent Advances in Our Knowledge of the Myxozoa , 2001, The Journal of eukaryotic microbiology.

[28]  E. Canning,et al.  A New Class and Order of Myxozoans to Accommodate Parasites of Bryozoans with Ultrastructural Observations on Tetracapsula bryosalmonae (PKX Organism) , 2000, The Journal of eukaryotic microbiology.

[29]  U. Shavit,et al.  Myxozoan polar tubules display structural and functional variation , 2016, Parasites & Vectors.

[30]  Sinwook Park,et al.  Functional and proteomic analysis of Ceratonova shasta (Cnidaria: Myxozoa) polar capsules reveals adaptations to parasitism , 2017, Scientific Reports.

[31]  A. Fujiyama,et al.  Using the Acropora digitifera genome to understand coral responses to environmental change , 2011, Nature.

[32]  M. Siddall,et al.  The demise of a phylum of protists: phylogeny of Myxozoa and other parasitic cnidaria. , 1995, The Journal of parasitology.

[33]  F. Rentzsch,et al.  Evolution of eumetazoan nervous systems: insights from cnidarians , 2015, Philosophical Transactions of the Royal Society B: Biological Sciences.

[34]  E. Raikova.  Life cycle, cytology, and morphology of Polypodium hydriforme, a coelenterate parasite of the eggs of acipenseriform fishes. , 1994, The Journal of parasitology.

[35]  J. Lom,et al.  The first finding of myxosporean development from plasmodia to spores in terrestrial mammals: Soricimyxum fegati gen. et sp. n. (Myxozoa) from Sorex araneus (Soricomorpha). , 2007, Folia parasitologica.

[36]  A. Holzer,et al.  The joint evolution of the Myxozoa and their alternate hosts: A cnidarian recipe for success and vast biodiversity , 2018, Molecular ecology.

[37]  F. G. Wallace,et al.  A newly revised classification of the protozoa. , 1980, The Journal of protozoology.

[38]  P. Holland,et al.  Buddenbrockia Is a Cnidarian Worm , 2007, Science.

[39]  A. Böttger,et al.  The Notch signaling pathway in the cnidarian Hydra. , 2007, Developmental biology.