Sea urchins
This animal's sharp spines spear food and protect the urchin from predators. Between the spines are hundreds of tiny, sticky, tube feet.
Using their spines and teeth, urchins burrow slowly into solid rock. Because they grow as they dig, they sometimes end up trapped in holes, where they're stuck waiting for food to drift their way.
Got kelp?
Urchins love to eat kelp. Sometimes they eat so much that they destroy the kelp beds. But, sea otters love to eat urchins. A healthy sea otter population prevents the number of urchins from growing too large, and helps keep the kelp forest healthy.
Terrific tube feet
An urchin's soft feet are always busy. Some hold the urchin to rocks, while others pass kelp and other food to its mouth. An urchin also "breathes" through its tube feet—that's where gases are exchanged, instead of in gills or lungs.
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