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 largest sea star in the PNW. A voracious and speedy carnivore. Sometimes found in very dense aggregations in the shallows of mainland inlets such as Howe Sound and Indian Arm, BC. These clustered stars have been found to be feeding on barnacles and mussels and seem 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, violet 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 L and you'll see a single arm being autotomized. The next image (M) 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 a quickly-gained meal.
Copyright © 2013 All rights reserved.