Opalinata is a superclass of non- phagotrophic heterokonts that unites the classes Opalinea and Blastocystea, and is the sister group to Opalomonadea.

Description

When Opalinata was first erected as a taxon in 1926, it was placed as the sole class in the group "Protociliata" and considered as primitive cilliates due to the fact that they move thanks to their numerous

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

and that they both present two nuclei. They were distinguished because they perform syngamy by the complete fusion of uninucleated gametes, while the rest of ciliates, forming "Euciliata" ( Ciliata + Suctoria), perform syngamy through their micronuclei alone while their macronuclei dissolve.
The taxon Opalinata was revised in 1996 by Cavalier-Smith and placed in

Opalozoa Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista. Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic saprot ...

, and is now defined by the following

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

: gut parasitism and the loss of

peroxisomes A peroxisome () is a membrane-bound organelle, a type of microbody, found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen pe ...

and

phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis i ...

Phylogeny

The cladogram below shows the relationships between Opalinata and the rest of

Classification

The modern taxonomy of Opalinata is as follows: * Phylum

Bigyra Bigyra is a grouping of heterokont organisms. It includes Bicosoecida, Blastocystis and Labyrinthulida. It has also been described as containing Opalozoa, Bicoecia, and Sagenista. Phylogeny The cladogram below shows the internal relationships wi ...

** Subphylum

Cavalier-Smith, 1991 stat. n. 2006 em. *** Infraphylum Placidozoa Cavalier-Smith 2013 **** Superclass Opalinata Wenyon, 1926 em. Cavalier-Smith, 1996 stat. n. 2006 ***** Class Opalinea Wenyon, 1926 stat. n. Cavalier-Smith, 1993 em. 2013 ****** Order Proteromonadida Grassé, 1952 em. Cavalier-Smith, 1993 ******* Family Proteromonadidae Grassé, 1952 ('' Proteromonas'') ****** Order

Opalinida The opalines are a small group of peculiar heterokonts, currently assigned to the family Opalinidae, in the order Slopalinida. Their name is derived from the opalescent appearance of these microscopic organisms when illuminated with full sunlig ...

Poche, 1913 stat. n. Hall, 1953 em. Cavalier-Smith ******* Family Karotomorphidae Travis, 1934 ('' Karotomorpha'') ******* Family Opalinidae Claus, 1874 (e.g. '' Cepedea'', ''

Protoopalina ''Protoopalina'' is a genus of heterokonts. Examples are '' Protoopalina intestinalis'' and '' Protoopalina pingi''. Species listed by the Australian Faunal Directory The Australian Faunal Directory (AFD) is an online catalogue of taxonomic an ...

'', '' Opalina'') ***** Class Blastocystea Zierdt et al., 1967 ****** Order Blastocystida Zierdt, 1978 ******* Family

Blastocystidae ''Blastocystis'' is a genus of single-celled heterokont parasites belonging to a group of organisms that are known as the Stramenopiles (also called Heterokonts) that includes algae, diatoms, and water molds. Blastocystis consists of severa ...

Jiang and He, 1988 (type genus '' Blastocystis'' Aléxéieff, 1911)

References

{{Taxonbar, from=Q2024928 Placidozoa