Myzozoa is a grouping of specific phyla within Alveolata, that either feed through myzocytosis, or were ancestrally capable of feeding through myzocytosis. Many protozoan orders are included within Myzozoa. It is sometimes described as a phylum, containing the major subphyla Dinozoa and

Apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. Th ...

, plus minor subphyla. The term Myzozoa superseded the previous term "Miozoa", by the same authority, and gave a slightly altered meaning.

Phyla

Within Myzozoa, there are around four phyla: *

– parasitic protozoa that lack axonemal locomotive structures except in

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s *

Dinoflagellate The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s – mostly marine

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and thei ...

s many of which have

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it i ...

s *

Chromerida Chromerida is a phylum of unicellular alveolates, which includes photosynthetic species '' Chromera velia'' and '' Vitrella brassicaformis''. General features of the phylum include spherical cells each with a thick cell wall, chloroplast present w ...

– a marine phylum of photosynthetic protozoa *

Perkinsozoa Perkinsozoa is a proposed phylum of intracellular parasites in the superphylum Alveolata, which was suggested to account for the genus '' Perkinsus'' and other protist A protist () is any eukaryotic organism (that is, an organism whose cell ...

The term/group Myzozoa was not considered in a resolution of protist groups by Adl et al. 2012. Strict taxonomy only considers common traits possessed by all organisms of the group. Some organisms within each of the component groups of Myzozoa have lost the ability for Myzocytosis. Further, as taxonomy pays no account of molecular phylogeny, one current classification has all alveolate taxa other than apicomplexans, ciliates and dinoflagellates, named under the grab bag term "Protalveolata". The difficulty of placing very early dinozoans either within or outside the group "dinoflagellates" continues to favour classifications such as Protalveolata, as does the potential polyphyly between the two genera of "colpodellids"

Voromonas ''Voromonas'' is a genus of predatory alveolates. The genus and species were described by Mylnikov in 2000. It was originally described as ''Colpodella pontica'' but was later renamed by Cavalier-Smith and Chao in 2004. Taxonomy There is one ...

and

Colpodella ''Colpodella'' is a genus of alveolates comprising 5 species, and two further possible species: They share all the synapomorphies of apicomplexans, but are free-living, rather than parasitic. Many members of this genus were previously assigned to ...

Evolution

The most closely related large clade to the myzozoans are the

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a differen ...

s. Both of these groups of organisms – unlike the majority of eukaryotes studied to date – seem to have a linear mitochondrial genome. Most other eukaryotes that have had their mitochondrial genomes examined have circular genomes. However, the taxonomic term Myzozoa specifically excludes

s which are rather under the higher taxonomic rank Alveolata. Thus, Alveoata includes two large groups: Myzozoa and Ciliophora plus the smaller groups discussed above. All Myzozoa appears to have evolved from an ancestor that possessed plastids, required through endosymbiosis. The branching order within both Myzozoa and Protalveolata, is only partly understood. Three groups – the Colpodellids, Chromerida and the Apicomplexa – appear to be sister clades. Three other groups – the Perkinsids, Syndiniales and Oxyrrhis are distantly related to the dinoflagellates.

Notes

Perkinsus marinus ''Perkinsus marinus'' is a species of alveolates belonging to the phylum Perkinsozoa.Joseph, S., et al. (2010)The alveolate ''Perkinsus marinus'': biological insights from EST gene discovery.''BMC Genomics'' 11(1), 228. It is similar to a dinofl ...

'' and the

both have

histone In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn a ...

s while the

dinoflagellate The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s appear to have lost theirs.

are ancestrally myzocytotic, on the basis of evidence for myzocytosis by the chromerid ''Vitrella brassicaformis''.

References

{{Taxonbar, from1=Q1096964, from2=Q21447667 Alveolate taxonomy