Vorticella protozoa on duckweed, light microscopy footage. These ciliate protozoa have bell-shaped heads with tiny, hair-like structures (cilia) which are moved in a waving motion to waft food towards them from the surrounding fluid. The cilia can also be used for movement. Each head is attached to a stalk which the vorticella uses to secure itself to an anchor-point. The vorticellae feed in an extended position, and when disturbed they contract their stalk for protection.