September 15, 2017
Researcher puts his own body on the line to test eel’s shock power
For the first time, a scientist has found concrete evidence supporting a old tale by famed German naturalist Alexander von Humboldt in which he described electric eels leaping up from the water to attack horses – and the author of the new study put his own body on the line to do so.
That brave (or foolish, depending upon your perspective) man was Ken Catania, a neurobiologist at Vanderbilt University who reached into a tank containing a small electric eel 10 times in order to obtain accurate measurements of the circuit connecting created by eel, body part and water.As the university said in a statement, the measurements allowed Catania “to solve an equation he can extrapolate to measure the power released by bigger eels,” some of which can be up to 8 feet in size or longer. His findings also support von Humboldt’s story, the New York Times added.
As Catania explained in a previous study, von Humboldt purportedly observed electric eels leap from the water to attack horses, pressing themselves against the horses’ legs while zapping them. Once the eels had exhausted their current, they could be safely collected, he said. While this tale has persisted, the behavior had not been seen again by scientists for more than two centuries.
In 2016, Catania reported finding “a defensive eel behavior that supports Humboldt’s account.” He saw an eel leap from the water and press its chin against an apparent threat while discharging high-voltage energy – behavior that would allow the eel to defend itself during the Amazon dry season, he explained in the Proceedings of the Natural Academy of Sciences (PNAS).
Large eels ‘more powerful’ than ‘a law enforcement Taser’
Now, as NPR reported on Thursday, the Vanderbilt neurobiologist has taken his research to the next level – measuring the electric potential of these eel as part of an August study and allowing the creatures to actually shock his arm in order to see what their discharge actually feels like.
In the journal Current Biology, Catania revealed that the small eel delivered a current that peaked at about 40 to 50 milliamps, but his calculations indicate that a larger one would pack far more of a punch. Such a shock, he told NPR, would be “much more powerful... and [come] at a pulse rate that is higher than the pulse rate given off by a law enforcement Taser.”
Based on his current and previous work, Catania found that eels use this ability to capture prey or to protect itself from perceived threats. They disable or paralyze their prey by delivering current through the water, and wrap around larger creatures in order to shock them directly by forming a circuit. He first observed this behavior while trying to remove them with a metal-handled net.
“Electric eels, in my experience, had never done something like that where they come out of the water, and they did it in a very directed way,” he explained to NPR, adding that he heard their electrical output over a speaker. “I knew that when they were attacking the net in this way, they were simultaneously giving off a high voltage discharge. That clue led me to think, ‘Well, maybe this is sort of a defensive behavior.’”
Study finds that eels can remotely control victims’ nervous system
“As the eel came up out of the water, the voltage that I recorded increased in proportion to height. The higher they got, the higher the voltage and that suggested why they might be doing this,” Catania added. So, naturally, he decided to find out what would happen when the eel came into contact with a living animal – specifically, him.
He allowed an eel approximately one foot in size to zap his arm while he held onto a device that would measure the strength of the creature’s current. He told NPR that he was not worried about becoming injured, noting “if you work around electric eels a lot, occasionally you're going to get shocked anyway. so I kind of knew what I was in for.”
The sensation was similar to touching a hot stove or an electric fence, he told the Times, and it even caused him to reflexively withdraw his arm from the water. “The fact that there’s an animal out there that can remotely control your nervous system, I think is a pretty amazing thing.”
While the experience was most likely not the most pleasant one in the world, Catania told NPR that the research was informative. “It does allow us now to think about and make some pretty reasonable estimates about, ‘Given an eel of size X and water resistance of a known resistance, how much power would one of these eels be able to divert to a human being that was standing in the water?’”
Image credit: Vanderbilt University