Apusozoa
Scientific classification
Domain:	Eukaryota
(unranked):	Bikonta
Phylum:	Apusozoa Cavalier-Smith 1997 em.
Orders
Apusomonadida Ancyromonadida Hemimastigida

The Apusozoa comprise several genera of flagellate protozoa. They are usually around 5-20 μm in size, and occur in soils and aquatic habitats, where they feed on bacteria. They are grouped together based on the presence of an organic shell or theca under the dorsal surface of the cell.

It has been described as a phylum.^[1]

Contents 1 Genera 2 Characteristics 3 Classification 4 References 5 Further reading

[edit] Genera

There are three orders, often treated as separate groups: the apusomonads, ancyromonads, and hemimastigids.

The apusomonads include two genera, Apusomonas and Amastigomonas, and the ancyromonads include one, Ancyromonas. They have two flagella inserted at right angles, near the anterior of the cell. They move by gliding, with one flagellum trailing along the side and one directed to the anterior.

The hemimastigids include three genera, Hemimastix, Spironema, and Stereonema. They are also called the spironemids or Hemimastigophora. Each cell has multiple flagella, arranged in rows from the anterior of the cell towards the posterior.

[edit] Characteristics

The form of the mitochondria varies between the different orders. Among the apusomonads they have tubular cristae, the ancyromonads flat cristae, and the hemimastigids ambiguous or sacculate cristae. This characteristic was originally considered a good indicator of relationships, but is now known to vary even among close relatives.

[edit] Classification

On molecular trees, the apusomonads and ancyromonads group together, but their relationship to other eukaryotes is uncertain.

Cavalier-Smith, in a collaborative paper with Alexandra Stechmann, postulated that Apusozoa belongs in the bikont clade.^[2][3]

Although it has sometimes been included in the Rhizaria, based on 18S rRNA gene sequencing, it has been concluded that the Apusozoa are not closely related to other Rhizaria.

It may be one of the most divergent bikont lineages.^[4]

It has also been suggested that it may be related to the opisthokont group.^[5]

[edit] References

[edit] Further reading

• Patterson DJ (October 1999). "The Diversity of Eukaryotes". Am. Nat. 154 (S4): S96–S124. doi:10.1086/303287. PMID 10527921. http://www.journals.uchicago.edu/cgi-bin/resolve?AN991002. 

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v • d • e Eukaryota classification Domain : Archaea - Bacteria - Eukaryota Bikonta AH/SAR AH Archaeplastida, or Plantae sensu lato Viridiplantae/Plantae sensu stricto · Rhodophyta  · Glaucocystophyceae Hacrobia, or non-SAR chromalveolata Haptophyta · Cryptophyta · Centroheliozoa SAR SA Heterokont ("S") Ochrophyta · Bigyra · Pseudofungi Alveolata Ciliates · Myzozoa (Apicomplexa, Dinoflagellata) Rhizaria Cercozoa · Retaria (Foraminifera, Radiolaria) Excavata Discoba (Euglenozoa, Percolozoa) · Metamonad · Malawimonas Apusozoa Apusomonadida (Apusomonas) · Ancyromonadida (Ancyromonas) · Hemimastigida (Hemimastix, Spironema, Stereonema) Unikonta Amoebozoa Lobosea · Conosa · Phalansterium Opisthokonta Holozoa Mesomycetozoea Dermocystida · Ichthyophonida Filozoa Filasterea Capsaspora · Ministeria Choanoflagellatea Codonosigidae Metazoa or "Animalia" Eumetazoa (Bilateria, Cnidaria, Ctenophora) · Mesozoa · Parazoa (Placozoa, Porifera) Fungi Dikarya (Ascomycota, Basidiomycota) · Glomeromycota · Zygomycota · Blastocladiomycota  · Chytridiomycota/Neocallimastigomycota  · Microsporidia sister: Nucleariidae (Nuclearia, Micronuclearia)