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The Poison Tetrodotoxin


Duality in nature is a peculiar thing.  More often than not, bright beautiful colors are often nature's way of saying "I am poisonous, stay away, do not eat me!".  Most predators know this and keep their distance, giving wide berth to such organisms, save one: The Most Successful Predator on this Planet.  Man.  Even the most successful predator on this planet has its moments.  100-200 of people become ill each year after eating "fugu", or pufferfish each year.  Roughly half of these intoxifications are fatal, even with immediate treatment.(Dr. Chein-Yuan Kao, Brooklyn Medical Center)
Anhydrotetrodotoxin 4-epitetrodotoxin, or Tetrodotoxin, as it is more easily referred to, is 10,000 times more lethal than cyanide.  It is perhaps the most potent toxin present in nature, save two others, which occur in bacteria. (Light,1998)  Tetrodotoxin is present in a other animals besides pufferfish, with the blue-ringed octopus, harlequin frogs, and rough-skinned newts making the list.  Tetrodotoxin has even been isolated from certain strains of algae, along with more marine life such as some snails, crabs and even a type of flatworm.  While tetrodotoxin is not exclusively owned by just pufferfish, our chances of coming into contact with this poison is surely greater with them.
Tetrodotoxin affects the nervous system in such a way as to prevent the propagation of nerve impulses.  While it does not cross the blood-brain barrier, it inhibits the ability of our nerves to send messages to other parts of our body.


Confused?  Here's how it works.  We all use electrical impulses to send messages from our brain to other parts of our body to tell them to do things (yes, I knew you knew that, but I had to start somewhere).  These messages fire from dendrite to axon within the nerve cells, ultimately reaching their destination, in this case a muscle fiber (such as in the heart).  The "messages" involve the passage of sodium (Na+) ions and potassium (K+) ions  across the axon, along the nerve cell membrane.  All you really need to understand is that your nerves need both of these ions to produce the electrical messages (action potentials).  Ultimately, this sends the right message to the muscle fiber shown in the diagram here.  Now, you have these two ions running up and down the cell interacting with only each other and the cell membrane (simply put).  Sodium and potassium are moving in and out of the cell membrane (like the "skin" of the axon) causing changes and carrying the electrical message.  Again, your body needs both of them in order to get the signal across.  Tetrodotoxin binds itself to the sodium ion, preventing it from moving in and out of the membrane.  As you can guess, this pretty much shuts down the entire "message-sending" process, and the impulse never gets to its destination.  Now, knowing that we really need to do this (you said you did earlier, right?) you can imagine what tetrodotoxin would do to us if it got into really vital nerve cells.

Here are some actual nerve cells.  This image was taken from an electron microscope observing stained nerve cells.  A little tetrodotoxin and... well, you get the picture.  Actually, let's describe some of the symptoms of fugu poisoning.  So let's say your sushi chef had a little too much sake the night before and goofed a bit while preparing your meal of pufferfish--
The first signs that something is awry is a slight numbness in the lips and tongue (the sodium ions can't carry the messages, remember?).  This numbness soon increases and spreads to certain parts of your face and throat.  Some reported initial symptoms also included involuntary muscle spasms, weakness, dizziness, and loss of speech.(2001,mednets.org)  There is excessive salivation and sweating, along with slowed heart rate and a drop in body temperature. Victims soon experience respiratory distress, marked by rapid, shallow breathing.  The secondary stage of the poisoning involves increased paralysis, to the point where even sitting becomes difficult.  From this point on it's pretty much downhill.  After another increase in paralysis, mental impairment and convulsions (yes, probably in that order) ensue.  This is followed by an inevitable case of cardiac arrhythmia.  Wait!  It's not over yet.  Do you remember earlier when I mentioned that tetrodotoxin doesn't cross the brain-blood barrier?  This basically means that your brain, although composed of nerve cells, is not directly affected by this toxin.  There have been reports of fugu poisoning survivors that they were completely lucid during the entire event, finally recovering to tell the tale. (M. Lester, 1996)

This may come as no surprise to you voodoo enthusiasts out there (funny to see you guys in the LFS buying shrimp and bloodworms), since your voodoo zombie master (no disrespect, I don't know what else to call you?) uses tetrodotoxin in his zombie powder.  Yes, it's true, this toxin is the main ingredient in zombie making practices in Haiti and West Africa. (Light, 1998)  (If you're a zombie or just want more information, go to google.com and search "Clarvius Narcisse", a zombie case documented by ethnobotonists.)
But I digress--
Death usually occurs within 4 to 6 hours, with a known range of about 20 minutes to 8 hours. If you've survived this ordeal, consider yourself lucky.  Since there is no antidote, medical professionals are left with no alternative but to treat the symptoms.  This is accomplished by removing remaining toxins in your stomach with a charcoal lavage and techniques involving life-support in an artificial respirator.

Let me reiterate, bright colors usually mean "do not eat me".
 


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