Opalinata is a superclass of non-

phagotrophic 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 is c ...

heterokonts Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, whi ...

that unites the classes

Opalinea 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 sunli ...

and

Blastocystea ''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 several ...

, and is the sister group to

Opalomonadea Opalomonadea is a class of biciliate phagotrophic opalozoans with an anterior hairy cilium, often from anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, ...

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 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 Suctoria are ciliates that become sessile in their developed stage and then lose their redundant cilia. They feed by extracellular digestion. They were originally thought to feed by suction – hence their name. In fact, they use specialize ...

), perform syngamy through their micronuclei alone while their macronuclei dissolve.
The taxon Opalinata was revised in 1996 by

Cavalier-Smith Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford. His research has led to disc ...

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 sapr ...

, and is now defined by the following synapomorphies: gut

parasitism Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

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 per ...

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 is ...

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 relationship ...

** Subphylum

Cavalier-Smith, 1991 stat. n. 2006 em. *** Infraphylum

Placidozoa Placidozoa is a recently defined non- photosynthetic lineage of Heterokonts. Phylogeny Taxonomy Infraphylum Placidozoa Cavalier-Smith 2013 * Superclass Wobblata Cavalier-Smith 2006 stat. n. 2013 ( paraphyletic) ** Class Placididea Moriya, Na ...

Cavalier-Smith 2013 **** Superclass Opalinata Wenyon, 1926 em. Cavalier-Smith, 1996 stat. n. 2006 ***** Class

Wenyon, 1926 stat. n. Cavalier-Smith, 1993 em. 2013 ****** Order

Proteromonadida Proteromonadidae is a paraphyletic family of heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the ...

Grassé, 1952 em. Cavalier-Smith, 1993 ******* Family

Proteromonadidae Proteromonadidae is a paraphyletic family of heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the ...

Grassé, 1952 (''

Proteromonas ''Proteromonas'' is a genus of heterokonts. It lives in the gut of amphibians and reptiles. An example is ''Proteromonas lacertae''. ''Proteromonas'' is notable by location of mastigoneme Mastigonemes are lateral "hairs" that attach to p ...

'') ****** Order Opalinida Poche, 1913 stat. n. Hall, 1953 em. Cavalier-Smith ******* Family Karotomorphidae Travis, 1934 (''

Karotomorpha ''Karotomorpha'' is a genus of parasites with a flagellum structure. This organism can infect a variety of higher life forms including a number of amphibians. For example, this genus is known to be a parasite of the rough-skinned newt, a widesp ...

'') ******* Family

Opalinidae 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 sunli ...

Claus, 1874 (e.g. ''

Cepedea ''Cepedea'' is a genus of heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular ...

'', '' Protoopalina'', ''

Opalina ''Opalina'' is a genus of parasitic heterokonts found in the intestines of frogs and toads. They lack mouths and contractile vacuoles, they are covered with nearly equal flagelliform cilia, and they have numerous nuclei, all similar. All the spe ...

'') ***** Class

Zierdt et al., 1967 ****** Order Blastocystida Zierdt, 1978 ******* Family Blastocystidae Jiang and He, 1988 (type genus '' Blastocystis'' Aléxéieff, 1911)

References

{{Taxonbar, from=Q2024928 Placidozoa