Common name: Sunflower Star
Scientific name: Pycnopodia helianthoides
Size range: Up to 1 m (about 39 inches) across
The Sunflower Star is the largest sea star in the world, and is also known as one of the fastest. Even out of water, it comes only a close second to the Sand Star in terms of speed. Its speedy movements are courtesy of the fast-moving tube feet located underneath the sea star’s arms. It can have up to twenty or more arms. The Sunflower Star is usually bright orange or purple in colour.
Sunflower Stars are abundantly found on rocky shores, but can also be seen in intertidal zones and in deeper waters where they inhabit the sea floor. It’s also not an uncommon sight to see them clinging to piers with other sea stars.
Sunflower Stars are very voracious eaters. Given their size, they have to eat substantial amounts of food. And thanks to their flexible skeleton, they can eat almost anything. Sunflower Stars provoke many interesting escape reactions from their prey; sea cucumbers wrestle the star to get away, swimming scallops flap their shells together to flee, and Nuttall Cockles use their foot to vault away from the predator.
There are only a few animals that prey on Sunflower Stars; the Alaskan King crab (Paralithodes camschaticus) , sea otters (Enhydra lutris) and gulls (Laridae spp.). It is more commonly food shortage that reduces the numbers of adult Sunflower Stars, although filter-feeding organisms feed on them while they are in their larval stages.
Sunflower Star eggs turn into bilateral swimming larvae, which remain among the plankton for no more than 10 weeks. When they metamorphose on the sea floor, they resemble 5-armed sea stars. Additional arms are added during the course of the juvenile sea star’s life. They have external fertilization and two sexes.