Living only in Australia, the purple sea urchin grows to 12.5 cm across and lives on both hard and soft surfaces down to 40 m. Before becoming an adult, the urchin builds a hard shell covered in sharp spines for protection. Sea urchins have no eyes, but can detect light with their spines! They also have very impressive teeth which are self sharpening. Purple sea urchins eat into rocks and create nooks to hide from predators and strong waves. Purple sea urchins are herbivores, feeding on algae and kelp. Purple sea urchins move using many tiny legs, which they can control by pushing water in and out of them (just like seastars). Many people dive and collect urchins, as their eggs are considered a delicacy all over the world. Collecting urchins is not recommended in the Derwent due to historical heavy metal contamination. See our seafood safety section for more information.