What are fire corals? Well, they’re not true corals, although their talent for stinging certainly lives up to the fire part of its name. The tiny animals behind them are hydrocorals, hydroids that build calcium carbonate dwellings. They’re closer to jellyfishes than to the stony corals they sort of resemble. THE FIRST THING TO SAY ABOUT FIRE CORALS IS A WARNING: THEY LOOK TOTALLY INNOCENT. But touching them, presumably accidently, has caused many a diver
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WHEN PEOPLE SEE THE WORD “CORAL,” it very likely brings to mind the great mounds of star and brain corals that stand out on the reefs. In fact, “corals” include many organisms beyond the familiar stony formations, all built on similar, tiny, coral polyps. “Coral” itself is a flexible word. It applies to the coral exoskeletons that we see as the visible shells of hard corals, to the polyp animals that live within those exoskeletons
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Corallite (kawr’–uh-lahyt) The calcium carbonate exo-skeleton of a coral polyp. Polyp (pol’-ip) With regard to coral reefs, a tiny, colonial, sac-like animal fixed to a substrate and protected by a calcium carbonate external skeleton. Zooxanthellae (zoh-uh-zan-thel’-ee) Symbiotic dinoflagellate algae embedded in the tissues of coral polyps that perform photosynthesis to produce nutrients shared with the host polyps. A major factor in the growth of reef-building corals.
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ONE OF THE WONDERS OF TROPICAL REEFS IS THE DAZZLING ARRAY OF COLORS EXHIBITED BY THE CORALS that constitute the foundation of reefs. Coralheads sitting side by side on a reef can display different colors and different shades and intensities of the same colors. New research has indicated that, rather than random phenomena for dramatic effect, corals’ variations in color involve genetic factors that help protect the symbiotic algae – zooxanthellae – embedded in coral
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WE’VE ALL HAD IT INSTILLED FIRMLY IN OUR CONSCIOUSNESS that coral reefs are living organisms. But, faced with the colorful, solid structures that we see when we go underwater, what does that actually mean? Those rock-like surfaces aren’t living substances themselves, but hard facades of calcium carbonate – essentially, limestone. The living animals – tiny soft coral polyps with slender tentacles – are ensconced underneath, protected by the cup-shaped calcium-based corallites they’ve manufactured. TINY, THIN
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