Corals belong to a group of animals called Cnidarians. This includes hard and soft corals, sea fans, gorgonians, jelly fish and sea anemones. Amongst other common characteristics is the presence of stinging cells (nematocysts) which are used to catch prey.
A single coral animal is a polyp - the attractive "flowery" item looking like an anemone. The soft coral shown above is actually a colony of animals, each connected to its neighbour by living tissues. Soft corals are not reef-building, although they do secrete limestone. In their case this is as internal crystals called sclerites or spicules. Because soft corals do not have large skeletons, they grow faster than hard corals
Eight feathery tentacles surround the coral's mouth and whip food into it. They filter-feed: removing plankton from water flowing around the colony. Relatively recent data on soft corals indicates that they feed on very small planktonic particles, such as single-celled algae, rather than larger larvae as had previously been thought.
The photos above were taken in the egyptian Red Sea.
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