- Published: 12 March 2009
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Pat Powers, age 11, of New Brunswick, New Jersey, for her question:
How do eels make electricity?
There is no shortage of electricity in the world. In small doses it is present in countless zillions of agitated atoms and molecules. It runs the miniature powerhouse in every living cell. Nerve fibers use it to pulse messages between the brain and body. On a frosty morning it crackles when you brush your hair. The atmosphere has a surplus to squander in dramatic lightning flashes. Electric power is plentiful today because great brains of the past learned to tame and harness a small portion of this giant force.
As a rule, the giant forces of nature are built up from small units. Electricity is one of the smallest particles of the atom. It is freed when numbers of orbiting electrons leave their atoms. Electrons are footloose particles and many factors can tempt them to leave home. They travel their orbits at fantastic speeds and when they depart they take this energy with them. The power of electricity is merely electrons on the move.
Each electron bears a negative electrical charge. An atom with an equal number of electrons and positive protons is electrically neutral. When electrons leave home, atoms try to capture replacements to restore balanced neutrality. The footloose electrons create electricity that whiz to and fro among the atoms.
Electrons may be coaxed to stray by friction, by heat or magnetism. In living tissue they are prodded by the interaction of chemicals. This also happens in a chemical battery. Cells use this electrochemical system to perform a multitude of operations. The electric eel adapts it to run a special powerhouse that sends out electric shocks.
This nine foot snakey fish is related to the catfish and not to the true eels. His powerhouse is located in about 58 inches of fatty tissue at his tail end. Scientists suspect that it is a special adaptation of the nervous system that pulses electric signals between adaptation of the nervous system that pulses electric signals between brain and body. Originally, perhaps its cells were intended to become long muscle fibers. Instead, they became stubby little electroplaxes that act much like flashlight batteries. Nerve impulses trigger normal muscle fibers to contract. In the electric eel, they trigger the electroplaxes to send the current from cell to cell. When trillions of them release their electric charges together, they send out a jolt strong enough to stun a human swimmer.
The electric eel lurks in muddy tributaries of the Amazon and other murky waters of South America. He uses one section of his electric organ to send out a continuous series of fast, weak signals. The impulses bounce back from fish, stones and other solid objects in his watery world. He catches and interpretes them with the help of two sensitive pits in his head. When danger lurks, he uses his batteries to release a stunning, death dealing jolt.