Heliozoa

Heliozoa, or sun animalcules, are roughly spherical amoeboids with many stiff, microtubule-supported projections called axopods radiating outward from the cell surface. These give them the characteristic sun-like appearance for which they are named, and are variously used for capturing food, sensation, movement, and attachment. They are similar to radiolaria, but they are distinguished from them by lacking central capsules and other complex skeletal elements, although some produce simple scales and spines. They may be found in both fresh water and marine environments.

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Originally the heliozoa were treated together as a formal class Heliozoa or Heliozoea, but the various orders show notable differences and are no longer believed to be related. Instead, heliozoa is regarded as a descriptive term applying to various lines of protists. These include the following:

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• Actinophryids and some other axodines
• Centrohelids
• Desmothoracids
• Dimorphids
• Sticholonche

Several nucleariids were once considered heliozoa, but they do not have microtubule-supported axopods and so are now considered filose amoeboids instead.

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Animalcule: Animalcule is an older term for a microscopic animal or protozoan. Some better-known animalcules include:...

Amoeboid: Amoeboids are cells that move or feed by means of temporary projections, called pseudopods (false feet). They have appeared in a number of different groups. Some cells in multicellular animals may be amoeboid, for instance our white blood cells, which consume pathogens. Many protists exist as ind...

Microtubule: Microtubules are protein structures found within cells. They have diameter of ~ 24 nm and varying length from several micrometers to possible millimeters in axons of nerve cells....