Sea Urchins

Sea urchins are small sea animals shaped like balls. They are covered all over with sharp spines. Sea urchins live on rocks and coral in oceans all around the world. They come in many colors like purple, red, and black. They are cousins of starfish and sand dollars.

Body and Spines

A sea urchin has a hard, round shell under its spines. The spines protect it from fish and other animals. Sea urchins move slowly using tiny tube feet between their spines. Their mouth is on the bottom of their body. They eat mostly seaweed and algae.

Life on the Reef

Sea urchins help keep the ocean healthy. By eating seaweed, they stop it from covering up coral. They live in tide pools, reefs, and deep parts of the sea. Sea otters, crabs, and some fish like to eat sea urchins. When there are too few urchins, seaweed can take over.

Fun Facts

• Sea urchins have tiny teeth that keep growing.
• Some sea urchins can live for 200 years.
• Their mouth has five teeth shaped like a star.

Did You Know?

The sea urchin's mouth is called Aristotle's lantern. It was named after an old Greek thinker who first wrote about it.