Jackie Shopf, age 13, of Conestoga, Pennsylvania, for her question:
Is coral a plant or animal?
In the Caribbean Sea around the West Indies, skin divers get a chance to behold living corals in all their glory. They grow like gaudy gardens on rocky reefs below the surface, where the shadowy blue green water is speckled with rippling sunbeams. They look like multi colored flower gardens, where plumy and fan shaped coral blossoms crowd cheek to cheek with whopping coral mushrooms and heads of lettuce. Here and there, a pronged coral staghorn suggests that a miniature deer is hiding among the colorful bushes.
The chunk of coral you buy in a novelty store looks for all the world like a petrified white bush of delicate twiggery. Actually it is a vacant apartment house, once occupied by a colorful colony of living coral creatures. Please do not feel embarrassed when you mistake them or their residence for members of the plant world. They certainly look like plants but they are not.
Many years ago, experts sorted the various corals, the daisy faced sea anemones and a number of ocean going polyps into a class of their own. They name they chose for this class was Anthrozoa, which means plant animals but they are really animals.
Most of the world's 2,500 coral species dwell in warm, fairly shallow sea water. Their bodies are polyps shaped somewhat like mini trees. The gristly trunk is a hollow stomach and the branches form a ring around the open mouth. Actually, those flower tinted branches are tiny tentacles, waving to and fro to catch a tiny swimmer for dinner. In some species, a juice is secreted to stun the struggling victim before the tentacles poke him down through the mouth.
The life story of the corals is quite remarkable and it may vary from species to species. Sperm and ova cells may be strewn into the water, where the pairs meet and fertilize. The next stage is a swimming larva called a planula. Soon it fixes itself to a firm foundation and builds the stony room, where it will spend the rest of its life.
Many corals multiply by sprouting buds on their trunks. When ready, the buds break loose and because mature polyps. Usually they attach their private rooms to the family apartment house. Given time, a single coral can produce a colony of 20 million polyps. Among the separate rooms there are corridors so that the sea water can deliver oxygen and fragments of food to all the tenants.
A chunk of dry coral is whitish limy material. When it was under water, it was pink or purple, orange or blue or some other pastel color. This flowery touch was added by the bodies of living coral animals. Each tiny room has a window and the polyp inside pokes his petal tinted tentacles outside, hoping to catch a passing morsel of meat.