The Myxozoa are a group of microscopic, parasitic animals. Originally taxonomists classed them as protozoa, and included them with other non-motile forms in the group Sporozoa. However, as their distinct nature became clear they gained their own phylum. Evolutionary theorists now generally consider them to have developed from multicellular animals, and classify them accordingly. A microscope (Greek: micron = small and scopos = aim) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria Acoelomorpha Orthonectida Rhombozoa Myxozoa Superphylum Deuterostomia Chordata (vertebrates, etc. ... Protozoa (in Greek protos = first and zoon = animal) are single-celled eukaryotes (organisms with nuclei) that show some characteristics usually associated with animals, most notably mobility and heterotrophy. ... Classes & subclasses Class Conoidasida    Gregarinasina    Coccidiasina Class Aconoidasida    Haemosporasina    Piroplasmasina The Apicomplexa are a large group of protozoa, characterized by the presence of an apical complex at some point in their life-cycle. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Subregnum Bilateria Acoelomorpha Orthonectida Rhombozoa Myxozoa Superphylum Deuterostomia Chordata (vertebrates, etc. ...

The Greek roots of the name myxozoa express the ideas of "slime" or "mucus" (myx-) and "animal" (zo-).

Many Myxozoa have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. Infection occurs by valved spores. These contain one or two sporoblast cells, and one or more polar capsules, containing filaments that 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. Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) A fish is a poikilothermic (cold-blooded) water-dwelling... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida (from Latin annellus little ring), are a large phylum of animals, comprising... Fossilized Bryozoa, Ordovician limestone, Batavia, Ohio Bryozoans (moss animals) are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. ... Species Plasmodium berghei Plasmodium brasilianum Plasmodium chabaudi Plasmodium cynomolgi Plasmodium falciparum Plasmodium gallinaceum Plasmodium knowlesi Plasmodium lophurae Plasmodium malariae Plasmodium ovale Plasmodium relictum Plasmodium vivax Plasmodium yoelii etc. ...

In structure and appearance the polar capsules closely resemble the stinging cells of Cnidaria. On account of this, biologists have generally regarded the Myxozoa as extremely reduced cnidarians, and in particular as close relatives of Polypodium, with some genetic support. More recent studies of Hox genes, however, point to an origin among the Bilateria. Strong support for this comes from the discovery that Buddenbrockia, a worm-like parasite of bryozoans up to 2 mm in length, belongs among the Myxozoa^[1]. Genetically difficult to distinguish from the other forms, it has Myxozoan-like spore capsules, but it retains a bilateral body form with longitudinal muscles. This serves as a missing link between the Myxozoa and their multicellular ancestors. Classes Anthozoa - Corals and sea anemones Cubozoa - Sea wasps or box jellyfish Hydrozoa - Hydroids, hydra-like animals Scyphozoa - Jellyfish Cnidaria (from New Latin cnida nematocyst, fr. ... Species See text Polypodium is a large genus of true ferns, widely distributed throughout the world, but specially developed in the tropics. ... A homeobox is a stretch of DNA sequence found in genes involved in the regulation of the development (morphogenesis) of animals, fungi and plants. ... Illustration of the different types of symmetry of Life Forms On Earth. ... Fossilized Bryozoa, Ordovician limestone, Batavia, Ohio Bryozoans (moss animals) are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. ... (If you intended to go to the record store Missing Link Records, click here ) Missing link is a term for a transitional form from the fossil record that connects an earlier species to a later one, or which connects two different species to an earlier ancestor. ...

Species

Some species of myxozoa include:

• Class Malacosporea
  • Buddenbrockia plumatellae
  • Tetracapsuloides bryosalmonae, an important salmon parasite
• Class Myxosporea
  • Myxobolus cerebralis, an important parasite of salmon and trout

Binomial name Tetracapsuloides bryosalmonae Canning , 1999 Synonyms Tetracapsuloides bryosalmonae is a myxosporean parasite of salmonid fishes, which causes Proliferative kidney disease (PKD), one of the most serious parasitic diseases of salmonid populations in Europe and North America[1], which causes losses of up to 90% in infected populations. ... The Chinook or King Salmon is the largest salmon in North America and can grow up to 58 long and 126 pounds. ... Orders Bivalvulida Multivalvulida The Myxosporea are a class of microscopic parasites, belonging to the phylum Myxozoa. ... Binomial name Myxobolus cerebralis Hofer, 1903 Synonyms Myxobolus cerebralis is a myxosporean parasite of salmonids (salmon, trout, and their allies) that causes whirling disease in farmed salmon and trout and also in wild fish populations. ... Rainbow trout (Oncorhynchus mykiss) Trout is the common name given to a number of species of freshwater fishes belonging to the salmon family, Salmonidae. ...

Taxonomic note

Taxonomists now recognize the outdated subgroup Actinosporea as a life-cycle phase of Myxosporea ^[2]. Orders Bivalvulida Multivalvulida The Myxosporea are a class of microscopic parasites, belonging to the phylum Myxozoa. ... A life cycle includes the major sexual stages of a species, especially in regard to its ploidy. ... Orders Bivalvulida Multivalvulida The Myxosporea are a class of microscopic parasites, belonging to the phylum Myxozoa. ...

Notes

• ^ 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.
• ^ Monteiro, A. S., Okamura, B., and P. W. H. Holland. "Orphan Worm Finds a Home: Buddenbrockia is a Myxozoan." Molecular Biology and Evolution 19:968-971 (2002)[3]