heliozoan

Heliozoa are phagotrophs.^[1] They 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.

Groups

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.

The primary groups include:^[2]

• Actinophryida
• Centrohelida
• Desmothoracida

Other groups include:

• Dimorphids
• Gymnosphaerids
• Sticholonche

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

References

External links

Actinosphaerium (single-celled) is an example of a heliozoa. For an image see

• http://www.microscopy-uk.org.uk/index.html?http://www.microscopy-uk.org.uk/ponddip/