ELECTRIC EELS CAN DELIVER A POWERFUL PUNCH

by Whit Gibbons

July 24 , 2016

I recently read a scientific paper by Kenneth C. Catania (Vanderbilt University) that jolted my memory back to a 2-second time period I had not thought of in decades. I was behind the scenes in the Fort Worth Zoo with a friend and the zoo's director, who said, "Go ahead and see if you can pick it up, but it's pretty slippery."

I took the challenge, because I was young and was pretty sure a foot-long eel couldn't be that hard to hold on to. I reached into the small aquarium, putting one hand in front of the snout of the dark gray animal with the yellow belly as it swam away and then lifting it up from below.

That's when I got the shock of my life. I had just grabbed an electric eel to the amusement of my audience of two. A little zoo and aquarium humor at play.

Electric eels may sound like a comic book fantasy but they belong to the knifefishes that inhabit the American tropics. Knifefishes have special organs that build up electrical potential and produce currents used as a means of communication the way birds use sound. In essence they talk to each other.

A knifefish can distinguish between its own species and others and can even determine the sex of another individual of its own kind by the electric waveform generated.

Some species are capable of using their electric receptors to discriminate between individuals of their own species by the fine details of the electrical signature, which varies subtly from one individual to another in a manner perceptible to another knifefish.

The electric eel is the superhero among the knifefishes with their already impressive super powers. Most knifefishes can generate no more than a few millivolts of electricity. But the electric eel, with its thoroughly appropriate scientific name, Electrophorus electricus, can knock your socks off by delivering more than 600 volts! When an electric eel talks, everybody listens.

An electric eel can deliver a discharge directly by touching a victim, whether it be a prey animal being subdued, a would-be predator or some other threat. Although powerful, the shock would not likely be lethal to a healthy adult human. But the bigger the eel the stronger the potential impact. The one I grabbed as a kid was small and delivered a shock well below that of standard 120-volt house current. But electric eels can reach more than 6 feet in length, and when large ones attack, they can stun a full-grown horse.

In fact, an encounter between horses and electric eels was addressed by Catania in his well-designed research study published in the Proceedings of the National Academy of Sciences.

Although his research was focused on electric eel "predatory behavior and sensory abilities," he resolved a two-centuries-old conundrum about whether a story told by Alexander von Humboldt, an early naturalist, was true. The explorer had related a story of horses being used in 1800 in an unusual fashion to capture large electric eels in the floodplain of the Orinoco River.

As Catania explained it, horses were herded "into a pool containing electric eels, provoking the eels to attack by pressing themselves against the horses while discharging."

When the eels had exhausted their electrical charges, they "could be safely collected." Understandably, many scientists have considered von Humboldt's story to be an exaggerated account about eels having the capability to jump up out of the water and shock a perceived threat.

Catania offers convincing evidence that the story has credence. He found that when threatened by a much larger animal, an electric eel will attack, launching itself from the water and using its chin to discharge "high-voltage volleys." The effort leaves them temporarily unable to deliver another charge.

Considering von Humboldt's account of how horses fell down after being stunned by the electric charges delivered by the big eels, I'm glad the one I grabbed was a little tyke.

If you have an environmental question or comment, email

(Back to Ecoviews)

 

 
SREL HomeUGA Home SREL Home UGA Home