ASK THE AQUARIUM: Sea Cucumber Takes on Many Shapes
Q. We found something on the beach that someone said was a sea cucumber. Is there such a thing?
A. Sometimes truth is stranger than fiction. Yes, there is such a thing as a sea cucumber. Actually, it's a relative of sea stars, sand dollars and sea urchins, even though it looks nothing like them. All are echinoderms and have a five-spoke pattern, which isn't obvious to the casual observer.
The sea cucumber you found was most likely reddish-brown and looked like a prickly sausage or golf ball. That's because these animals can take on most any shape. This flexibility enables them to squeeze under rocks and ledges and into crevices to escape predators or avoid strong waves and currents. When you find a sea cucumber on the beach, it has usually been tossed ashore by rough seas.
It's hard to tell which end is which on these animals. When they're stressed they withdraw the tentacles that ordinarily protrude from the front. They live in a variety of environments -- sometimes submerged and attached to rocky surfaces by their tube feet, sometimes hanging onto rocks and ledges in crevices. Others live in shallow water or near low tide level, and still others inhabit deeper water and lie exposed on a rocky floor, sandy surface, or mud flat. Some burrow into sandy mud and are never seen.
These odd sea creatures are slow movers, getting around on rows of tiny tube feet, except for the sand-burrowing variety, which move by muscle contraction. All feed using sticky, slimy tentacles to snare microscopic plants and animals.
Sea cucumbers have a well-developed sense of touch, but are relatively insensitive to light. Their tough, leathery skin offers some protection against predators, such as fish and crabs, but some species have most unusual forms of self-defense.
Warty glands on the surface exude tough, sticky, repellent threads. In many cases, the animal contracts and forces out its internal organs! The attacker dines on the organs and leaves the cucumber's empty, leathery body casing to regenerate a new inside. Sand-burrowing cucumbers break into two or more pieces when roughly handled and regenerate the missing part -- a cool survival technique.
The state operates three public aquariums; one in Pine Knoll Shores, another at Fort Fisher and a third on Roanoke Island. The aquariums are administered by the North Carolina Department of Environment and Natural Resources, and are designed to inspire appreciation and conservation of North Carolina's aquatic environment. For more information about the Aquariums, visit www.ncaquariums.com, or call 800-832-FISH.
Sherry White works for the North Carolina Aquariums.
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