Living Sand Dollar – Beautiful on top, Horrifying on the bottom
One of the best parts of going to the beach is exploring the sand and finding hidden treasures…shells, sand dollars…and more. One of my favorites was always sand dollars. I loved the star on their backs and their beautiful white coloring.
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?
Related: Sand dollar coloring pages for kids
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.
Watch this Great Video of the Bottom of a Live 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 This Underside of A Living 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 is the average life span of a live 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 Does A Sand Dollar Do?
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.
Where Do Sand Dollars Live?
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 Does A Live Sand Dollar Eat?
Sand dollars eat Crustacean larvae, small copepods, detritus, diatoms, algae according to the Monterey Bay Aquarium.
What An Alive 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 Do Sand Dollars Look Like After They Die?
Sadly, until today I never realized that that’s what a sand dollar looks like after it dies.
Also, just because it’s pretty darn amazing, here’s what’s inside a sand dollar…they look like little doves!
What is Inside A Live 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.
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 sting 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 sand dollar worth?
Sand dollars got their name because of their shape, not their worth!
What lives inside 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:
- Sand dollar craft ideas
- Flip flop craft inspired by summer days at the beach
- Ocean coloring pages
- Ocean playdough recipe
- Free printable mazes — these are ocean themed and super fun!
- Here is a huge list of kids ocean activities!
- Ocean activities for kids
- And how about some under the sea sensory ideas?
more to see
Did you learn about Sand Dollars? Did you learn anything new?