Living Sand Dollars Are Beautiful On Top, And Horrifying On The Bottom!

One of the best parts of going to the beach is exploring the sand and finding hidden treasures. One of my favorites was always sand dollars. I loved the star on their backs and their beautiful white coloring.

Stack of Sand dollars - Kids Activities Blog
I just love sand dollars!

What are Sand Dollars?

White Sand Dollars are their common name but they are also known as sea biscuits or sea cookies. These sand dollars are living breathing sea urchins (like sea cucumbers) that have a design on the top of 5 petal-shapes called a petaloid. Have you ever thought of the bleached rigid skeleton as a live sand dollar?

Most of the time we think of sand dollars for decorative purposes. You may have found an intact sand dollar on a beach or even bought one at souvenir shops! But they are so much more than what looks like dollar coins. These marine animal specimens live on the sandy seafloor as a part of marine animal life.

These eccentric sand dollars exhibit a petaloid which is an ambulacrum which is an area where rows of tube feet are arranged through tiny holes in the rigid flat disc body that look like small spines. The tube feet (also called podia) are used to move, feed and breathe on the ocean floor.

The holes that go through the sand dollar’s body are called lunules and they help the sand dollar stay on the bottom of the ocean by allowing water to drain through the holes and they also act as sediment sifters.

On the bottom side there is a mouth in the center with 5 branching food grooves of tube feet.

What is the average life span of a sand dollar?

“Scientists can age a sand dollar by counting the growth rings on the plates of the exoskeleton. Sand dollars usually live six to 10 years.”

Monterey Bay Aquarium

How cool that you can determine the age of a sand dollar the way rings can tell the age of a tree stump!

What is a Sand Dollars Purpose?

A sand dollar is an animal! We are most familiar with what they look like after they die (dead sand dollars) and their exoskeletons get washed up on the beach. They were called sand dollars because they looked like old currency.

Sand Dollar Living Habitat

Sand Dollars live in shallower ocean waters just beneath the surface of sandy or muddy areas like shallow coastal waters are their natural habitat. They like warm waters, but some species can be found in deeper, cooler areas.

What Do Sand Dollars Eat?

Sand dollars eat Crustacean larvae, small copepods, detritus, diatoms, algae according to the Monterey Bay Aquarium.

What a Live Sand Dollar Looks Like

Turns out, living sand dollars are actually dark purple.

You can kinda see it here in this picture, but in real life the colors are much brighter…

What Sand Dollars Really Look Like - Kids Activities Blog

Watch Great Video of the Bottom of a Sand Dollar

When they first die, they start to fade, but retain that star shape.

But when they’re alive? They’re still so pretty.

Until you flip them over.

What Does the Underside of a Sand Dollar Look Like?

Apparently the underside of a sand dollar is where nightmares come from.

The bottom of a sand dollar has hundreds of wiggling flanges that move food toward their mouth at the center…that hole we see on the bottom.

Seriously, you have to see what these things look like!

What a Sand Dollar Looks Like After It Dies

Sadly, until today I never realized that that’s what a sand dollar looks like after it dies.

sand dollar in the sand from the top
This is what we think of Sand Dollars looking like!

Also, just because it’s pretty darn amazing, here’s what’s inside a sand dollar…they look like little doves!

Inside a sand dollar

What is Inside a Sand Dollar?

Once a sand dollar has died, floated to the top of the water or gotten washed up on a beach and been bleached in the sun, you can snap them in two and inside are butterfly or dove shapes that are pretty cool. Check out this video starting at 2:24 to see what it looks like.

diagram of what a sand dollar looks like and the different parts of the sand dollar anatomy
The anatomy of a sand dollar

Sand Dollar FAQ

What does finding a sand dollar mean?

There are legends around finding a sand dollar. Some believed that they were mermaid coins and others tell a story about how it represents the wounds of Christ on the cross and when you open them 5 doves are released.

Can a sand dollar hurt you?

No, sand dollars even when alive are harmless to people.

Why is it illegal to take a sand dollar?

It is illegal in most places to take a living sand dollar from its habitat. Check with the area you are visiting about the laws regarding dead sand dollars.

How much is a real sand dollar?

Sand dollars got their name because of their shape, not their worth!

Does something live in a sand dollar?

The whole sand dollar is an animal!

More Ocean Fun from Kids Activities Blog

Unfortunately we can’t always be at the beach hunting sand dollars and other ocean treasures, but there are things inspired by the ocean that we can do at home:

more to see

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