The Kid Should See This

What do sand dollars look like when they’re alive?

Pristine white sand dollars have long been the souvenir to commemorate a successful day at the beach. But most people who pick them up don’t realize that they’ve collected the skeleton of an animal, washed up at the end of a long life.

As it turns out, scientists say there’s a lot to be said about a sand dollar’s life. That skeleton — also known as a test — is really a tool, a remarkable feat of engineering that allows sand dollars to thrive on the shifting bottom of the sandy seafloor, an environment that most other sea creatures find inhospitable.

And on the seafloor sand dollars look very different. These flat sea urchins have thousands of purple spines and tube feet that help them catch food, absorb oxygen from the water, and move around. You can see their signature flower pattern, called a petaloid, in the furry-looking image below. It’s the same “five-point body plan” seen on starfish and other sea urchins.

living sand dollars sea urchin
sand dollars starfish sea urchin comparison
This fascinating Deep Look episode, A Sand Dollar’s Breakfast is Totally Metal, gets an up-close at their skills, including how they use grains of magnetite to keep them stationary in the water currents.

Follow this with the differences between a living and a dead sand dollar and a pacific razor clam burrows rapidly into the sand.

Plus: More from Deep Look, another video about magnetite in sand, and more sea urchins, including the alien-like Diadema setosum.

🌈 Related videos

Roly Polies Came From the Sea to Conquer the Earth

Rion Nakaya

Why do Leafcutter Ants cut leaves and carry them away?

Rion Nakaya

The Hidden Perils of Permafrost – Deep Look

Rion Nakaya

Pygmy Seahorses: Masters of vibrantly-colored coral camouflage

Rion Nakaya

When Your Job Is Saving The Ocean | How She Works

Rion Nakaya

Banana Slugs and Secret of the Slime – Deep Look

Rion Nakaya

The largest sea star in the world: a sunflower sea star eating

Rion Nakaya

The Fantastic Fur of Sea Otters – Deep Look

Rion Nakaya

The Crazy Cribs of Parasitic Wasps

Rion Nakaya

 
Browse the TKSST Video Collections

Get 7 smart videos delivered every week.

 

Subscribe