Posted by: floridanature | August 16, 2008

The Sand Dollar: A Measure of Wealth

It was twenty years ago, during a particularly transient time of my life, that I found myself living on an island that was washing away. My wealth then was measured in sand dollars.

The island was just off the coast of South Carolina and it was called—no kidding—Folly. It was an appropriate name, both for the rapidly eroding Folly, as well as the ambiance created by those who knew their experience on this slender spit of sea-washed sand would be as wondrously natural as it was brief.

My beach home, up on stilts, teetered just inside the lee slope of the dune. I would begin most mornings by walking out my front porch, over a narrow boardwalk that spanned the dune, and then down wooden steps to the flat, wide southern beach. In the winter, when visitors were scarce, I could hike to the desolate tip of the island without seeing another set of footprints.

Life before Folly had seemed complex and I was ready to take Emerson’s advice, to “simplify.” I did so by tuning out the man-made world, and tuning in the natural one. I started every morning by counting what was really important—-the brown pelicans soaring overhead, the bottlenose dolphins swimming in close to feed, and on the varnished beach, the fragile bleached-white skeletons of the echinoderms known as the sand dollar.

On my best sand dollar day, I counted seven. They were so common that after a while I only picked up the finest specimens to keep, stacking them in great piles back on my porch. Despite their abundance, each intact ‘dollar’ was a new surprise. I found it remarkable anything that delicate could survive the powerfully capricious Atlantic at all.

Others were similarly impressed: The city of Folly Beach, gloriously oddball as only a place that’s washing away can be, used the sand dollar as its symbol on its city crest. In the one-block long “downtown” of Folly, there was a bar named the Sand Dollar, and in a little shop next door, someone painted the tops of the flat shells with pictures of pelicans and dolphins. Plastic bags of sand dollars hung from racks there, and packed inside were little sheets of paper with “The Legend of the Sand Dollar.

The legend was a story of religious symbolism, one I would see retold again in little beach shops along the Atlantic coast, and it relied on the configuration of the “keyhole sand dollar” to work. It went something like this:

The five-pointed “star” etched in the top represents the star that drew the shepherds to the manger, the petals spreading out over the top and the bottom depict the Christmas poinsettia, and the five ‘keyholes’ are the wounds Jesus suffered on the cross. When broken open, the allegorical Cracker Jack prize tumbles out—five tiny calcium “doves” of peace and goodwill.

Even after I left Folly, the sand dollar continued to intrigue me. By the time I stumbled across my second motherlode of sand dollars not so long ago, the biology behind those stars and holes and little doves had some meaning. My companion and I, in snorkeling gear, were finning out into a splendid little cove called Fernandez Bay on the southwest edge of a remote Bahamian island called Cat. The day was glorious, and the late tropical sun low enough in the sky to cast a golden light on the clear water.

We were headed for an offshore clutch of rock and coral, passing over a monotone of white sand, a bottom shaped by the Etch A Sketch of nature’s geometry—curvatures that mimic the surface waves. The ease of the Tropics and the endless white sand mellowed me so fully that it wasn’t until we were several hundred yards offshore that the anomalies begin taking shape in the bottom.

They were round, topped with miniature stars, and bleached as ghostly white as the bottom. It was as if someone had seeded them there for us, scattering them like flat white Easter eggs. This was my old friend from Folly, the sand dollar. With some excitement, I dove down for the first one, bringing it up to show my partner, and watching as her eyes grew big behind her mask. Before the afternoon was over, we picked up a half dozen, leaving several times that many behind for others to find.

Back at our cottage on the cove, we sat on the porch and examined our treasures. We shook them and heard the five “doves” or ossicles rattling inside. If our dollars had still been alive, they would have been covered with fine purplish-brown spines. In fact, the live ones were likely just under the sand, for that is where they spend most of their time. But these were dead as doornails. The flat, gradual slope of the bottom helped keep them intact, just as it had off the Carolina coast. (By contrast, deeper seas tend to tumble and crush breakable shells like these.)

Sand dollars are a bit like foreign currency—they may look alike from a distance, but up close they vary dramatically. There are many species of dollar similar to the five-keyhole, including a six-holed version, one with four notches around the edge of the disc, and one with no holes at all. All share the same class Echinoidea with sea biscuits, heart and sea urchins. Indeed, you can think of a sand dollar as a sort of flattened urchin, for that is what it is.

While the body of the dollar seems to be one piece, it is in fact, a fine network of calcium carbonate plates tightly wedged together.

On the top between these skeletal plates are gills arranged into “petals” that allow the sand dollar to breathe. Movement is accomplished by the rowing action of spines. And as for the “keyholes”—called lunules—some scientists think they help keep the animal in place in strong currents. (In contrast, the bulky sea biscuit, which looks a bit like a dollar on steroids, sit atop the sand, disguising itself with algae, grass and shell debris.)

In sex, dollars are like most echinoderms in they are either male or female, although for us non-dollars, they are nearly impossible to tell apart. Look closely at the four tiny points at the tips of the star on top: This is where the eggs or sperm are released.

If the sex act seems lonely and brief, it is blissfully simultaneous, triggered by rising temperatures in the spring. Like coral spawning (which happens during August and September), the eggs and sperm connect in the water, and the fertilized eggs spawn free-swimming larvae. Eventually, these zooplankton metamorphose and drop to the bottom, having magically turned into miniature sand dollars.

And there they live their lives, turning bone white after death. For those of us who marvel at the little miracles of the sea, the sand dollars then become available—for symbolism, or simplicity. Or just for the pure joy of natural discovery, laying unexpected and whole in the white sand. And there’s no folly in that, after all.

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Responses

  1. This page came up as a related post to one I’ve written recently about Stars in Nature. Sand Dollars are certainly intriguing creatures.

    I’ve only ever found the smaller sea biscuits on Nova Scotia’s beaches. My sons have found beds of them while diving here, but the water is so cold that I’m not tempted to accompany them. Your sand dollar adventures in SC and the Bahamas sound like heaven to me.

    The most beautiful things in life are ephemeral. Knowing that the end is just around the corner makes each moment sweeter. So it must be in Folly (if it’s still there after your visit 20 years ago).

    • we winter in puerto vallarta, and this year there are thousands of sand dollars all over the area, as the water is receding a long way back,,,,,what i dont get is….why are people picking them up and stacking them like cookies or filling a plastic bag with them….dont they realize that they are living creatures ??? just a pet peeve that really irks me everytime i go for a walk on the beach…..

  2. Nice write up about the sand dollar and I like your banner photo. I lived in central Florida for 27 years.

  3. Hi,

    I am developing interpretive signs for Goose Spit Park, a park along a sandy spit close to Comox in British Columbia, Canada. We have a lot of sand dollars off the shores of the park and I did a short write-up of sand dollars for the interpretive sign.

    I am looking for a good photo of sand dollars and was wondering if you have the one posted on your website in high resolution and if I could get permission to use it on our signs.

    Thank you for getting back to me. Best wishes,

    Karin Albert
    Parks Planner
    Comox Valley Regional District

  4. my self reserch fellow, recently i got some sand dollars, i want your help for identification. it is possible for you.

  5. I line in Miami since 1954. Are you still posting Florida stuff?


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