Tuesday, May 3, 2016

Eyes Under Puget Sound: Critter of the Month – The Sand Star

By: Dany Burgess & Angela Eagleston, Environmental Assessment Program

A familiar face

If you’ve ever been to an aquarium or explored a tide pool, then this Critter of the Month is no stranger to you! Luidia foliolata, also known as the Sand Star, is one of many sea star species commonly found in Puget Sound.

Luidia foliolata. Photo courtesy of Neil McDaniel.

The need for speed

L. foliolata is dull in color but makes up for its drabness in other exciting ways. It is one of the fastest sea stars in the world, traveling at speeds of over nine feet per minute! Impressive when you consider that the speed of a typical sea star is only about six inches per minute.

Like all sea stars, the underside (oral side) of the Sand Star’s arms contain thousands of tube feet, called podia, that move together to take it wherever it needs to go. However, L. foliolata’s specialized tube feet take locomotion to the next level, allowing it to obtain remarkable speeds.

Rather than the typical suction cup-like discs that most other sea stars have at the end of their tube feet, L. foliolata uses what is called a duo-gland adhesive system in its tube feet. First, it secretes a glue-like adhesive so that it can pull itself forward, then it secretes a de-adhesive so it can pick up its feet and take the next “step”.

Close-up of tube feet. Photo courtesy of Neil McDaniel.

Use it or lose it

LEFT: L. foliolata with part of one arm missing. By Jennifer Vanderhoof.
Photo courtesy of King County Marine Monitoring Program.
RIGHT: L. foliolata with regenerating tip arm.
L. foliolata can get fairly large--up to 30 cm in diameter--with five tapered arms or rays bordered by small white spines. It's not uncommon to see Sand Stars with missing limbs, or with one or more arms that are much shorter than the others.

These tiny limbs are actually brand new arms, replacing ones that were shed as a defense mechanism when the sea star was stressed or disturbed. This process is called regeneration, and it can be used to grow back multiple arms at once as long as the sea star’s central disc is not damaged and it can still eat.

Tube feet and spines surround the central mouth on the
underside of the Sand Star.

Armed and dangerous

The Sand Star is predatory in nature and uses its tube feet to bury itself in the sediment, eating whatever gets in its path during the excavation process. Unfortunately for the Sand Star, it is limited to the size of prey it can eat based on whatever fits into its tiny mouth.

Unlike other sea stars that can expel their stomachs and digest large prey items outside of their bodies, L. foliolata has to ingest its prey. It typically consumes little sea cucumbers, small clams, brittle stars and marine worms.

Critter of the Month

Our benthic taxonomists, Dany and Angela, share their discoveries by bringing us a Benthic Critter of the Month. Dany and Angela are scientists who work for the Marine Sediment Monitoring Program. These posts will give you a peek into the life of Puget Sound’s least-known inhabitants.

In each issue we will highlight one of the Sound’s many fascinating invertebrates. We’ll share details on identification, habitat, life history, and the role this critter plays in the sediment community. Can't get enough benthos? See photos from our Eyes Under Puget Sound collection on Flickr. Look for the Critter of the Month on our blog.

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