Sea urchins are echinoderms! Echino-what? As larvae, they have two identical halves (lateral symmetry), but as adults, they are round. They have an exoskeleton made of calcium-rich plates over an internal skeleton. Tube feet help them stick to materials and move along using suction—sea urchins even breathe through the skin of their tube feet! Their mouth is protected by cartilage and spines that also help them gather food. They use teeth to eat just about anything they can find, from algae to worms and crustaceans and everything in between!
Sea urchins are popular additions to home saltwater aquariums. To protect marine life, choose those that have been cultured by people and not collected wild from the ocean.
Up to 4 inches across, lives in northern Atlantic and Pacific Oceans plus Arctic Ocean.
IUCN Red List status: Not Evaluated
Up to 5 inches long, lives in warm waters of the Atlantic Ocean and Mediterranean Sea.
IUCN Red List status: Not Evaluated