How many body openings do cnidarians have?

Cnidarians have one body opening. There is no mouth or anus. Instead, food particles are drawn into the body by movement of water. Inside the body cavity are specialized cells called amoebocytes and collar cells that help digestand remove wastes. Cnidarians with the opening at the top have body plans called polyps, such as corals. Those with the opening underneath have a medusa body form, such as jellyfish.