Coral is made up of many individual polyps, which are connected by living tissue. Each polyp is a cuplike shape, which has a ring of stinging tentacles around a central opening. These stinging cells are used for protection and to capture zooxanthellae -- small animal life -- for food. Coral secretes limestone -- calcium carbonate -- which forms an exoskeleton that join together to form the makeup of the reef.
With a misleading name -- the starfish is an echinoderm not a fish -- there are over 2,000 species of starfish worldwide. The species of starfish range from the more common five-arm versions to versions with over 40 arms. They have a hard calcified skin to protect them from predators and some have striking colors to intimidate potential attackers or for camouflage. Starfish can regenerate limbs and have the amazing ability to consume prey outside of their body.
Sea anemones are stinging polyps that are often attached to coral reefs or the sea bottom. They are related to coral and jellyfish and kill their prey by letting it swim into their tentacles. The body consists of a foot, a cylindrical body and the tentacles. There are more than 1,000 species of anemone around the world and they have become symbolized by their relationship with clown and anemone fish, which are protected by a mucus layer on their skin and make their home amongst the anemone tentacles.
Jellyfish drift along the coral reefs in ocean currents. The beautiful creatures have bell-shaped, tiny, stinging cells in their tentacles to stun or paralyze their prey before they eat them. Jellyfish propel themselves by shooting water from their mouths. Their tentacles can give a nasty sting; most jellyfish stinging is from humans accidentally touching them. Jellyfish digest their food very quickly and eat fish, plants, other invertebrates and even other jellyfish.
