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Science

A Lesson from under the Sea

by Sharene Martin

Creatures of the sea have fascinated land-dwellers for thousands of years. Always mysterious, marine life provides some of the best examples of how deceptive outer appearances can be. Many creatures look and behave as expected. Others, such starfish and sea horses, are living proof that things are not always as they seem.

Starfish, or sea stars, are the most visible examples of how looks can be deceiving. Starfish are nothing like stars in the sky. Of the sixteen hundred species living at the bottoms of oceans around the world, most are brightly colored. They are shaped like a five-sided pentagon or a many-rayed sun, rather than a five-pointed star.

While starfish may look harmless lying among seaweed and corals, they can be dangerous predators when they are hungry. But, starfish have no taste for humans. They prefer eating oysters, scallops, and other mussels. Once a starfish attaches itself to an oyster's shell, it uses suckers located on the underside of its arms to open the shell. It then squeezes part of its stomach out onto the oyster and digests the mussel with a special fluid.

Occasionally a larger sea creature will try to make a meal out of a starfish, and in the struggle to survive, the starfish may lose a ray. Luckily, starfish can regenerate their rays. Sometimes the lost ray may become a whole new starfish!

Another sea dweller unique in appearance and able to regenerate lost parts is the sea horse, or sea dragon. This strange-looking, bony-plated creature has a horse's head and a monkey's tail. It moves by being carried by ocean currents or by using its dorsal fin, which can be regenerated when lost.

Sea horses reproduce in a most unusual way. The female lays her eggs in the male’s pouch, which is similar to a kangaroo's pouch. The male sea horse carries the eggs for ten to forty-five days. After the eggs hatch, he expels more than one hundred babies into the water. These newborns quickly swim away and begin their hunt for food.

Using its monkey-like tail, the hungry sea horse anchors itself to a branch of coral and floats on the bottom of the ocean. It scours the water with eyes that can see in two directions at once. When the sea horse spots fish larvae, plankton, or a baby shrimp floating on by, the sea horse will try to suck it up through its straw-like snout.

Studying these marine creatures can help humans learn more about the strange and wonderful world at the bottom of the ocean, where a creature’s outer appearance might be deceptive. While many other land and sea dwellers may behave exactly as it appears they should, the existence of the extraordinary starfish and remarkable sea horse reminds us that what we see is not always how things really are.

The End

Bibliography

Animal Bytes—Sea Horse. http://www.seaworld.org. September 24, 2001.

Ask Shamu: Seastars. http://www.seaworld.org. September 24, 2001.

Charton, Barbara. The Facts on File Dictionary of Marine Science. New York: Facts on File, 1988.

Fichter, George S. Starfish, Seashells, and Crabs. Racine, Wisconsin: Western Publishing Company, 1993.

Morris, Rick. Mysteries and Marvels of Ocean Life. London: Usborne Publishing, 1983.

Parramon, J. M., and G. Sales. My First Visit to the Aquarium. New York: Children's Press Choice, 1990.

Perry, Phyllis J. Sea Stars and Dragons. New York: Franklin Watts, 1996.

Schlein, Miriam. The Dangerous Life of the Sea Horse. New York: Antheneum, 1986.

Photos courtesy of N.O.A.A.

A language and science teacher for many years, Sharene Martin has been writing educational materials for children since 1989. Her first trade picture book, THIS MOMMA, THAT MOMMA will be available in 2005.

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