Fast Discharge Batteries: Electric Eels

by Emil Morhardt

We write a lot here about electric batteries of various sorts, but one of the oldest ones is the 600 Volt biological battery of the electric eel Electrophorus electricus. These animals search about for hidden prey by emitting a couple of high voltage pulses from time to time to see if anything jumps. If it does, they sidle on over and cut loose a volley of high frequency (~400 Hz) pulses that the muscles of the prey apparently interpret as coming from their own nervous system. The result is many muscles contracting simultaneously, paralyzing the prey into a state of whole-body muscle contraction known as tetanus (similar to the eponymous disease) and the eel sucks them in. This all happens pretty fast, on the order of milliseconds. If the eel fails to suck them in they often just swim away.

In a series of elegant experiments, Kenneth Catania (2014) at Vanderbilt University explored this in some detail by isolating immobilized fish behind an electrically-transparent barrier—keeping the eel at bay—while he measured the eel’s volleys and the prey’s responses. Given that everyone knows electric eels exist, and that electrophysiologists can’t help being interested in them, it is somewhat surprising that all this wasn’t known before. Fisheries biologists know all about the effect of shocking fish because they use electrofishing gear to temporarily stun fish so they can be captured and counted, and I had always assumed it was doing something similar to a hunting electric eel. Dr. Catania and the editors of science interpret this phenomenon in a more nuanced way, characterizing the eels’ behavior as “…remotely control[ling the] muscles of their prey.” Somehow, viewed in that light, the process seems far more nefarious than simply stunning the prey.

Catania, K., 2014. The shocking predatory strike of the electric eel. Science 346, 1231-1234. http://www.sciencemag.org.ccl.idm.oclc.org/content/346/6214/1231

 

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