Sunflower seastar

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Sunflower seastar
Sun flower sea star in tide pools.jpg
Scientific classification
Kingdom: Animalia
Phylum: Echinodermata
Class: Asteroidea
Order: Forcipulatida
Family: Asteriidae
Genus: Pycnopodia
Species: P. helianthoides
Binomial name
Pycnopodia helianthoides
Brandt, 1835 [1]

Pycnopodia helianthoides, commonly known as the sunflower seastar, is a large sea star found in the northeast Pacific. It is among the largest sea stars in the world (but not quite the largest), with a maximum armspan of 1 m (3.3 ft). Sunflower seastars usually have 16 to 24 limbs; their color can vary widely. They are predatory, feeding mostly on sea urchins, clams, snails, and other small invertebrates.

Description[edit]

Sunflower seastars can grow to have an arm span of 1 m (3.3 ft) in diameter.[2] Their color ranges from bright orange, yellow and red to brown and sometimes to purple, with soft, velvet-textured bodies and 16 to 24 arms with powerful suckers.[2][3] Most sea star species have a mesh-like skeleton to protect their internal organs.[4]

Distribution and habitat[edit]

Sunflower seastars are common in the northeast 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[5] or kelp.[6] They do not venture into high- and mid-tide areas because their body structure is fleshy and requires water to support it.[7]

Ecology[edit]

Sunflower seastars are quick, efficient hunters, moving at a speed of 1 m/min (3.3 ft/min) using 15,000 tube feet which lie on the undersides of their bodies.[2][3] 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 on dead or dying squid.[8] Although the sunflower seastar can greatly extend its mouth, for larger prey, the stomach can extend outside the mouth to digest prey, such as gastropods like abalone.[9]

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]

Underside of a sunflower seastar

Reproduction[edit]

Sunflower seastars can reproduce either asexually through fissiparity or sexually through broadcast spawning.[10] They also have separate sexes.[9] Sunflower seastars breed from May through June. In preparing to spawn, they arch up using a dozen or so arms to hoist their fleshy central mass free of the seafloor and release gametes into the water for external fertilization.[9] The microscopic sea star larvae float and feed near the surface for 2 to 10 weeks. After the planktonic larval period, the larvae settle to the bottom and transform into juveniles.[4] Juvenile sunflower seastars begin life with five arms, and grow the rest as they mature.[8] The lifespans of most seastars is three to five years.

In popular culture[edit]

Their feeding behavior was filmed for the BBC in the 2006 nature documentary Planet Earth and again in 2009 for Life.

References[edit]

  1. ^ "Pycnopodia helianthoides". Integrated Taxonomic Information System. Retrieved 9 April 2007. 
  2. ^ a b c d e Sunflower seastar - NOAA
  3. ^ a b Telnack, Jennifer. Intertidal Marine Invertebrates of the South Puget Sound, NW Marine Life.
  4. ^ a b c d Sunflowerstar. Scott Boyd's Emerald Sea Photography.
  5. ^ North Coast Intertidal Guide: Seastars & Urchins, Humboldt State University. Arcata, CA.
  6. ^ Sunflower Star. Channel Islands National Park. National Park Service.
  7. ^ Sunflower Star. North Island Explorer.
  8. ^ a b Monterey Bay Aquarium: Online Field Guide - Sunflower star. Monterey Bay Aquarium.
  9. ^ a b c Sea stars and relatives, Edmonds Discovery Programs, City of Edmonds, Washington.
  10. ^ Aaron Shepard. "Pycnopodia helianthoides, The Sunflower Star". Evergreen State College. Retrieved 28 February 2012. 

External links[edit]