Have you heard of an animal that has nerves of steel, and literally eats metal for breakfast? This hardened, extreme creature survives where few others could, and it’s none other than the… sand dollar? Yep! And this creature has a lot to teach us about the value of adapting and evolving in the most challenging of situations.

Ever been on the beach with your family or friends, hunting for the prettiest shells you can find, and stumbled across a full sand dollar? Or half of it?

But do you actually know what one looks like when they’re alive?

There aren’t many of these unique creatures to be found, so let’s dive beneath the surface to discover the metal-eating, hardcore animals who survive in the places their ocean friends thought inhospitable.

Image: Woman in a white dress holding five sand dollars.

Source: Pixabay

When describing it to you for the first time, maybe mom or dad, grandma or grandpa called them smooth, round, or even silky. But did grandma ever call them… fuzzy? The truth is, these elusive critters look nothing like what you find in the sand at low tide. When these creatures are alive, they aren’t white. While you’d never imagine it, they’re actually grayish-purple and fuzzy!

Ok, maybe it isn’t fuzz, but it sure looks that way!

You may see these creatures all the time, but I’ll bet you never realized they’re this unique!

The “shell” you may pick up on beach day is actually the skeleton of this unique creature. And it’s a pretty cool one, at that. The structure of their skeleton is a feat of evolution that allows sand dollars to stay on the sandy seafloor, strong currents and all—a place most marine life finds inhospitable. Their “fuzz” is actually tiny spines, tube feet, and pincers!

“If you pick up any sand dollar and observe it edge-on, it looks like an airplane wing alive with a flurry of activity: tiny spines, tube feet and miniature pincers called pedicellariae that carry out various tasks.” – Amanda Heidt, KQED 1

Down on the sandy seafloor, the sand dollar has an average lifespan of 6 to 10 years, 2 and is most closely related to sea urchins. 3 Burrowing in the sand for protection and for food, 4 they stick up at all kinds of odd angles! They share the classic 5 “petals” with their cousins—sea urchins and starfish—and get this: they have no brains, just nerves. These former sea urchins evolved to be flat to reduce drag and slip through the current—just another way they’ve adapted to their harsh environment!

Ok, back up. Purple, fuzzy, metal-eating starfish relatives? This video turned my conception of this beach-comber’s prize on its head.

Not only is their look different from what you’d expect, but they are also hardcore – surviving in rough conditions and eating metal to weigh themselves down. Yeah… you read that right. As they shuffle along the seafloor on their small spines, they grab sand along the way, passing it up those spines and into the mouth. Eating the microscopic algae and bacteria on each grain, they grind up the sand but save the chunks of metal, swallowing them whole to ensure they can stay down on the seafloor without floating up or being swept away. 5

It’s impossible not to be intrigued by these nostalgic creatures. What we might have thought was a cute souvenir to sit on our desks is actually the remnant of a tough, badass burrower. Take a look at this great video from Deep Look for a window into the life of a creature who you and I probably thought we knew a lot about!

Shoutout to Deep Look for this incredible view into a habitat we don’t often get to see. For more great science and nature content, check them out! I don’t know about you, but realizing that our assumptions about creatures like the sand dollar are totally incorrect opens a whole new door to the possibilities that exist out there.

Learning to adapt to our environment!

We humans should take notes from the sand dollar and learn to evolve, too! Maybe it isn’t by slimming down to an inch wide to reduce drag or swallowing metal to keep our feet on the ground, but there is certainly something to be learned about thinking outside the box and realizing that sometimes, the odd solutions are the best ones.

Perhaps it’s thinking differently about the way we exist in this new, online world that’s been created in the last year. Maybe it’s learning more about the people around us so that we know how to best get through to them! Whatever it be, adapting to what’s around us can be nothing but helpful.

And things are not always what they seem…

I never knew that picking up a sand dollar was akin to finding a femur – you’re just picking up a skeleton that used to be so much more!

The ocean is a challenging place to study. After all, it’s much easier to send a person into space than to the bottom of the ocean. 7 We know even less about the ocean floor than we do about Mars, Venus, or the Moon, 8 and on a planet where 95% of the ocean is unexplored, 9 who knows what possibilities lie beneath the surface.

For more intriguing animals who live in the solar system’s most desolate places, check these articles out next!

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And another important thing:

Next time you stumble upon a sand dollar on the beach, here are some guidelines to help you decide if it’s ok to take it home. Often us beach-goers accidentally take sand dollars while they’re still alive, which is obviously not good. Before you take one home…

  • Hold the sand dollar and watch its spines. If they move, it’s alive. (And if it’s alive, get it back in the water, stat!)
  • Look at the color. If you’re seeing gray, brown, or purple, they’re likely alive. If they’re very white, they’re dead and ok to take home.
  • While alive, sand dollars secrete a substance that will turn your skin yellow. If you hold it and it leaves a yellow spot behind, it’s alive.

One other note: In many states, taking a live sand dollar from the beach is illegal, though laws vary about taking a dead one. “It’s best to check for signs at the beach, look at your state laws online or ask a lifeguard or warden working at the beach.” 10

Hopefully next time you’re searching for a sand dollar or stumble upon one at the beach, you’ll be able to shock your friends and family with your newfound sand dollar knowledge. And remember, if the sand dollars can evolve and adapt to crazy conditions, so can you.

Ellen

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Notes:

  1. Heidt, Amanda. “A Sand Dollar’s Breakfast Is Totally Metal.” KQED, 9 Aug. 2018, www.kqed.org/science/1932072/a-sand-dollars-breakfast-is-totally-metal. Accessed 21 July 2021.‌
  2. Monterey Bay Aquarium. “Sand Dollar.” Montereybayaquarium.org, 2021, www.montereybayaquarium.org/animals/animals-a-to-z/sand-dollar. Accessed 21 July 2021.‌
  3. “Eccentric Sand Dollar  ·  University of Puget Sound.” Www2.Pugetsound.edu, www2.pugetsound.edu/academics/academic-resources/slater-museum/exhibits/marine-panel/eccentric-sand-dollar/. Accessed 21 July 2021.‌
  4. Ables, Jessica. “Echinarachnius Parma.” Animal Diversity Web, animaldiversity.org/accounts/Echinarachnius_parma/.
  5. Heidt, Amanda. “A Sand Dollar’s Breakfast Is Totally Metal.” KQED, 9 Aug. 2018, www.kqed.org/science/1932072/a-sand-dollars-breakfast-is-totally-metal. Accessed 21 July 2021.
  6. Deep Look. “A Sand Dollar’s Breakfast Is Totally Metal | Deep Look.” YouTube, 9 Oct. 2018, www.youtube.com/watch?v=dxZdBPDNiF4. Accessed 30 Oct. 2019.‌
  7. Stillman, Dan. “NASA – Oceans: The Great Unknown.” Nasa.gov, 2012, www.nasa.gov/audience/forstudents/5-8/features/oceans-the-great-unknown-58.html.‌
  8. Copley, Jon. “Just How Little Do We Know about the Ocean Floor?” Scientific American, 9 Oct. 2014, www.scientificamerican.com/article/just-how-little-do-we-know-about-the-ocean-floor/. Accessed 13 Dec. 2019.
  9. Kershner, Kate. “Do We Really Know More about Space than the Deep Ocean?” HowStuffWorks, 7 Apr. 2015, science.howstuffworks.com/environmental/earth/oceanography/deep-ocean-exploration.htm.
  10. Hoyt, Aliya. “Is It OK to Take Sand Dollars off the Beach?” HowStuffWorks, 6 June 2019, science.howstuffworks.com/environmental/conservation/issues/sand-dollars-off-beach.htm. Accessed 22 July 2021.‌

Ellen Allerton

Sponsorship Coordinator

After graduating from St. Lawrence University in 2020 and returning home to Vermont, Ellen found that helping make the world a better place with the EWC team was just where she wanted to be. You can usually find her watching television while getting crafty, on the ice as a figure skating coach for 10-14 year old's, or in her inflatable kayak named Heidi. She’s quite the film nerd and quite the cook, and likes it best when those two things—movies and food—coincide.