Sea urchins are perhaps best known for their armor of spines. But their mouths may be even more daunting—urchin teeth can literally chew through stone without getting dull. (Related: "Eyeless Urchins ...

Without sea stars, an explosion of sea urchins knocked the ecosystem off balance. Now scientists are racing to breed a new generation of their predators. An ochre sea star tries to blend into a kelp ...