Sand Dollars

The sun-bleached skeletons we know them by represent a strange‚ simple life

By Candice Dyer

S and dollars have more in common with people than you might think. Scientists have discovered that the genomes of humans and sea urchins bear notable similarities; they’re our closer kin than beetles‚ crabs‚ or clams. But in most ways they’re entirely foreign. “If you want to be a stickler‚ their proper name is the five keyhole urchin‚ in the family of echinoderms‚ Latin for ‘spiny skin‚’” says Ben Carswell‚ director of conservation for the Jekyll Island Authority. “But most people‚ even naturalists‚ still call them sand dollars.” They breed by broadcasting‚ in which males and females release thousands of sperm and eggs into the water‚ which connect and develop into larvae. Thread-like appendages called cilia help the larvae move and burrow into the sand. When threatened‚ baby sand dollars clone themselves‚ a sort of evolutionary insurance. These radial discs are abundant on Jekyll‚ especially between tides‚ when they might turn up by the half dozen within a few square feet. If you are beachcombing and pick up a brown one with tiny tube-like feet that feel like velvet fur on its underside‚ it is alive‚ and you are encouraged not to disturb it. “We want to send the message not to be wasteful of a life just because it’s a simple life‚ and they are fragile when they’re alive‚” Carswell says. However, visitors are welcome to make souvenirs of the calcium-based skeletons‚ which are smooth‚ white‚ and brittle. Living sand dollars spend their days tunneling into the sand and using their feet to sweep organic matter and single-celled organisms into their mouths. They in turn are preyed upon by fish‚ crabs‚ gulls‚ and rays. “Sand dollars are an important food resource‚” Carswell says—but don’t be fooled by their cookie-like shape. “So far I’ve never heard of anyone using them as bait.”