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Fish like electric eels and torpedoes have specially designed nerve cells that allow them to discharge hundreds of volts of electricity.

Now, while pure water is usually nonconductive, the dissolved salts and other stuff in both sea and fresh water allow them to be conductive. If an electric fish is able to use its electricity to stun enemies or prey, how come the fish itself is unaffected?

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3  
for the same reason snakes don't poison themselves! :D –  Pratik Deoghare Nov 8 '10 at 6:24
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@TheMachineCharmer But a snake would get hurt if bit by itself (or by another of the same species), as long as the venom can act on its tissues. –  Mark C Nov 8 '10 at 7:13
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@Machine: Mark is correct. Snakes do not necessarily have immunity to their own venom; they are merely careful enough not to bite themselves. Their cells are as susceptible to venom proteins as the cells of any other animal. –  user172 Nov 8 '10 at 7:18
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Agreed he is right and you too! The comment wasn't supposed to be taken seriously. :) –  Pratik Deoghare Nov 8 '10 at 9:44
    
@TheM Yes, but I just had to point it out. –  Mark C Nov 10 '10 at 17:51

2 Answers 2

alt text Suppose current entering into this parallel circuit is $10A$
then almost all the current flows through poor small fish's body

current through poor small fish's body = $10A \times \frac{1M}{1M+1} \approx 10A $

This is probably the large picture but I am just guessing. Hope its correct.

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15  
All right, visuals, circuit diagram, freehand fishes, and "poor small fish"! –  Mark C Nov 8 '10 at 7:11
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Are we supposed to understand that the small fish has a lower resistance because it is smaller i.e. it contains less resistive material? And what about the resistance of water? –  Alexandre Jasmin Nov 2 '13 at 0:57
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The picture is awesome. –  Dacto Nov 2 '13 at 4:18
    
@AlexandreJasmin Actually the predator fish can increase his own resistance, see Mark C's answer. –  user144542 Aug 15 at 17:29
    
I'd love to join the upvoters, but I have to point out instead that this doesn't actually answer the question. The question can be translated to "why does the eel have higher resistance". This answer assumes we know the answer to that! –  GreenAsJade Sep 30 at 8:20

I checked to make sure:

The simple answer is that electric eels insulate their critical tissues with a layer of fat below the skin, preventing the shock from traveling through their body as the "path of least resistance". I may update with visuals and details if I can find good ones.

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protected by Qmechanic Nov 2 '13 at 10:36

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