ALEXIS ROSENFELD / SCIENCE PHOTO LIBRARY ALEXIS ROSENFELD / SCIENCE PHOTO LIBRARY
Diadema urchin (Diadema setosum) on coral. This sea urchin is found on reefs in the tropical Indo- Pacific region. It is usually black and has long spines (up to 30 centimetres long), and a shell up to 9 centimetres across. Stepping on it causes a painful wound. This is a social sea urchin that forms dense groups. A sea urchin is a marine echinoderm invertebrate, related to the starfish. Like a starfish it has radial symmetry. Its shell can be thought of as 5 fused arms. An urchin uses tube feet on its underside to crawl over rocks. The mouth is also on the underside, and has five jaws that scrape up algae growing on the rock surface. Photographed in the Red Sea.
Model release not required. Property release not required.