Sea Urchin

ocean · spiky · slow-moving · algae eaters

Nearly 950 species. Sea urchins live in every ocean on Earth, from shallow waters near the shore down to the deep sea more than 3 miles below the surface.

Built-in armor. Their entire body is covered with sharp spines that stick out in all directions, protecting them from hungry predators like sharks and sea otters.

Tiny tube feet. Instead of legs, sea urchins have hundreds of tiny tube-like feet that let them slowly crawl and grip rocks on the ocean floor.

Algae lovers. Sea urchins spend most of their time munching on seaweed and algae, though they also eat slow animals like sponges and crinoids.

Urchin barrens. When there are too many sea urchins and not enough predators to control them, they can eat so much algae that they destroy entire underwater forests and create empty wastelands.