Suctorians are ciliates that become sessile – attaching to material with a stalk – and feed by extracellular digestion. Suctorians are covered by tentacles that emanate from the organism’s central cell body. The tentacles quickly immobilize and capture small organisms that come into contact with them before sucking nutrients out of their prey.

This video shows a Suctorian’s tentacle movement mechanism. The central tentacle is wrapped with a spring-shaped sheath which can contract and expand to move the tentacle.