Myzozoa

Not to be confused with Myxozoa.

Myzozoa^[1] is a grouping of specific phyla within Alveolata,^[2][3] that either feed through myzocytosis, or were ancestrally capable of feeding through myzocytosis.^[1]

Myzozoa
Myzozoa membrane structure
Scientific classification
Domain:	Eukaryota
Clade:	Sar
Clade:	Alveolata
Clade:	Myzozoa Cavalier-Smith & Chao 2004
Phyla
Apicomplexa Chromerida Dinozoa Dinoflagellata Perkinsozoa

It is sometimes described as a phylum, containing the major subphyla Dinozoa and Apicomplexa, plus minor subphyla.^[4]

The term Myzozoa superseded the previous term Miozoa, by the same authority, and gave a slightly altered meaning.^[1]

Phyla

Within Myzozoa, there are four phyla:

• Apicomplexa – parasitic protozoa that lack axonemal locomotive structures except in gametes
• Dinoflagellata – mostly marine flagellates many of which have chloroplasts
• Chromerida – a marine phylum of photosynthetic protozoa
• Perkinsozoa

Evolution

The most closely related large clade to the myzozoans are the ciliates.^[1] 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 ciliates^[1] which are rather under the higher taxonomic rank Alveolata. Thus, Alveoata includes two large groups: Myzozoa and Ciliophora^[5] plus the smaller groups discussed above.

All Myzozoa appears to have evolved from an ancestor that possessed plastids, required through endosymbiosis.^[6]

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.^[7] Three other groups – the Perkinsids, Syndiniales and Oxyrrhis are distantly related to the dinoflagellates.^[8][9]

Notes

Perkinsus marinus and the Apicomplexa both have histones while the dinoflagellates appear to have lost theirs.^[10]

Chromerida are ancestrally myzocytotic, on the basis of evidence for myzocytosis by the chromerid Vitrella brassicaformis.^[11]