But, colonies may live for many years and can grow to immense sizes. Individual coral organisms, called polyps, are simple vase- shaped creatures. Each has a central mouth, surrounded by a ring of tentacles.
Lobe colonies consist of thousands of polyps, all descendants of one original founding individual.
Many corals can function as carnivores, using their tentacles to capture small planktonic animals drifting over the reef. Special stinging cells that line the surfaces of the polyps' tentacles entangle and paralyze their prey. Other corals are suspension feeders, using hair-like structures called cilia to collect particles of organic matter that drift down from above. The polyps of lobe coral are so small that researchers question if they are actually capable of capturing prey. But, corals also act as primary producers.