The Sunflower Star is related to other sea stars, sea urchins and Sand Dollars. This unusual animal begins life with five or six arms and adds more (up to 24) with age. The large number of legs enables it to reach very large sizes, up to fifty inches (130 cm) in diameter in some cases. It has a soft, flexible surface, and is usually pink, purplish or brown in color.
Sunflower Stars are the largest and most active of the Pacific coast sea stars. They can move at a speed of four feet per minute and have 15,000 tube feet to help them along. As a result of their comparatively fast speed, they are skilled predators that feed on sea urchins and bivalves which they usually swallow whole and digest internally. When two Sunflower Stars meet, they frequently display arm movements that are thought to be combative. These interactions appear to affect the distribution and feeding activities of the population.
When challenged by predators such as large fish and crabs, this animal can shed arms in order to distract and escape. Missing limbs will grow back within a few weeks.
Sunflower Stars inhabit the low intertidal zone on rocky shores, and can be found subtidally to 1,435 feet (437 m) on rock, sand or mud. They can be found from Alaska to southern California.