Rose Star – No Two Alike

By The Marine Detective on June 5, 2020

One species. So many colours.

That’s beauty. That’s biology.

Rose Stars have such diversity in colour and pattern, that the species is also known as the “Snowflake Star”; a name suggesting that no two are alike.

Am I trying to make some sort of point as it applies much more broadly? Why, whatever would make you think that? 😉

Surely we humans rejoice in the beauty of diversity?

Please see additional photos (and slideshow) below to get a further sense of the diversity, the beauty, and the perfection.

Species information:

• Crossaster papposus to 34 cm but in British Columbia the maximum size is believed to be 17 cm.
• They can live to at least age 20. Species is slow growing. Maximum size is reached around age 10.
• Even the number of arms varies. Most Rose Stars have 11 arms but number ranges from 8 to 16. From personal communication with zoologist Neil McDaniel: ” I did counts of 63 images I had on file [all from British  Columbia’ and nearly 90% (87%) had 11 arms, about 10% had 10 and 3% had 12.”
• They are SPEEDY! Zoologist Neil McDaniel clocked them at 50 cm/min. Larger individuals were documented to travel over 5 meters in 12 hours. They are serious predators but may also be speedy because they are known to be prey for Sunflower Stars and Morning Sun Stars.
• Diet is known to include sea pens, nudibranchs, bryozoans, bivalves (e.g. clams), juvenile urchins and tunicates. Their diet is likely broader than this as they are not picky eaters. I often see them in rocky habitats covered by coralline algae species (see photo below) and believe that is, at least in part, because the prey there include Orange Social Tunicates. They are one of the few species of sea star known to feed on nudibranchs. They also are known to have attacked other sea star species – Mottled Stars and Six-rayed Stars
• How they feed: When they feel their prey, and are hungry, they retract their sensory tube feet (tube feet at the tips of their arms), and then stretch up on their tippy toes (extending their terminal tube feet) to be higher and able to “pounce” on their prey when on the ocean bottom. Smaller prey are swallowed whole. Larger prey are held with the tube feet and, as is the case with other sea star species too, they evert their stomach OUT OF THEIR BODIES and into or over their prey.
• Research supports that Rose Stars can sense potential prey and other sea stars by smell (distance chemoreception).
• In the photos below you will also see the intricacy of the surface of sea stars. You will see:
  • Spines
  • Pedicellaria = amazing little structures that can nip off the tube feet of other species of sea star e.g. the predatory Morning Sun Star (Solaster dawsoni).
  • The tufts are “papulae”. They are the gills / respiratory organs of the sea star. They can retract into the surface of the sea star’s body.
• Range: Bering Sea to Puget Sound; Arctic Ocean, North Atlantic Ocean, North Sea, western Baltic Sea.
• Depth: Found from the shallows of the intertidal to ~1,200 m. Believed to more often be in low current areas.
• I saw little impact on this species from Sea Star Wasting Disease around NE Vancouver Island BUT Rose Stars were hit very badly in 2014 in other areas e.g. Sechelt Inlet, British Columbia (McDaniel, pers. comm.). See photo at the end of the blog. The species seems to be rebounding, unlikely Sunflower Stars which remain devastated across their range.

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The next 3 images are of the same individual.

Slideshow:

Sources: 

• Lambert, Philip; Sea Stars of British Columbia, Southeast Alaska, and Puget Sound
• McDaniel, Neil, pers. comm. 2020-06-06
• McDaniel, Neil; Sea Stars of the Pacific Northwest
• Sloan NA, Northway S. 1982. Chemoreception by the asteroid Crossaster papposus (L). J Exp Mar Biol Ecol 61:85–98.
• Wallawalla.edu; Crossaster papposus