| Sunflower starfish | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Forcipulatida |
| Family: | Asteriidae |
| Genus: | Pycnopodia |
| Species: | P. helianthoides |
| Binomial name | |
| Pycnopodia helianthoides Brandt, 1835 [1] |
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The sunflower sea star (Pycnopodia helianthoides) is a large predatory sea star usually with 16–24 limbs called rays. It is the largest sea star in the world. Sunflower sea stars can grow to have an arm span of 1 metre (3 ft 3 in) in diameter.[2] The color of the sunflower sea star ranges from bright orange, yellow and red to brown and sometimes to purple, with soft, velvet-textured bodies and 16–24 arms with powerful suckers.[2][3] Most sea star species have a mesh-like skeleton that protects their internal organs.[4] Easily stressed by predators such as large fish and other sea stars, they can shed arms to escape, which will grow back within a few weeks. They are preyed upon by the king crab.[4]
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Sunflower sea stars are quick, efficient hunters, moving at a speed of one metre per minute,[3] using 15,000 tube feet which lie on the undersides of the body.[2] They are commonly found around urchin barrens, as the sea urchin is a favorite food. They also eat clams, snails, abalone, sea cucumbers and other sea stars.[2] In Monterey Bay, California, they will feed upon dead or dying squid.[5] Although the sunflower sea star can greatly extend its mouth, for larger prey, the stomach can extend outside the mouth to digest prey, such as gastropods like abalone.[6] Their feeding behavior was filmed for the BBC in the 2006 nature documentary Planet Earth and again in 2009 for Life.
Sunflower sea stars can reproduce either asexually or sexually through broadcast spawning.. They also have separate sexes.[6] Sunflower sea stars breed from May through June. In preparing to spawn, they arch up using a dozen or so arms to hoist its fleshy central mass free of the seafloor and release gametes into the water for external fertilization.[6] The microscopic sea star larvae float and feed near the surface for two to ten weeks. After the planktonic larval period, the larva settles to the bottom and transforms into a juvenile sunflower starfish.[4] Juvenile sunflower sea stars begin life with five arms, and grow the rest as they mature.[5] The life span of most sea stars is 3–5 years.
Sunflower sea stars are common in the Pacific from Alaska to Southern California,[2] and are largest in Puget Sound, British Columbia and Alaska.[4] They generally inhabit low subtidal and intertidal areas rich in seaweed[7] or kelp.[8] They do not venture into high- and mid-tide areas because the body structure is fleshy and requires water to support it.[9]