Habitat: Commonly on coral reefs, in turtle grass beds, on sand or rock bottoms, and mangroves; generally in calm waters. Distribution: Caribbean to south Brazil, Gulf of Mexico and Panama. Natural History Notes: D. antillarum is highly active and capable of fast movement. It changes the color of its test in response to changes in light intensity. The species is gregarious and often occurs at high densities. An ecologically important grazer, D. antillarum regulates algal growth in reef communities and facilitates settlement of coral larvae. A massive urchin die-off in 1983 in the Caribbean resulted in loss of more than 97% of mature individuals in some areas. Recovery has been slow. The urchin's spines can transfer organic matter and bacteria and cause infection when they puncture human flesh. D. antillarum is similar morphologicallly and biochemically to D. mexicanum. Depth: 0-400m, but usually less than 50m Characteristics: This urchin has extremely long (300-400mm), fragile, slender, hollow, black spines. The adult individual can exceed 500mm in diameter. The test and spines are usually black, however some individuals have white or gray spines, and some are almost entirely white.