Sunflower Sea Star (Pycnopodia helianthoides)

Recently, scientists have identified the culprit behind the mass die-offs of sunflower starfish since 2013. Over 5 billion sunflower starfish are estimated to have died due to a mysterious disease. The disease is caused by a bacterium called Vibrio pectenicida. This discovery sheds light on the ongoing devastation of this important marine species along the Pacific coast of North America.

About the Sunflower Sea Star

The Sunflower Sea Star, or Pycnopodia helianthoides, is one of the largest and fastest species of sea stars in the world, with unique features and significant ecological importance.

Key Characteristics of Sunflower Sea Stars

• Size & Speed: They are among the largest sea stars, capable of moving quickly compared to other species.

• Arms: They have between 15 to 24 arms, the highest number of arms in any sea star species. Most other sea stars have between 5 and 14 arms.

• Radial Symmetry: Their body exhibits radial symmetry, a common feature in most sea stars, which helps them to move and feed efficiently.

Habitat & Distribution

• Habitat: They are typically found on a variety of substrates including mud, sand, gravel, boulders, and rock.

• Depth Range: Their usual habitat is found between intertidal coastal waters and up to 435 meters deep, though most live within 120 meters of depth.

• Geographic Range: Sunflower sea stars are distributed along the Pacific coast of North America, from Alaska down to Mexico.

Behavior and Reproduction

• Regeneration: Sunflower sea stars have the remarkable ability to regenerate lost arms, a defense mechanism when they are attacked by predators. If an arm is detached and includes part of the central disk, a new sea star can form.

• Reproduction: They exhibit external fertilization, where eggs and sperm are released into the water for broadcast fertilization. The breeding period generally spans from March to July.

Diet and Ecological Role

• Carnivorous: They primarily feed on mussels, sea urchins, fish, crustaceans, and other marine invertebrates.

• Ecological Importance: Sunflower sea stars are opportunistic hunters and play a vital role in regulating ecosystems. They are key predators of sea urchins, which in turn graze on kelp. By keeping sea urchin populations in check, sunflower sea stars help maintain the health of kelp forests, which are crucial ecosystems that provide food and shelter for many marine species.