Electric eels leap to deliver painful, Taser-like jolt

September 14, 2017

The electric eel has always been noted for its impressive ability to shock and subdue its prey. It's recently become clear that electric eels also use a clever trick to deliver an intense, Taser-like jolt to potential predators: they leap from the water to target threatening animals, humans included, above water. Now, a researcher reporting in Current Biology on September 14 has measured (and experienced) just how strong that jolt can be.

Those stunning leaps make for a more painful experience because they prevent the eels' electrical discharges from weakening as they dissipate through the water.

"We've known these animals give off a huge amount of electricity, and everybody thought that was really amazing," says Kenneth Catania of Vanderbilt University. "But they aren't just simple animals that go around shocking stuff. They've evolved to produce stronger and stronger electrical discharges, and in concert they've evolved these behaviors to more efficiently use them."

Catania earlier showed that the eels curl their bodies around their prey to double the power of their electrical discharge. In the course of his studies, he noticed something else unusual. If he used an electrically conductive, metal net to scoop up electric eels in his lab, the animals leapt from the water to attack the net.

Catania realized he had accidentally imitated a predatory attack on his eels in shallow water. But, at first, he was "just confused" by their behavior. Why didn't they simply swim away? He soon realized the leaping might help the eels to effectively target a would-be predator and intensify the shock.

In fact, electric eels' leaping behavior had been described by Alexander von Humboldt way back in the 1800s. Humboldt claimed to have witnessed a dramatic battle between electric eels and horses in the Amazon. But, Catania says, "No one really necessarily believed it, or if they did, they thought it was just kind of weird." Whatever they thought, it was more or less forgotten.

To understand the dynamics of the electrical circuit created when an eel contacts another animal, Catania developed an apparatus to accurately measure the strength of the electric current through a human arm when the electric eels leapt in attack. Catania put that apparatus to use with his own arm and a relatively small, and therefore less powerful, eel.

As reported in the new study, the electrical current delivered by the eel peaked at 40-50 milliamps. That's more than enough to cause a person or animal considerable pain, but not enough to actually hurt them. In a video, one can see Catania's arm reflexively pull back, an involuntary reaction similar to what would happen if you touched a hot stove.

"It's impressive that a little eel could deliver that much electricity," Catania says. Of course, they have good reason as they may encounter crocodiles, predatory cats, and "who knows what else," he adds. "We don't know the main driver of the behavior, but they need to deter predators, and I can tell you it's really good at that. I can't imagine an animal that had received this [jolt] sticking around."

Now that he's been able to measure the strength of the electrical current, Catania says he can solve the rest of the circuit. That means it's now possible to estimate the power of a shock delivered by eels of various size or under different circumstances. It turns out the findings are relevant to humans, too. Catania notes that a YouTube video that recently surfaced and went viral shows a fisherman being shocked by a leaping electric eel in the Amazon.

When Catania first saw that footage, it surprised him. But, he now realizes, it's something that's "probably happened a lot." The only difference in the recent case is that someone managed to successfully capture it on video. Now, after voluntarily receiving more shocks in his lab than he cares to recount, Catania has, too.
-end-
This work was supported by the National Science Foundation.

Current Biology, Catania, K.: "Power Transfer to a Human during an Electric Eel's Shocking Leap" http://www.cell.com/current-biology/fulltext/S0960-9822(17)31072-2

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.

Cell Press

Related Behavior Articles from Brightsurf:

Variety in the migratory behavior of blackcaps
The birds have variable migration strategies.

Fishing for a theory of emergent behavior
Researchers at the University of Tsukuba quantified the collective action of small schools of fish using information theory.

How synaptic changes translate to behavior changes
Learning changes behavior by altering many connections between brain cells in a variety of ways all at the same time, according to a study of sea slugs recently published in JNeurosci.

I won't have what he's having: The brain and socially motivated behavior
Monkeys devalue rewards when they anticipate that another monkey will get them instead.

Unlocking animal behavior through motion
Using physics to study different types of animal motion, such as burrowing worms or flying flocks, can reveal how animals behave in different settings.

AI to help monitor behavior
Algorithms based on artificial intelligence do better at supporting educational and clinical decision-making, according to a new study.

Increasing opportunities for sustainable behavior
To mitigate climate change and safeguard ecosystems, we need to make drastic changes in our consumption and transport behaviors.

Predicting a protein's behavior from its appearance
Researchers at EPFL have developed a new way to predict a protein's interactions with other proteins and biomolecules, and its biochemical activity, merely by observing its surface.

Spirituality affects the behavior of mortgagers
According to Olga Miroshnichenko, a Sc.D in Economics, and a Professor at the Department of Economics and Finance, Tyumen State University, morals affect the thinking of mortgage payers and help them avoid past due payments.

Asking if behavior can be changed on climate crisis
One of the more complex problems facing social psychologists today is whether any intervention can move people to change their behavior about climate change and protecting the environment for the sake of future generations.

Read More: Behavior News and Behavior Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.