Pycnopodia helianthoides (Brandt, 1835)
Up to 20 or more soft, flexible arms (a sample of 36 had an average of 18 arms). Bright orange to purplish. To 1 m (39 in) across and weighing up to 5 kg (11 lb).
Unalaska, Aleutian Islands to southern California; intertidal to 314 m (1,038 ft).
The SUNFLOWER STAR is a formidable carnivore and one of the largest sea stars in the world.
Prior to the autumn of 2013 (when Sea Star Wasting Disease appeared) the SUNFLOWER STAR was sometimes found in very dense aggregations in Howe Sound, BC, during the winter. In this image there are approximately 12 stars per square metre. They congregated to eat barnacles and mussels but also appeared to become less active at this time.
This close-up view shows the underside of an arm. Note the four rows of tube-feet, the white spines surrounded by wreaths of pincers and the clusters of transparent gills.
Newly settled SUNFLOWER STARS have 5 arms. Soon a sixth arm sprouts and subsequent new arms sprout in pairs on either side of the sixth arm.
A SUNFLOWER STAR attacks a RED SEA URCHIN. This large urchin fought back with its long, sharp spines and stalked pedicellariae and managed to escape.
SUNFLOWER STARS are proficient diggers, often excavating deep pits to capture clams.
When I examined this SUNFLOWER STAR to see what it was eating I discovered the partly digested remains of a GIANT PINK STAR.
This view of the oral side shows the cardiac stomach partly everted. It is actually much larger than this and can envelop and digest big prey outside of the body of the star.
When a NORTHERN ABALONE is attacked it responds by twisting its shell side-to-side and rapidly gliding away from the attacker. If it doesn't respond quickly enough and the star gets a good grip with its tube-feet, it's game over.
The GIANT SEA CUCUMBER responds to attack by strongly writhing its elongate body. The cucumber has a smooth, slippery skin making it hard for the SUNFLOWER STAR to get a grip. The escape response is very effective and the cucumber is rarely caught.
NUTTALL'S COCKLE exhibits a dramatic response when attacked. The clam's muscular, finger-shaped foot suddenly emerges and acts like a powerful lever to "pole-vault" the clam away from danger. This must happen fast, for if the SUNFLOWER STAR gets a firm grip on the clam's shell, it's a seafood dinner for the star.
Attacked by a MORNING SUN STAR (left), a SUNFLOWER STAR beats a hasty retreat, but leaves behind the arm in the grip of the attacker. The SUNFLOWER STAR can deliberately cast off an arm in order to make good its escape.
The cast off arm can been seen in the grasp of the MORNING SUN STAR. It gets a meal; the SUNFLOWER STAR escapes with its life.
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The largest sea star in the PNW. A voracious and speedy carnivore. Prior to the outbreak of Sea Star Wasting Disease (SSWD) in the summer of 2013 it was found in very dense aggregations in the shallows of mainland inlets such as Howe Sound and Indian Arm, BC. These clustered stars had been found to be feeding on barnacles and mussels and seemed to enter a state of low activity during the cold winter months.
Without question this is the “king” of Pacific coast sea stars and one of the largest stars in the world. Unlike most, it has a soft, flexible skeleton that gives it surprising agility. The SUNFLOWER STAR is also "quick on its tube-feet," capable of sprinting at up to 2.1 m/min (6.9 ft/min), runner-up only to the “Olympic” champion, the SAND STAR. The number of tube-feet possessed by a large specimen is reportedly 20,000 or more.
When the SUNFLOWER STAR first settles from the plankton to live on the sea floor it has five arms just like most other stars. As it grows, additional arms sprout quickly, ultimately ending up with as many as 20 or more gracefully tapering arms radiating from its broad central disc. All those arms and bulky body require the SUNFLOWER STAR to feed often and on lots of different prey. But having more arms can also be a distinct advantage when attacking fast-moving or elusive quarry.
An extremely active and powerful predator, the SUNFLOWER STAR is equally at home on rocky reefs or sandy bottoms. In many habitats it is the most conspicuous and abundant invertebrate creature. It varies in colour from reddish orange to yellow, brown and shades of purple.
The SUNFLOWER STAR eats just about anything in its path. Its prey include green and red sea urchins, clams dug from sandy substrates by excavating large pits, scallops, abalone, snails, barnacles and occasionally, other sea stars. This star has a very large, eversible cardiac stomach that can envelop and digest prey outside its body.
Several creatures exhibit striking escape responses when attacked by a hunting SUNFLOWER STAR The NORTHERN ABALONE twists its shell violently and glides away on its muscular foot; the GIANT SEA CUCUMBER writhes spasmodically and wrestles free; the SPINY PINK SCALLOP claps its shells together to swim from danger and the GIANT NUDIBRANCH thrashes vigorously from side to side to propel itself out of range. The NUTTALL'S COCKLE exhibits an extraordinary escape response, extending its spring-like muscular foot and forcefully pole-vaulting itself away from the predator.
When attacked by the MORNING SUN STAR, the SUNFLOWER STAR can deliberately cast off (a process known as autotomy) an entire ray, making good its escape by sacrificing a single ray to the predator. This ability is possible due to specialized connective tissue that can rapidly change its tensile strength. Look carefully at picture 12 and you'll see a single arm being autotomized. The next image shows the MORNING SUN STAR engulfing its "piece" of the SUNFLOWER STAR.
Despite its far superior speed, I have found that the SUNFLOWER STAR is quite often the subject of successful attacks by the MORNING SUN STAR. In some ways the former is the ideal prey for the MORNING SUN STAR, which does not have to capture an entire, fast-moving SUNFLOWER STAR. It only has to harass it enough that the prey drops a single arm and it has an easily-gained meal.