Sea Urchins

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!