Oops, my starfish has lost an arm | Global Ideas | DW | 24.07.2017
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Global Ideas

Oops, my starfish has lost an arm

If you think starfish are just five-armed creatures of the deep that hover over the ocean floor, think again. They are name-defying, biologically brilliant, and full of surprises. Quite literally.

Like koala bears and flying dragons, starfish are among the ranks of misnamed animals - because they are not, in fact, fish. Also known as sea stars, they are actually echinoderms who are at home on the ocean bed with their cousins the sea urchin and sand dollars.

These beautiful marine animals, of which there are some 1,800 species, usually have five "arms,"- although some rare breeds have up to 40 - attached to a central disc.  And it is these appendages that harbor a wonderful secret. 

Although their bony skin means they don't have hundreds of predators, there are some sea dwellers with a particular taste for their unique crunch. One way they deal with this danger is to sacrifice a limb. The loss of one being better than the loss of five. Sad four-armed starfish? Only temporarily, for what gets lost to the hungry jaws of a manta ray, can regenerate.

A brilliant bright red starfish wish white spots

The central disc from which each arm protrudes is key to its regeneration

What sorcery is this, you may ask? It takes around a year for the missing arm to fully regrow, but that is not all. The severed limb, provided it has not been eaten and split from the starfish taking a portion of the central disc with it, is capable of the Lazarus-like feat of regrowing an entire body. 

So, the next time you go to the beach and come across the small calcified arm of a sea creature, throw it back into the ocean. It might just transform become something altogether more complete, and perhaps as endearing as our favorite animated marine character, Patrick Starfish.