• Question: Why does the starfish regenerate its arms? Does it have special muscles that regenerate? Please explain thoroughly how it happens!

    Asked by tamarakacsala to Common starfish on 2 Dec 2017.
    • Photo: Common Starfish

      Common Starfish answered on 2 Dec 2017:


      Starfish can “autotomise” arms if they are attacked by predator (e.g. crab) – so losing an arm is something that starfish do to avoid being eaten. Having lost an arm, they need to regenerate it because they need 5 arms to move and feed effectively. If they lost an arm but didn’t regenerate it and then they lost another arm then they would struggle to feed. They feed by using their arms pull apart the valves of their prey (mussels) and to do that effectively they need all their arms intact. They could still do it with 4 arms but if they only had 3 arms they would probably struggle to feed on mussels.

      When they regenerate an arm, all of the tissues are regenerated, including skeletal tissue, muscles, digestive glands and nervous tissue. The radial nerve cords that run along the underside of each arm are important in controlling the process of regeneration. If we could identify molecules that the nerve cords secrete to promote regeneration, this could be useful from a medical perspective. Sequencing the entire genome of the common starfish (Asterias rubens) would help to identify these molecules … and many other things about the fascinating biology of starfish.

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