Even the most seasoned beachcomber is excited and pleased to find a whole, intact sand dollar on the beach. A common sand dollar is another name for a particular type of “flattened” sea urchin. The common sand dollar is found in the Northern Hemisphere in temperate and tropical waters. On a good day at Ocean Isle, Sunset or Holden Beach, you might find many sand dollars ranging in size from one to approximately four inches in diameter.
Sand dollars live on sandy or muddy flat areas of the ocean floor in shallow water near land. They often live in colonies. Female sand dollars release eggs that are fertilized externally. Interestingly, the newly hatched larvae can clone themselves as a means of self-defense. If threatened, they can double their numbers by halving their size, thereby lessening the chance of being detected. The larvae go through a few stages of development before forming an external skeleton that houses the animal’s internal organs. The skeleton is called a “test” and it is this sun-bleached skeleton that beachcombers find. If you find a sand dollar that is brownish and covered with short, dark, fur-like spines, the animal is alive and should not be removed from the beach.
A live sand dollar’s spines are covered with small hairs called “cilla.” By moving the cilla and spines, sand dollars are able to move across the sea beds in which they live. Mature sand dollars have few predators and can live up to ten years.
Beachcombers are most likely to find sand dollars at low tide, especially after a storm. The sun-bleached shells will be extremely fragile and will crumble or break easily. To preserve the sand dollars that you bring home, rinse them several times in fresh water, then soak them for 15 minutes in a water/bleach solution. When the sand dollars are dry, carefully paint them with a mixture that is half water and half white glue. The glue solution will make them less likely to break. Your beautiful sand dollars will last a long time if treated with care.
The Museum of Coastal Carolina has several sand dollars in its extensive shell collection. You can also see and handle live sea urchins in the museum’s touch tank. For more information, call 910-579-1016 or visit www.MuseumPlanetarium.org.