Hall, Richard P. Formerly, University of California, Los Angeles, California.
A subclass of the Actinopodea. Unlike Radiolaria, these protozoans have no central capsule. Most species live in fresh water. Pseudopodia may be either slender with an axial filament surrounded by cytoplasm (axopodia) or filamentous (filopodia). Axopodial filaments can be extended or retracted rapidly by mechanisms not yet explained. Certain floating species can roll along on the tips of their axopodia and also swim by moving their axopodia. Some species are naked; others have skeletal elements ranging from siliceous scales or spicules embedded in a gelatinous capsule to a reticulate chitinous skeleton often impregnated with silica. A centroplast may or may not be present. The subclass has three orders. Actinophryida lack skeletons and centroplasts and include both uninucleate and multinucleate genera (illus. a). In the Centrohelida, a centroplast is present or else is assumed to be because the nucleus is eccentric (illus.b). The organisms may be covered with a gelatinous sheath or with a skeleton composed of discrete siliceous elements embedded in such a layer. The Desmothoracida have a perforate continuous skeleton which is composed of chitin, and sometimes impregnated with minerals (illus.c). See also: Actinophryida; Actinopodea; Centrohelida; Desmothoracida; Protozoa; Sarcodina; Sarcomastigophora
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Its dedicated editorial team is led by Sagan Award winner John Rennie. Contributors include more than 9000 highly qualified scientists and 39 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 17,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information