Cryomonadida is a group of

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

Rhizaria The Rhizaria are a diverse and species-rich clade of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus '' Paulinella'' in the phylum Cercozoa, they are all non-photosynthetic, but many Foraminifera ...

, that belong to the

Cercozoa Cercozoa (now synonymised with Filosa) is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by phylogeny, molecular phylogenies of rRNA and actin or Ubiqu ...

Characteristics

Members of the Cryomonadida are single-celled organisms that are surrounded by a shell comprising layers of organic material. They possess two unequally long

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

, and a single

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

with a distinct

nucleolus The nucleolus (; : nucleoli ) is the largest structure in the cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signa ...

. They have a laterally located

cytostome A cytostome (from ''cyto-'', cell and ''stome-'', mouth) or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacu ...

, from which

pseudopodia A pseudopod or pseudopodium (: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and ...

arise.

Systematics

The

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Cryomonadida was erected in 1993 for the genus ''Cryothecomonas''. In 2005, Sina Adl ''et al.'' did not include the order in their classification, but placed the genus ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' among the

. It became clear, however, that other genera, and taxa known only from

environmental DNA Environmental DNA or eDNA is DNA that is collected from a variety of environmental samples such as soil, seawater, snow or air, rather than directly sampled from an individual organism. As various organisms interact with the environment, DNA ...

, belonged in this group, and so in 2008 Jan Pawlowski placed the Cryomonadida as part of the core Cercozoa. Within the Cercozoa, the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to Cryomonadida is Ebriacea; ''

Pseudodifflugia ''Pseudodifflugia'' is a genus of Endomyxa. It was described in 1845. References Rhizaria genera {{Cercozoa-stub ...

'' is also closely related. The following genera are included: * Family Rhogostomidae Dumack et al. 2017 ** '' Sacciforma'' Dumack et al. 2017 ** '' Capsellina'' Penard 1909 ** '' Rhogostoma'' Belar 1921 (previously misidentified as '' Lecythium'')Adl, S.M. ''et al.'' (2012). The revised classification of eukaryotes. ''Journal of Eukaryotic Microbiology'' 59 (5): 429–514

* Family Protaspidae Cavalier-Smith 1993 ryothecomonadidae Cavalier-Smith 1993** '' Cryothecomonas'' Thomsen et al. 1991 ** '' Protaspa'' Cavalier-Smith 2011 'Protaspis'' Skuja 1939 non Bryant 1933">Protaspis.html" ;"title="'Protaspis">'Protaspis'' Skuja 1939 non Bryant 1933ref name="Hoppenrath"/> ** ''Sinistermonas'' Lee 2015

References

{{Taxonbar, from=Q1142230 Rhizaria orders