Anemones and Corals: Anthozoa

Anemones (uh-NEH-muh-nees) and corals are polyps (PAH-luhps), which are tubular sacs with a mouth and tentacles on a flattened upper surface called the oral disk. Most of these animals have stingers in their tentacles. The mouth and tentacles face up, and the base of the polyp is attached to the material on which the animal lives. The mouth opening leads into a digestive cavity. Hairlike fibers lining the digestive tract funnel water into the body. Anemones and corals live alone or in colonies. Solitary animals are commonly 0.5 to 2 inches (1.3 to 5 centimeters) in diameter at the oral disk, but the largest species grows to 3 feet (1 meter) across. The polyps of colonial species are typically smaller than those of anemones and corals that live alone, but the colonies themselves can be quite large. Anemones and corals look like flowers, bushes, feathers, fans, and even a brain.

Many species of anemones and corals make skeletons. In some of these species the living tissue lies above an outer skeleton made of calcium carbonate secreted by the outer layer of tissue. It is these skeletons that form the framework of tropical coral reefs. Other species secrete a flexible black inner skeleton that has thorns on its surface. Still other species secrete an inner skeleton made of calcium carbonate, a protein called gorgonin, or a combination of the two. Soft corals lack a supporting inner skeleton and can inflate or deflate by funneling water into or out of themselves.