What is a Sand Dollar?

A sand dollar is a marine animal named after its flattish, round shape that resembles a large coin. This type of animal belongs to a class of animals known as Echinoids and are close relatives of the sea urchin and starfish. Many people are familiar with sand dollars that have washed up on the beach, becoming bleached by the sun to a light sandy color. When this animal is alive however, it is darker in color and covered by tiny, mobile spines.

A sand dollar has a characteristic 5-petal design on its back produced by sets of large pores. When it is alive, rows of tiny tubular feet extend up through the pores. These respiratory stalks or podia act as gills by flushing water through the sand dollar to keep it oxygenated.

Most species of sand dollars live on or just under the seabed in muddy or sandy areas at depths of about 30–40 feet (9-12 meters). The tiny spines covering their exoskeletons are covered with minute hairs, or cilia. On the underside of the animal, these spines and hairs relay food particles along grooved lines in the hardened skin that lead to a central hole where the mouth is located. The spines and hairs also aid in movement along the sea floor.

The small, circular opening in the underside of the sand dollar hardly seems sufficient for a mouth, but this animal does have teeth. If you shake the bleached skeleton of a sand dollar (called a test) you’ll likely hear something rattling inside. Break open the test and you’ll find several small white pieces that served as teeth.

Sand dollars are usually found in large groups and have limited enemies due to the tough outer shell along with negligible inner meat. Some predators of these animals include starfish, snails and certain fish. The animal gives birth by releasing larvae through the top pores of the exoskeleton. The young are carried along ocean currents for miles, and those that survive go through many stages before developing the outer calcium-hardened shell of the adult sand dollar.

Sand dollars are found in coastal waters all over the world. People often collect them for their beauty, and the shells are also commonly found in decorative sea-themed art.

A sand dollar is a type of burrowing sea urchin belonging to the order Clypeasteroida. They are characterized by their flat, round bodies and intricate patterns. Sand dollars live on the ocean floor in sandy or muddy areas and are found in both temperate and tropical waters. They feed on microscopic organisms in the sand, which they sift through their spines.

Sand dollars reproduce by releasing eggs and sperm into the water, a process known as broadcast spawning. This typically occurs during spring and summer when the water temperature rises. Fertilized eggs develop into free-swimming larvae, which eventually settle on the ocean floor and metamorphose into the adult form.

Yes, sand dollars are indeed alive, although the ones commonly found on beaches are often dead. A living sand dollar is covered in tiny, velvety spines and has a dark color, usually ranging from purple to brown. Dead sand dollars are bleached white by the sun and have no spines, which is the state in which they are most often collected by beachgoers.

The lifespan of a sand dollar can vary depending on species and environmental conditions, but on average, they live six to ten years. They grow from larval stage to adult size in about one to two years, reaching sexual maturity shortly thereafter, which allows them to contribute to the population's sustainability.

Sand dollars play a significant role in their ecosystem by recycling nutrients and helping to aerate the ocean floor. As they burrow and feed, they break down organic material, which promotes the decomposition process and nutrient cycling. This activity benefits other marine organisms and contributes to the overall health of the ocean ecosystem.

Legality of collecting sand dollars varies by location and is subject to local conservation laws. In many places, it is legal to collect dead sand dollars, but live ones should be left undisturbed to preserve their populations. Always check local regulations before collecting, and if permitted, only take sand dollars that are white with no spines, indicating they are no longer alive.