| Commation | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Clade: | incertae sedis |
| Order: | Commatiida Cavalier-Smith, 1997[3] |
| Family: | Commatiidae Cavalier-Smith & Scoble, 2013[2] |
| Genus: | Commation Thomsen & Larsen, 1993[1] |
| Type species | |
| Commation eposianum Thomsen & Larsen, 1993[1] | |
| Species[1] | |
Commation is agenus ofmarineheterotrophicprotists closely related to theactinophryids. It contains twospecies,Commation cryoporinum andCommation eposianum, discovered inantarctic waters and described in 1993.[1] Currently, the genus is classified within amonotypicfamilyCommatiidae andorderCommatiida.[2] Along with thephotosyntheticraphidophytes, these organisms compose theclass ofstramenopiles known asRaphidomonadea.[4]
The name of the genus,Commation, derives from Latin comma, referring to the overallcomma shape of the biconvex cells.[1][2]
Commation is a genus ofunicellulareukaryotes. They are solitaryplanktonic organisms that live as circular or oval, sometimes flattened, cells with aproboscis. Occasionally, a singleflagellum with tripartite hairs (ormastigonemes) emerges from the proximity of the proboscis. They predominantly move bygliding, a motion facilitated by excretion of mucus. Thecell nucleus appears at the base of the proboscis. The presence of two flagellarbasal bodies hints at theirstramenopile origin, since twoheterokont flagella (one smooth, one with mastigonemes) are the main distinguishing trait of the Stramenopiles. They also present microtubular roots and a striated root orrhizoplast, a fiber connecting the nucleus to the basal bodies.[1]
Themitochondria ofCommation species have tubularcristae. One or more types of extrusomes occur scattered throughout thecytoplasm. One species,C. cryoporinum, presents two types of extrusomes, some of them visible underlight microscopy when large enough. The other species,C. eposianum, only contains one type of extrusome that is not visible.[1] The complexcytoskeleton ofCommation contains structures consisting ofmicrotubular arrays and electron-dense structures, present in both the cell bodies and proboscis.[1]
Commation cells arephagotrophic and non-photosynthetic,[1] unlike theirraphidophyte relatives.[2] They live asplankton on theAntarctic Ocean, and were obtained at a depth of 10–20 meters. A single cell similar toC.eposianum was found in acover slip preparation belonging to a 1989 sample obtained from aPacific Ocean cruise offCalifornia, indicating that the genusCommation may not beendemic to the Antarctic region.[1] Despite being heterotrophic, they are classified as part of thephytoplankton in ecological surveys.[5]
Commation was described as agenus by twobiologists of theUniversity of Copenhagen,Helge Abildhauge Thomsen andJacob Larsen. The description was published in 1993 on theEuropean Journal of Protistology.[1] Subsequenttaxonomic research papers assignedCommation to amonotypicfamilyCommatiidae[2] and orderCommatiida. The order Commatiida was initially assigned to the classKinetomonadea on the basis of branched tubularmitochondrial cristae.[3]Phylogenetic analyses in 2013 demonstrated that bothCommation and a group ofheliozoa known asActinophryida were related to theraphidophytealgae. The first two groups, whileheterotrophic, were united in the subclassRaphopoda, while the raphidophyte algae were given their own subclassRaphidophycidae. Together, these two subclasses currently compose the classRaphidomonadea.[4]
Twospecies have been described:[1]