Coral Polyps

f22 @ 1/60s, Kodachrome 25 slide film, ASA:25, Nikonos II w 35mm, 1:2 extension tube, Oceanic flash and aluminum flash reflector

"Coral Polyps," Coral Reef Alliance. Coral reefs are built by and made up of thousands of tiny animals—coral “polyps”—that are related to anemones and jellyfish. Polyps can live individually (like many mushroom corals do) or in large colonies that comprise an entire reef structure. A polyp has a sac-like body and an opening, or mouth, encircled by stinging tentacles called nematocysts or cnidae. The polyp uses calcium and carbonate ions from seawater to build itself a hard, cup-shaped skeleton made of calcium carbonate (limestone). This limestone skeleton protects the soft, delicate body of the polyp. Coral polyps are usually nocturnal, meaning that they stay inside their skeletons during the day. At night, polyps extend their tentacles to feed.

Salt River Canyon, St. Croix, U.S. Virgin Islands

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