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Starless Starfish

May 30, 2011

A starfish without arms makes scientists rethink how they classify animals.



Starless starfish…I’m Bob Hirshon and this is Science Update.

In the 1980s, researchers discovered a marine organism living on timbers that had fallen to the sea floor, nearly a mile below the surface. They thought the animal, called xyloplax, or sea daisy, represented a whole new class of echinoderms. But DNA analysis by computational biologist Dan Janies of Ohio State University and his colleagues instead revealed that xyloplax are actually a type of armless starfish.

DAN JANIES (The Ohio State University):

It’s in fact just a strange starfish.


He says the lack of arms is deceptive, but an adult xyloplax actually resembles a juvenile starfish.


What evolution has done here is truncated the life cycle. So we have a juvenile size and shape animal that has adult reproductive organs.


He says the discovery highlights the importance of using DNA to correctly classify enigmatic organisms. I’m Bob Hirshon, for AAAS, the science society.