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Instant Zombie – Just Add Salt.

The views expressed are those of the author and are not necessarily those of Scientific American.


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Those of you who follow me on Google+, facebook or twitter might have seen this neat little video:

Yeah, it freaked me out, too. But this little cephalopod isn’t actually alive – he’s just
very freshly dead. A similar phenomenon can be seen in these frog legs:

How are these dead body parts being brought back to life?

These clever cooks are capitalizing on biology to put on a show. The key is that the muscle has to be fresh – very, very fresh. So fresh, in fact, that its neurons are still completely in tact and ready to fire.

All cells are polarized, which means the concentrations of charged atoms, called ions, of the fluid inside them is different from the fluid outside them. It is this difference in ion concentrations that creates a difference in charge (or voltage) across membrane. This difference – called a membrane potential - allows neurons to work.

Neurons are highly specialized cells which process and transmit electrical signals. When not activated, neurons maintain their membrane potential by actively pumping out sodium ions and pumping in potassium ions, keeping a voltage difference of roughly -70 milivolts. When a neuron is activated, however, specific channels open that allows sodium ions to flood in. This rapid change in the charge difference causes potassium channels to open, allowing potassium to flow out. At a certain point, the channels all close, and those active pumps work towards restoring the resting membrane potential – but not before triggering channels nearby to open. That’s how the signal moves from one end of the neuron to the other – channels open in one area, which causes channels nearby to open, and so on and so forth from one end to the other:

When a creature dies, its neurons don’t stop working right away. So long as there is still enough energy around to maintain that membrane potential, the neurons will work.

What you might have noticed is that in the case of the dancing dead, the cooks have added one key ingredient: salt (soy sauce is very salty). Salt – or sodium chloride – is chock full of sodium ions. This overwhelming dose of sodium ions is enough to trigger the still-working neurons into firing, signalling the muscles to contract.

So there you have it – take freshly killed muscle, add salt, and voila! – the dead shall rise again. Briefly, anyway.

Christie Wilcox About the Author: Christie Wilcox is a science writer and blogger who moonlights as a PhD student in Cell and Molecular Biology at the University of Hawaii. Follow on Google+. Follow on Twitter @NerdyChristie.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. all4kindness2all 10:51 pm 07/28/2011

    totally creepy, gross! I am definitely not eating that stuff EVER! ROFL .. fun post.

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  2. 2. zfaulkes 11:09 pm 07/28/2011

    It might not even take salt at all.

    The soy sauce here appears to be poured directly on the skin, and the skin should be acting as a barrier. The frog legs, as far as I can see, have had the skin removed. The salt wouldn’t be coming into contact with the neurons, except maybe the sensory neurons innervating the skin.

    Octopuses, like lots of other invertebrates, have a much more distributed nervous system than vertebrates. It’s estimated that about half the neurons in an octopus are in the arms. The neurons often form circuits contained just within that body part that can generate coordinated patterns of movement.

    If this animal was very recently killed, it could very easily be that the neurons are still up and kicking, and just the touch stimulus could be enough to trigger the response.

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  3. 3. ejwillingham 11:19 pm 07/28/2011

    This video reminded me of when we used to “sex” turtles, which required (and still requires) examining internal gonads directly. Even with only the lower half of the turtle, emptied except for a few organs, the legs would still kick around so much that sometimes, they’d wander offer their ID markers. That could go on for hours.

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  4. 4. foss4us 1:37 am 07/29/2011

    I was wondering about that. Thanks for the informative post; I now am far more informed about salt-induced cephalopod zombieism than I ever thought possible.

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  5. 5. lmelahn 10:13 am 07/29/2011

    Respectfully, I don’t buy that this squid is dead. As a teaching assistant for intro bio for five years, I supervised many squid dissections. The brain of this squid is very much intact. As for the sodium reaction, it doesn’t explain why the squid is moving his rear tentacles, which were not touched by the soy. If you watch carefully, you can see a tentacle flailing in the back on the left near the very end.
    To me this is an example of terrible cruelty to a sensitive creature with a highly developed nervous system.

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  6. 6. lmelahn 10:16 am 07/29/2011

    I would also like to add that squid live in the ocean, and it’s hard to believe that salt applied to its skin would stimulate such a dramatic reaction. The one thing that has not been mentioned very much is that the soy sauce is apparently hot (which explains why it is in a little teapot). I think what we are really seeing is a pain reaction to boiling soy sauce.

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  7. 7. NerdyChristie 12:48 pm 07/29/2011

    lmelahn: from what I know of cephalopods, a live squid wouldn’t sit still in a nice pretty pose and wait for the soy sauce to be applied.

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  8. 8. Southern Fried Scientist 1:05 pm 07/29/2011

    That critter is most definitely dead.

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  9. 9. lmelahn 5:25 pm 07/29/2011

    I would like to believe he is dead, but am having a hard time with it. I have never handled live cephalopods so I can’t speak to how it should behave. But, the brain is definitely intact. Second, the frog video shows a much different reaction — far slower and more subtle, and that’s with salt applied directly to muscle without a salt-impermeable skin barrier. Also, I would like someone to explain how the squid rises up on and flails its rear tentacles, which are untouched by soy sauce.

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  10. 10. Tomsing 7:42 pm 07/29/2011

    lmelahn, I think it’s safe to say that the soy sauce is not boiling hot. The person pouring it holds the small teapot directly – if it were boiling hot, the ceramic would likely be too hot to touch, and they’d hold it by the handle.

    As for the squid rising up on his back tentacles, I’m not sure that’s the case. The side and front tentacles extending is what causes the squid to rear back. If the rear tentacles were stiffening, the squid would tilt forward.

    As for the different reaction of the frog, my guess is that it’s attributable to the different structure – primarily, frog legs are bones and skeletal muscle. Squid have … well, I guess I don’t know my invertebrate anatomy that well. But they’re not bones and skeletal muscle.

    I do wonder about the effect going through the skin, though.

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  11. 11. lmelahn 8:31 pm 07/29/2011

    Tomsing, thanks for your comments. I think you are right about the temperature of the soy sauce, and I think the different movement could be explained by the bone anatomy. The skin barrier bothers me, as well as the instantaneous, dramatic, coordinated reaction. Even if the squid isn’t rising on the rear tentacles, there is one rear tentacle on the left side that very clearly moves at the end of the clip.
    The main thing that bothers me is that the brain is still there. If the animal must be very freshly dead in order for the reaction to occur, and the brain is intact, I am not sure how the animal can be confirmed dead, in the absence of a squid coroner checking for brain activity.

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  12. 12. GAry 7 11:58 am 07/30/2011

    Ok, that’s just creepy.

    I’ll never have anything on my plate that’s still moving.

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  13. 13. neuromusic 1:47 pm 08/1/2011

    Couldn’t the MSG in the soy sauce be activating glutamate receptors?

    (Is glutamate excitatory in cephalopods?)

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  14. 14. ChasCPeterson 4:55 pm 08/2/2011

    There’s no need to invoke neurons, not for the froglegs anyway. Vertebrate skeletal muscle is itself excitable, the membranes including the same voltage-gated ion channels that cause action potentials in neurons. The huge concentration gradient for sodium is very likely depolarizing the muscle cells directly.

    As for the squid, uh, things aren’t so clear, as has been discussed at Pharyngula and Jerry Coyne’s blog, and probably others. That’s just the squids decapitated head, and there’s a good possibility it ain’t ‘dead’ yet.

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  15. 15. ChasCPeterson 4:57 pm 08/2/2011

    and yes, glutamate is excitatory for cephalopod neuromuscular junctions.

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  16. 16. quixote218 11:04 pm 08/7/2011

    lmelahn,

    The brain is most certainly NOT there in the video above. But rather than quibble about the location of the squid’s brain (which I know nothing about), I will refer you to this video: http://www.youtube.com/watch?v=kDYr1rt4XYU There you not only see the preparation of this dish (cutting the brain to pieces, it seems), but also you can see the effect on individual tentacles that have been cut from the body. I don’t have an explanation for the permeability of the skin, as you point out, but it doesn’t really matter what we think since we can see the effect directly.

    Also, ZOMBIES. :)

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  17. 17. lmelahn 2:56 pm 08/19/2011

    quixote218, I watched your video link (which, by the way, is entitled HOW TO EAT LIVE SQUID). The brain was definitely, positively not removed. not even close.

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  18. 18. lmelahn 2:59 pm 08/19/2011

    What you see getting cut into pieces in the video is the squid’s viscera. The brain is located around the squid’s mouth, below the eyes, near the base of the tentacles.

    Link to this

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