There is a (VIDEO) on Facebook where the fish starts to flail around despite no heart or internal organs.

What causes the fish to flail around the way it does?

My theories:

  • It is because of pressure causing the muscles to contract - much like when you leave your own hand loose and squeeze up your arm making your fingers curl.
  • It is because the nerves are still alive - much like how you can rub the fish heart the right way and cause it to beat again even though the fish is very much dead. (I watched my fifth-grade teacher do this in class)
  • 1
    $\begingroup$ I had actually heard a research talk related to this. It happens because of spinal reflex. $\endgroup$
    Sep 5, 2015 at 13:12

1 Answer 1


It is a widely known spinal reflex arc which causes decapitated animals (even soldier without head) to move over some period of time after decapitation.

One of the arc representations:

enter image description here

see also The life after decapitation

additional video


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