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Myxozoa
Triactinomyxon stage of Myxobolus cerebralis.
Scientific classification
Kingdom: Animalia
(unranked): Radiata
Phylum: Cnidaria
Groups

Malacosporea
Myxosporea

The Myxozoa (etymology: Greek: myx- "slime" or "mucus" + zoa "animals") are a group of parasitic animals of aquatic environments. Over 1300 species have been described[1] and many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. The average size of a Myxosporea spore usually ranges from 10μm to 20μm [2] and Malacosporea up to 2mm. Infection occurs through valved spores. These contain one or two sporoblast cells and one or more polar capsules that contain filaments which anchor the spore to its host. The sporoblasts are then released as a motile form, called an amoebula, which penetrates the host tissues and develops into one or more multinucleate plasmodia. Certain nuclei later pair up, one engulfing another, to form new spores.

Contents

Phylogenetics

The Myxozoa were originally considered protozoan[3], and were included among other non-motile forms in the group Sporozoa[4]. As their distinct nature became clear through 18S ribosomal DNA (rDNA) sequencing, they were relocated in the metazoa. Further classification was hindered by conflicting evidence: although 18S rDNA suggested an affinity with Cnidaria,[5] other rDNA sampled,[6][7] and the HOX genes of two species,[8] were more similar to those of the Bilateria.

The discovery that Buddenbrockia plumatellae, a worm-like parasite up to 2 mm in length (relatively large), is a myxozoan[6] appeared to strengthen the case for a bilaterian origin, as the body plan is superficially similar. Nevertheless, closer examination reveals that Buddenbrockia is not longitudinally symmetrical by two ways, but four, casting doubt on this hypothesis.

Further testing has sourced the first three HOX genes found in previous research (Myx1-3) to the bryozoan Cristatella mucedo, and the fourth (Myx4) to Northern pike. This explained the confusion; original experiments had used contaminated tissue from host organisms, leading to false positives for a position among the Bilateria. More careful cloning of 50 coding genes from Buddenbrockia established the clade as severely modified members of the phylum Cnidaria, with medusozoans as their closest relatives. Similarities between myxozoan polar capsules and cnidarian nematocysts (stinging cells) had been drawn for a long time, but were generally assumed to be the result of convergent evolution (Still these are insufficient information).[9]

Taxonomists now recognize the outdated subgroup Actinosporea as a life-cycle phase of Myxosporea.[10]

Species

Some species of myxozoa include:

References

  1. ^ [1]
  2. ^ http://tolweb.org/Myxozoa/2460
  3. ^ Štolc, A. (1899). "Actinomyxidies, nouveau groupe de Mesozoaires parent des Myxosporidies". Bull. Int. L'Acad. Sci. Bohème 12: 1–12.  
  4. ^ Edwin Lanfranco, 2007, A phylogenetic classification of organisms other than animals.
  5. ^ Smothers, J.F., et al. (September 1994). "Molecular evidence that the myxozoan protists are metazoans". Science 265 (5179): 1719–1721. doi:10.1126/science.8085160. PMID 8085160.  
  6. ^ a b A.S. Monteiro, et al. (June 1, 2002). "Orphan worm finds a home: Buddenbrockia is a Myxozoan". Mol. Biol. Evol. 19 (6): 968. PMID 12032254. http://mbe.oxfordjournals.org/cgi/content/full/19/6/968.  
  7. ^ J. Zrzavy & V. Hypsa (April 2003). "Myxozoa, Polypodium, and the origin of the Bilateria: The phylogenetic position of "Endocnidozoa" in light of the rediscovery of Buddenbrockia". Cladistics 19 (2): 164. doi:10.1111/j.1096-0031.2003sampled+.tb00305.x.  
  8. ^ C. L. Anderson, E. U. Canning & B. Okamura (March 1999). "A triploblast origin for Myxozoa?". Nature 392 (6674): 346–347. doi:10.1038/32801.  
  9. ^ E. Jímenez-Guri, et al. (July 2007). "Buddenbrockia is a cnidarian worm". Science 317 (116): 116–118. doi:10.1126/science.1142024. PMID 17615357.  
  10. ^ Kent, M. L., Margolis, L. & Corliss, J.O. (1994). "The demise of a class of protists: taxonomic and nomenclatural revisions proposed for the protist phylum Myxozoa Grasse, 1970." Canadian Journal of Zoology 72(5):932-937.

External links

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Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Nuvola apps important.svg The status, affinity, scope or nomenclature of this taxon is disputed.

Please see discussion on the talk page.

Actinomyxon

Taxonavigation

Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: incertae sedis
Phylum: Myxozoa
Classes: Malacosporea - Myxosporea

Name

Myxozoa

References

  • Cairns, S.D.; Gershwin, L.-A.; Brook, F.J.; Pugh, P.; Dawson, E.W.; Ocaña V., O.; Vervoort, W.; Williams, G.; Watson, J.E.; Opresko, D.M.; Schuchert, P.; Hine, P.M.; Gordon, D.P.; Campbell, H.J.; Wright, A.J.; Sánchez, J.A.; Fautin, D.G. 2009: 4. Cnidaria: corals, medusae, hydroids, myxozoans. Pp. 59-101 in Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume 1. Kingdom Animalia. Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch, New Zealand.
  • Jiménez-Guri, E.; Philippe, H.; Okamura, B.; Holland, P.W.H. 2007: Buddenbrockia is a cnidarian worm. Science, 317: 116-118.
  • Kent, M.L.; Andree, K.B.; Bartholomew, J.L.; El-Matbouli, M.; Desser, S.S.; Devlin, R.H.; Feist, S.W.; Hedrick, R.P.; Hoffmann, R.W.; Khattra, J.; Hallett, S.L.; Lester, R.J.G.; Longshaw, M.; Palenzeula, O.; Siddall, M.E.; Xiao, C. 2001: Recent advances in our knowledge of the Myxozoa. Journal of eukaryotic microbiology, 48: 395-413.
  • Lom, J.; Dykova, I. 2006: Myxozoan genera: definition and notes on taxonomy, life-cycle terminology and pathogenic species. Folia parasitologica, 53(1): 1-36.
  • Monteiro, A.S.; Okamura, B.; Holland, P.W.H. 2002: Orphan worm finds a home: Buddenbrockia is a myxozoan. Molecular biology and evolution, 19: 968-971. [1]
  • Morris, D.J.; Adams, A. 2007: Sacculogenesis of Buddenbrockia plumatellae (Myxozoa) within the invertebrate host Plumatella repens (Bryozoa) with comments on the evolutionary relationships of the Myxozoa. International journal for parasitology, 37(10): 1163-1171.
  • Okamura, B.; Curry, A.; Wood, T.S.; Canning, E.U. 2002: Ultrastructure identifies Buddenbrockia as a myxozoan and reveals/identifies the bilaterian origin of the Myxozoa. Parasitology, 124: 215-223.
  • Xiao, C.; Desser, S.S. 2000: Cladistic analysis of myxozoan species with known alternating life-cycles. Systematic parasitology, 46: 81–91.
  • Zrzavý, J. 2001: The interrelationships of metazoan parasites: a review of phylum- and higher-level hypotheses from recent morphological and molecular phylogenetic analyses. Folia parasitologica, 48: 81-103.

links

Vernacular names

English: myxozoans
Português: Mixozoários

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