Sunflower Star
Pycnopodia helianthoides

Physical Description

• Large sea star with fifteen to twenty-four arms.
• They have 15,000 tube feet.
• Coloration of their soft skin can be orange, pinkish, yellow, brown, and purplish with white spines.
• They can weigh up to 13.5 pounds and have a diameter over 3 feet
• Juvenile sunflower stars start life with just five arms and can have 24 by maturity.

Range

• Unalaska Island, Alaska to Baja California, Mexico.
• Less common south of Monterey Bay, California.

Habitat

• Live in sand, gravel, mud, or rocky substrates.
• Commonly found from the intertidal zone to 390 feet depth.
• Can be found as deep as 1,430 feet.

Reproduction

• When they spawn, they stand on their ray tips and release sperm and eggs over the substrate.
• The fertilized eggs become bilaterally symmetric larvae (foldable on one line of symmetry) until they are 7 weeks old, when they have metamorphosed into three-legged larvae.
• Those larvae drop onto the substrate and becomes a miniature pentaradially symmetric (foldable on five lines of symmetry) star..

Diet

• Sea urchins the majority of its diet.
• Also eat fish, mussels, barnacles, crabs, clams, sea cucumbers, gastropods, octopuses, sand dollars, abalone, snails, chitons, dead squid, occasionally sponges and algae.

Predators

• Alaskan king crabs, sea otters, gulls.

Interesting Facts

• This is the heaviest and fastest known sea star, able to move at 3.5 feet per minute!
• Unlike most sea stars with a rigid, one-piece skeleton, sunflower stars have a unique disjointed skeleton and rely on fluid pressure to maintain their form. 
• When attacking food, they use their leading eight arms to grab the food and pull it into their stomach. 

Sources: Aquarium of the Pacific; Monterey Bay Aquarium; animaldiversity.org; University of Puget Sound

Photo: Matthew Meier