Sand dollars are marine invertebrates belonging to the class Echinoidea, making them close relatives of sea urchins and sea stars. They live in sandy or muddy substrates in shallow coastal waters across the globe. As detritivores, they filter microscopic algae and organic debris from the water, helping maintain the ocean floor’s nutrient balance. Since sand dollars are highly sought-after souvenirs, recognizing the distinction between a live specimen and a naturally discarded skeleton is important for ethical beachcombing.
Identifying a Living Sand Dollar
The difference between a live and dead sand dollar is immediately apparent in its appearance and texture. A living sand dollar is not the bleached white color seen in gift shops, but rather a dark shade of brown, reddish-purple, or gray. This coloration is hidden beneath a dense layer of tiny, hair-like spines called cilia, which give the surface a soft, velvety appearance.
These flexible spines are constantly in motion, helping the animal move across the seabed and directing food toward its central mouth opening. If gently touched, you may feel this velvety layer subtly shifting or see the spines wiggling, which is a sign of life. A live specimen may also release echinochrome, a harmless, yellowish-orange substance that acts as a mild dye. If there is any doubt about its status, return it to shallow, calm water and observe it. A live sand dollar will attempt to burrow into the sand within a few minutes, using its spines and tube feet to disappear beneath the surface. Taking a live sand dollar from the beach is prohibited in many coastal areas and harms the local marine ecosystem.
Characteristics of a Dead Shell
A sand dollar safe to collect is one that has died naturally, allowing its soft tissues to decay and wash away. What remains is the animal’s hard, internal skeleton, called the test, which is composed primarily of calcium carbonate. The test will be completely smooth and bald, having lost all the minute, dark-colored spines that covered its surface when the animal was alive.
Exposure to the sun and air naturally bleaches the test, turning it a uniform, dry white or pale gray color. The familiar five-pointed, flower-like pattern, which marks the ambulacral areas, becomes prominently visible. Many species also feature distinct, elongated openings called lunules, which are defined holes penetrating the test. A dead sand dollar is brittle and fragile, lacks movement or discernible odor, and is the only type appropriate for collection.
Cleaning and Preserving Beach Finds
Once a naturally deceased sand dollar test is confirmed, it requires simple cleaning for preservation and display. First, soak the test in clean freshwater for several hours to remove residual salt or sand particles. After this initial rinse, a brief soak in a diluted solution of water and hydrogen peroxide or bleach can further whiten and sanitize the test.
The sand dollar should then be removed from the solution and allowed to air dry completely, preferably in a spot with good ventilation. Because the test is fragile and susceptible to crumbling, a simple hardening treatment is applied to increase durability. This involves gently brushing a 50/50 mixture of white craft glue and water onto both sides of the dried test. Applying two or three thin coats, allowing each to dry fully, will strengthen the delicate structure without obscuring its natural beauty.