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Back You are here: Home Features Events and Features Fort Fisher Aquarium Ask the Aquarium: Question: How do sand dollars reproduce?

Ask the Aquarium: Question: How do sand dollars reproduce?

Sand dollars undergo several developmental stages before becoming the flat, round,
cookie-shaped animals we recognize. A white sand dollar is the skeleton of a once live sand dollar.

Answer. These disk-shaped animals live in colonies and reproduce by releasing eggs and sperm into the water. As a rule, when one individual begins to spawn all the others do likewise. Simultaneous spawning greatly increases the chances of fertilization and continuation of the species.
Spawning usually takes place spring through August and likely occurs multiple times. Females can produce more than 350,000 eggs per year. The fertilized eggs drift in ocean currents for many weeks as they undergo a number of developmental changes – none of which we would recognize as a sand dollar. During this time, thousands are consumed by a wide variety of sea life. Those that reach full development settle on the seafloor to become exact miniatures of their parents. Sand dollars are members of a group of animals known as echinoderms, meaning “spiny-skinned.”
Like urchins, starfish, sea cucumbers and other members of this group, sand dollars feed largely on organic matter mixed among sand grains. The mouth is on the underside of the body and contains five teeth used for grinding.
The burrowing habit of these flat, round animals makes them difficult to see in the shallow waters where they live.
Most beachgoers are familiar with the smooth, white, fragile sand dollars found washed up on beaches. These are skeletons of former live sand dollars and are considered prized finds.
Their white color comes from having been bleached by the sun. By gently shaking the fragile shell, you can often hear their five teeth rattling inside. Live sand dollars, on the other hand, are dark brown, or sometimes purplish or greenish and covered with short, nearly invisible bristly spines.
Live sand dollars should never be collected. When alive, the sand dollar’s spines are in constant motion to move it along and to enable it to burrow into sand. For a look at a live sand dollar on the move, watch a time-lapse video at youtube.com/watch?v= SRAfjvws13E. Discover more fascinating facts about North Carolina’s aquatic environments by visiting the aquariums on Roanoke Island, at Fort Fisher and at Pine Knoll Shores, or Jennette’s Pier in Nags Head.