It is divided by walls or septa, which arise as folds from the body wall. These folds, along with the mouth and pharynx, are usually arranged in a biradially symmetric pattern. Anthozoans include sea anemones, a variety of corals, sea fans, and sea pens. Sea anemones are carnivorous polyps that are quite large, ranging up to 200mm in length. They tend to be brightly colored.
Most species live in warm water.
They feed on fishes, which are caught by means of the numerous nematocysts in their tentacles. These animals are known for their symbionts. These include species of fish that actually live among the tentacles of large anemones, somehow avoiding lethal contact with the nematocysts. Other anemones have unicellular algae living within their tissues, from which they probably derive some nutrition. Yet others have a symbiotic relationship with hermit crabs, which gather up the anemones and place them on the snail shells that the crabs occupy.