Haddon's carpet anemone can spread out over a meter wide and often hosts several species of clownfish at once. Its tentacles remain stinging to most fish, yet have no effect on its symbiotic tenants.
What defines this group — Cnidarians (corals, anemones, jellyfish)
Corals, anemones and jellyfish: the same simple animal, anchored to the bottom or drifting in open water.
All armed with cnidocytes, harpoon cells that fire on contact.
A body arranged in rays around a single opening, serving as both mouth and exit.
Hard corals host algae in their tissue: it is their departure that causes bleaching.