There are about 500 species of sea urchins worldwide, but the major commercially valuable species in the United States are the red, green and purple sea urchins. The spherical echinoderms have a hard, spiny shell called a “test,” which contains a star-shaped mass comprising five skeins of gonads (in males) or roe (females); both are marketed as roe. The sushi designation uni is also widely used, because the Japanese are major urchin consumers. All three urchin species are harvested on the U.S. Pacific Coast; red and purple are found from Baja, California to Alaska, and greens are taken from Washington to Alaska. Only green urchins are commercially harvested on the Atlantic Coast, from eastern Canada to Cape Cod. The largest U.S. producers are California (red urchins) and Maine (green urchins). Most product winds up in Japan. West Cost urchins are harvested by divers. East Coast urchins are taken by diving and trawling.