Diadema antillarum, commonly known as the long-spined sea urchin, is a species found in the Caribbean Sea and the Gulf of Mexico. It is characterized by its long, slender spines that can reach up to 30 centimeters in length. This sea urchin plays a crucial role in coral reef ecosystems by grazing on algae, helping to maintain the balance between coral and algal growth. In the 1980s, Diadema antillarum populations suffered a dramatic decline due to a disease outbreak, leading to significant ecological changes in coral reefs. Conservation efforts are ongoing to restore their populations, as they are vital for the health of coral ecosystems and the overall biodiversity of marine environments.