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