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Heliozoa
 
 
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Heliozoa, or sun animalcule
Animalcule

Animalcule is an older term for a microscopic animal or protozoa. Some better-known animalcules include:* Rotifers, called wheel animalcules...
s, are roughly spherical amoeboid
Amoeboid

Amoeboids are unicellular life-forms characterized by their similarity to amoebas....
s with many stiff, microtubule
Microtubule

Microtubules are one of the components of the cytoskeleton. They have a diameter of 25 Nanometre and length varying from 200 nanometers to 25 micrometers....
-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.






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Heliozoa, or sun animalcule
Animalcule

Animalcule is an older term for a microscopic animal or protozoa. Some better-known animalcules include:* Rotifers, called wheel animalcules...
s, are roughly spherical amoeboid
Amoeboid

Amoeboids are unicellular life-forms characterized by their similarity to amoebas....
s with many stiff, microtubule
Microtubule

Microtubules are one of the components of the cytoskeleton. They have a diameter of 25 Nanometre and length varying from 200 nanometers to 25 micrometers....
-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.

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:

  • Actinophryid
    Actinophryid

    The actinophryids are small,familiar group of heliozoan protists. They are the most common heliozoa in fresh water, and are especially frequent in lakes and rivers, but a few are found in marine and soil habitats as well....
    s and some other axodine
    Axodine

    The axodines are a group of unicellular heterokont algae. They characteristically have asingle emergent flagellum, which lacks the root structure found in related groups, and is extended into a wing-like form supported by an internal rod....
    s
  • Centrohelid
    Centrohelid

    The centrohelids or centroheliozoa are a large group of heliozoan protists. They include both mobile and sessile forms, found in freshwater and marine environments, especially at some depth....
    s
  • Desmothoracid
    Desmothoracid

    The desmothoracids are a group of heliozoan protists, usually sessile and found in freshwater environments. Each adult is a spherical cell around 10-20 ?m in diameter surrounded by a perforated organic lorica or shell, with many radial pseudopods projecting through the holes to capture food....
    s
  • Dimorphid
    Dimorphid

    The dimorphids or heliomonads are a small group of heliozoa that are unusual in possessing flagellum throughout their life-cycle. There are two genera: Dimorpha, a tiny organism found in freshwater, and the larger Tetradimorpha, which is distinguished by having four rather than two flagella....
    s
  • Gymnosphaerid
    Gymnosphaerid

    The gymnosphaerids are a small group of heliozoan protists found in marine environments. They tend to be roughly spherical with radially directed axopods, supported by microtubules in a triangular-hexagonal array arising from an amorphous central granule....
    s
  • Sticholonche
    Sticholonche

    Sticholonche is a peculiar genus of protozoan with a single species, S. zanclea, found in open oceans at depths of 99-510 metres. It is generally considered a heliozoan, placed in its own order, called the Taxopodida....


Several nucleariid
Nucleariid

The nucleariids are a small group of amoeboide with filose pseudopods, known mostly from soils and freshwater. They are distinguished from the similar vampyrellids mainly by having mitochondrion with discoid cristae....
s were once considered heliozoa, but they do not have microtubule-supported axopods and so are now considered filose amoeboids instead.