Myzozoa is a grouping of specific phyla within Alveolata, that either feed through

myzocytosis Myzocytosis (from Greek: myzein, (') meaning "to suck" and kytos (') meaning "container", hence referring to "cell") is a method of feeding found in some heterotrophic organisms. It is also called "cellular vampirism" as the predatory cell pierce ...

, or were ancestrally capable of feeding through

. Many protist orders are included within Myzozoa. It is sometimes described as a phylum, containing the major subphyla Dinozoa and

Apicomplexa The Apicomplexa (also called Apicomplexia; single: apicomplexan) are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of non-photosynthetic plastid called an ap ...

, 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 The term Myzozoa superseded the previous term "Miozoa", by the same authority, and gave a slightly altered meaning.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 four phyla: *

– parasitic protozoa that lack axonemal locomotive structures except in

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s * Dinoflagellata – 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 the ...

s many of which have

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s *

Chromerida Chrompodellids are a phylum of single-celled protists belonging to the Alveolata supergroup. It comprises two different polyphyletic groups of flagellates: the colpodellids, phagotrophic predators, and the chromerids, photosynthetic algae t ...

– a marine phylum of photosynthetic protozoa * Perkinsozoa 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 A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies, which ar ...

between the two genera of "colpodellids" '' Voromonas'' and '' Colpodella''.

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 flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

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'' 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 and in most Archaeal phyla. They act as spools around which DNA winds to create structural units called nucleosomes ...

s while the

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

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 Alveolata taxa