Twinkle, Twinkle Brittle Star

Photo Courtesy Wikipedia.com

Isn’t this critter cute?  There are many Hawaiian names for star, but to the best of our knowledge this one was researched and we found Hoku Kai to be the most accurate.  The above picture of a cute brittle star was taken off the Kona coast.  The other picture is of a fossil, which researchers determined to be from the time when dinosaurs roamed the earth.  Earliest fossils date this species back about 500 million years when they first appeared.  A brittle star’s skeleton is made up of embedded ossicles. 

Probably of little or no food value could be the main reason that not much information can be found as far as Hawaiiana is concerned.

These animals are in the echinoderm family, which makes them related to sea urchins.  Their legs are flexible and they can reach a diameter of up to 2 feet!  In some parts of the world they are known as serpent stars.  Most people still call this group starfish, but marine biologists know they are not a fish, so the correct term is sea star.

Brittle stars, like others, are voracious feeders.  Some prey, like copepods or mollusks (snails) can be eaten whole.  Others will find themselves being devoured by a everted stomach and digested outside the sea star’s body.  According to research they have two stomachs.  Some stars will find unsuspecting sleeping fish and take them out.  Brittle stars do not have an anus.  Instead, they get rid of their waste through the mouth.  WOW!  At the end of each leg there is a microscopic eye, which allows the sea star to determine light from dark.  Their terminal tube feet, according to researchers, are especially sensitive to odors. or chemicals, emitted by other animals helping the sea star find their meals, but/ they can also detect random movement and shadows.  Depending on the species, some stars have many legs and the tube feet may, or may not, have suction.  Another species we will discuss in a future posting has a pentagram shape.  The rough top surface of a star is called a aboral, or dorsal surface.  If you look closely you may notice a small white spot, almost keyhole shaped on some.  This is called a madreporite, which acts like a water filter system supplying the star with the water necessary for movement.

These animals are generally mature after one year and can then reproduce.  They normally continue to grow for up to four years and with most species there are distinct sexes, with a few exceptions of hermaphrodites and sex changes with age.  Regeneration of lost legs is commonly known with these animals, although how long the regrow process takes could not be found.  If a large enough section of the central animal is intact with a lost leg, a whole new brittle star will regrow.

I recall a story many years ago of oyster farmers who notice a sea star invasion in their ponds.  Panicked, they collected all they could find, chopped them up, and returned them back to the water.  In a few weeks time they had nothing in their growing farms but sea stars, having to collect all the stars again and take them out to deep water for disposal before starting all over!  

There are about 1500 species of brittle stars known, and all of them are predators.  Many of them are found as deep as 1600 feet, but in Hawaii there are several types seen in just inches of water when small and moving down to deeper water as they mature.  The beginner snorkeler can easily spot these beautiful and amazing creatures of the Pacific.  If you are coming to Hawaii, please put snorkeling on the top of your list.  You will have many wonderful memories of your water adventure.  

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