Patterson, David J. Department of Zoology, University of Bristol, Bristol, United Kingdom.
Last reviewed:August 2019
- Additional Reading
An order of Heliozoia. These protozoans are characterized by stiff arms radiating from the central cell mass. Each arm is supported internally by an array of microtubules which terminate on the surface of nuclei. The organisms are found in freshwater, marine, and soil habitats. They feed on other protozoans which collide with and stick to the arms. Well-studied genera are Actinophrys (illus.a), with a single central nucleus, Actinosphaerium, and Echinosphaerium (illus.b); the latter two have many nuclei lying just internal to a peripheral layer of vacuoles. The body size ranges from 50 to several hundred micrometers. Actinophryids form cysts within which a type of uniparental sexual reproduction occurs. See also: Actinopodea; Heliozoia; Protozoa; Sarcodina
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