Order Desmothoracida, the desmothoracids, are a group of

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 fro ...

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

s, usually sessile and found in freshwater environments. The adult is a spherical cell around 10-20 μm in diameter surrounded by a perforated organic lorica, or shell, with many radial

pseudopod 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 ...

s projecting through the holes to capture food. These are supported by small bundles of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

s that arise near a point on the

nuclear membrane The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membrane ...

. Unlike other heliozoans, the microtubules are not in any regular geometric array, there does not appear to be a microtubule organizing center, and there is no distinction between the outer and inner

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

. Reproduction takes place by the budding-off of small motile cells, usually with two

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

. Later these are lost, and the pseudopods and lorica are formed. Typically, a single lengthened pseudopod will secrete a hollow stalk that attaches the cell to the substrate. The form of the flagella, the tubular cristae within the

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

, and other characters have led to the suggestion that the desmothoracids belong among what is now the

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

. This was later confirmed by genetic studies. As of the year 2000, the order Desmothoracida contained five

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

with a total of 10 species.Mikrjukov, K. A. (2000)
Taxonomy and phylogeny of Heliozoa. 1. The order Desmothoracida Hertwig et Lesser, 1874.
''Acta Protozoologica'' 39(2) 81-97. * Order Desmothoracida Hartwig & Lesser 1874 emend. Honigberg et al. 1964 ** Family Clathrulinidae Claus 1874 *** Genus ''

Clathrulina Order Desmothoracida, the desmothoracids, are a group of heliozoan protists, usually sessile and found in freshwater environments. The adult is a spherical cell around 10-20 μm in diameter surrounded by a perforated organic lorica, or shell, wi ...

'' Cienkowski 1867 'Podosphaera'' Archer 1868 non Kunze 1823; ''Elaster">Podosphaera.html" ;"title="'Podosphaera">'Podosphaera'' Archer 1868 non Kunze 1823; ''Elaster'' Grimm 1872; ''Eleaster'' (sic) Schmidt 1913; ''Orbulinella'' Entz 1877] **** Species ''Clathrulina elegans'' Cienkowski 1867 [''Clathrulina ovalis'' (von Daday 1885) Deflandre, 1926; ''Clathrulina cienkowskii ovalis'' von Daday 1885; ''Clathrulina cienkowskii'' Mereschkowsky 1879; ''Clathrulina stuhlmanni'' Schaudinn 1897; ''Podosphaera haeckeliana'' Archer 1868; ''Elaster greeffi'' Grimm 1872] **** Species '' Clathrulina smaragdea'' (Entz 1877) Mikrjukov 2000 'Orbulinella smaragdea'' Entz 1877; ''Orbulinella salina'' Labbe 1924*** Genus ''

Hedriocystis Order Desmothoracida, the desmothoracids, are a group of heliozoan protists, usually sessile and found in freshwater environments. The adult is a spherical cell around 10-20 μm in diameter surrounded by a perforated organic lorica, or shell, wi ...

'' Hertwig & Lesser 1874 **** Species '' Hedriocystis pellucida'' Hertwig & Lesser 1874 **** Species '' Hedriocystis minor'' Siemensma 1991 **** Species '' Hedriocystis zhadani'' Mikrjukov 2000 *** Genus '' Penardiophrys'' Mikrjukov 2000 **** Species '' Penardiophrys reticulata'' (Penard 1904) Mikrjukov 2000 'Hedriocystis reticulata'' Penard 1904**** Species '' Penardiophrys spinifera'' (Brown 1918) Mikrjukov 2000 'Hedriocystis spinifera'' Brown 1918*** Genus '' Cienkowskya'' Schaudinn 1896 non Regel & Rach 1859 non Solms 1867 'Cienkowskia'' Weldon & Hickson 1909 non Rostafinski 1873 non Schweinfurth 1867 non Solms 1867; ''Wagneria">Cienkowskia.html" ;"title="'Cienkowskia">'Cienkowskia'' Weldon & Hickson 1909 non Rostafinski 1873 non Schweinfurth 1867 non Solms 1867; ''Wagneria'' Cienkowsky 1881 non Robineau-Desvoidy 1830 non Gistl 1848 non Alenitzin 1873 non Lemaire 1857 non Hesse 1912 non Heilprin 1887 non McCook 1895 non Jedlicka 1935 non Denier 1933 non Meladze 1967; ''Monomastigocystis'' de Saedeleer 1930] **** Species ''Cienkowskya mereschkovckii'' (Cienkowsky 1881) Schaudinn 1896 [''Wagneria mereschkowskyi'' Cienkowsky 1881] **** Species ''Cienkowskya brachypous'' (De Saedeleer 1930) Mikrjukov 2000 'Monomastigocystis brachypous'' de Saedeleer 1930; ''Hedriocystis brachypous'' (De Saedeleer 1930) Siemensma 1991*** Genus '' Actinosphaeridium'' Zacharias 1893 'Actinopshaeridium'' (sic)**** Species '' Actinosphaeridium pedatus'' Zacharias 1893 'Nuclearia caulescens'' Penard 1903

Notes

References

* {{Taxonbar, from1=Q151237, from2=Q33181010 Filosa Amoeboids