Radiolaria

The radiolaria comprise three groups of amoeboids protists which form intricate mineral skeletons. They feed and move by means of axopods, and have a frothy ectoplasm often including symbiotic zooxanthellae, which is separated by a central capsule. Among the Polycystinea[?] and Phaeodarea[?], the skeleton is made of silica and sometimes organic materials, but among the less common Acantharea it is made of strontium sulfate.