These sea stars, commonly called starfish, are really bizarre creatures.
They have a very unique body structure unlike any other animal on earth. The cushion star looks like a foot-wide pin cushion, and they can be red, yellow, tan or purple.
This sea star is similar to the standard starfish that has five arms, but the arms are wider and have fused together to make a hard outer skeleton.
On the underside of the cushion star they have five rows of tube feet that radiate out from a central mouth. They do not have a head, brain or heart like most animals, and their bodies have water-filled canals and a water vascular system.
They take water from inside their body and move it out of tiny, hollow, tube feet on their underside, which allows them to move about the coral reef. If you flip one over it can move all of the water in its body to one side and flip back upright.
The other very-unique thing about the cushion star is it method of feeding. Like other species of starfish, the cushion star eats live coral by everting their stomach out of their body onto the live coral to digest the soft coral polyps.
Cushion stars have males and females, and they broadcast spawn by shooting eggs and sperm up into the water column at the same time, were fertilization takes place. The tiny larvae drift with the currents until they find a suitable place to settle down on the reef and grow.
Out of all of my many scuba dives in Hawai‘i I have rarely seen more then one of these colorful and unique sea stars on an hour-long dive, so they are not very common. But they are very easy to spot due to their bright colors. I have also never seen a predator try to eat one, so maybe they produce toxic chemicals like other colorful reef creatures do.
You can see the cushion star in action in the movie “The World’s Guide to Hawaiian Reef Creatures” on the underwater educational web page at underwater2web.com.
Aloha from under the surf.
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Terry Lilley, a marine biologist, lives in Hanalei. His websites include underwater2web.com and www.gofundme.com/5urrm4zw.
