14 Most are planktonic.
Heliozoans live primarily in fresh water.
Radiozoans are primarily marine and have delicate shells, usually made of silica. Cytoplasmic strands extend through the shell's pores and function in swimming, feeding and shell formation. Many have symbiotic algae living beneath the shell which provide nourishment through photosynthesis. Foram shells are an important component of sediments and sedimentary rocks. All species of the phylum Apicomplexa are parasites of animals.