Sunday, 18 November 2012

CAN STARFISH GROW BACK THEIR ARMS?


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Starfish (also known as Sea Stars) belong to the phylum Echinodermata, and are therefore  related to sea urchins and sea cucumbers. There are over 1,800 species of starfish and they vary considerably. Starfish and Sea Stars belong to the class Asteroidea, whilst Brittle Stars or Basket Stars are ophiuroids.  


They are all marine creatures, although some live in the intertidal zone, some in deep water, some in tropical areas and some in cold water. These radially symmetrical animals typically have a central disc body and five arms (or multiples thereof). 

Some, but not all, species of starfish can regrow a new limb given time. Some species can even regrow a new central disc from a single arm, therefore creating a whole new starfish.  This is because Starfish house most of their vital organs in their arms. The arm lives off its stored nutrients until it regrows a disc (and mouth) and is able to feed again. However, often part of the central body is required to be joined to the arm.


This fragmentation is often used to evade predators or as an escape response. If a star fish is threatened by a predator it can drop an arm, get away and grow a new arm. It often takes a starfish several months or even years to carry out this regeneration, and they are vulnerable to infections during this stage.

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