Nucleariida is a group of

amoeba An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudop ...

e with filose

pseudopods A pseudopod or pseudopodium (plural: 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 filamen ...

, known mostly from soils and freshwater. They are distinguished from the superficially similar vampyrellids mainly by having mitochondria with

discoid Discoid may refer to: * Disk (mathematics), the region in a plane enclosed by a circle Medicine * Furosemide, a medication sold under the trade name Discoid * Discoid meniscus, a human anatomical variant * Discoid lupus erythematosus, a chroni ...

cristae, in the absence of superficial granules, and in the way they consume food.

Classification

Molecular studies indicate that nucleariids are closely related to fungi. and more distantly to the lineage that gave rise to choanoflagellates and metazoa

opisthokont The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and ...

s, the group which includes

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

. Some use a broad definition of

Opisthokont The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and ...

a to include all of these organisms with flattened mitochondrial cristae. The genera '' Rabdiophrys'', '' Pinaciophora'', and '' Pompholyxophrys'', freshwater forms with hollow siliceous scales or spines, were included in Nucleariida by some. This was disputed by Smith and Chao who placed them in the

Rhizaria The Rhizaria are an ill-defined but species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many forami ...

. Their affinity with the nucleariids has been confirmed. Historically, nucleariids were included among the

heliozoa Heliozoa, commonly known as sun-animalcules, are microbial eukaryotes ( protists) with stiff arms ( axopodia) radiating from their spherical bodies, which are responsible for their common name. The axopodia are microtubule-supported projections f ...

as the Rotosphaerida because both they and heliozoa had ropunded bodies and radiating pseudopodia. According to a 2009 paper, '' Fonticula'', a cellular

slime mold Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mul ...

, is an opisthokont and more closely related to ''Nuclearia'' than to fungi.

Characteristics

Nucleariids ('' Nuclearia'' and '' Micronuclearia'') are usually small, up to about 50 μm in size.

References

{{Taxonbar, from1=Q1048747, from2=Q13403500 * Opisthokont orders