Sea urchin

Sea urchins or urchins are small, spiny, globular animals with round spiny shell, typically from 3 to 10 cm across. Common colors include black and dull shades of green, olive, brown, purple, and red. They feed mostly on algae. Their "roe" is a delicacy in many cuisines. The name "urchin" is an old name for the round spiny hedgehogs that sea urchins resemble.