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Shocking!

31 Jul

It’s Latin name is torpedo, although the fish doesn’t look much like a missile. It’s small, flat, and quite squat. The immediate image that comes to mind is some sort of aquatic ping-pong paddle. The common torpedo lives in the Mediterranean, where it spends most of its time sitting on the sandy bottom, waiting for prey to wander by.

But this fish is a bombshell, make no mistake. Capable of delivering shocks over 200 volts, the electric ray is a serious predator. It generates this power from two special kidney-shaped organs that lie just behind its eyes, evolutionary derivatives of normal muscle tissue. Normally muscles get their jolt from storing and releasing sodium and potassium ions, cycling through them in regular motions. In electric organs, however, this system has become decoupled. Ions go in, but they don’t go out. The energy is stored, waiting. Each cell carries only a tiny charge, but each organ is made of billions of cells and when they’re all released together the effect is, well, shocking.

People have known about the electric rays power for a long time. Even before we knew what electricity was, the people of the Mediterranean knew that anyone silly enough to try to catch one was in for a numbing, paralyzing spell. In fact, the name torpedo in Latin means “paralyzer”.

And humans, clever little devils that we are, figured out a way to put this power to good use.

From what I can gather, it was a not uncommon practice to use electric rays as a sort of primitive anaesthetic. Before childbirth or surgery, a captured fish would be applied to the target area. The fish, obviously startled and upset, would release its electricity, producing a useful localized numbness.

To be honest, I’ve having some trouble picturing the logistics of this operation, but apparently it was common enough that Scribonius Largus, court physician to the Roman emperor Claudius, recorded it in his Conpositonesan early medical textbook. Older Greek and Egyptian sources are cited as well. Scribonius also recommends using it as a cure for lethargy and headaches.

I can only imagine what a Roman fish market must have looked like.

Sources: MacDonald (1993), Wu (1984), forumromanum.com, burtonreport.com, elasmo-research.org, fish.wa.gov.au

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Posted by on July 31, 2012 in Medicine, Natural History

 

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