If there’s any animal that could use a new PR agency, it’s got to be the electric eel. I mean, think about it – what other animal doesn’t even have its own correct name? You’ve probably heard that an electric “eel” is no eel at all but rather a fish (a knifefish, to be exact). From this basic signal that we couldn’t care less, the list of insults continues: for centuries we figured “the” electric eel was a single species. When we finally bothered to check, it turned out there are actually three.
But who cares? Electric eels are just slimy things that will zap you to death, right?
Whatever they’re actually called or whichever species they’re really part of, the one thing everyone can agree on is that electric eels are legendary monsters that kill with their terrifying jolts. Probably thanks to videos like this, in which an electric eel brings a taser to an alligator fight:
The perception also probably has its roots in the famous illustration from the naturalist Alexander von Humboldt’s encounter with eels in South America in 1800: you can see the agonised horses enduring an onslaught of electrical terror.
Electric eels: some of the scariest freshwater animals in the world, but ultimately not so interesting to science.
That wasn’t always the case. For a brief moment, we cared tremendously about the particulars of electric eels. In the 1960s, they were as important to science as mice are today. Back before molecular biology had the sophisticated tools that today help us probe how the body works, it was really hard to figure out how the neuromuscular system worked. How did signals travel between nerves that carried our intention to move our limbs and the muscles that turned intent into action? Electric eels helped us figure out the crucial role of the acetylcholine receptor.
Acetylcholine is basically “giddyup juice” for your muscles. Wherever a nerve meets the muscle it controls, there’s a little gap where the muscle surface is covered in little acetylcholine receptors. The nerve sprays the acetylcholine all over the muscle, and that triggers a cascade of electrical signals that result in your ability to move that part of your body.
Acetylcholine works the same in the eel’s electric organ – a special nerve sprays their electric tissue with it and it discharges a big zap. The reason electric tissue functions just like muscle tissues is because electric tissue evolved from muscle tissue. It was like an evolutionary upgrade. And part of the system update from “standard muscle” to “electric organ” was a massive profusion of these acetylcholine receptors. Every electrocyte (the electrical cell) is absolutely jam-packed with them. They’re a big part of what gives an electric eel its power, and their huge numbers made it easier to study them in eels than in other, non-electrical animals.
But once electric eels were finished helping us figure out the human neuromuscular system, scientists developed more sophisticated ways to poke inside cellular machinery. The field moved on and biologists quickly left electric eels behind.
Well, not all biologists. Not Kenneth Catania, who is probably the world expert in eel behaviour. He’s one of a few scientists still fighting to convince the world that eels still have things to teach us, if only we would listen. The biggest mystery we haven’t yet cracked is how they can generate a shock from inside their body without sending their own hearts into ventricular fibrilliation. Much more bizarrely, we have no idea how the current is transmitted from the electrical organ to the outside of the creature.
A taser, for example, gets electricity from the batteries inside it, out to electrodes by way of wires. The eel? There’s no obvious mechanism. Does it travel through the skin? Between the skin cells? Nobody can tell you.
In his quest to understand more about electric eels, Catania has already made some pretty mind-blowing new discoveries. It was Catania who discovered in 2015 that the way they immobilise their prey is much more interesting than the lazy old assumption that they simply stop the heart. Instead, the electric field they generate around them “instantly fatigues all the prey’s muscles,” he says, like you’ve just done 300 pushups but with your entire body. “Electric eels are like a floating neurotoxin.”
“The shock doesn’t kill you,” Catania says, “but by the time you recover you’ve been eaten by an eel.”
But they don’t just use their shock to freeeze their victims – it’s much more versatile than that. They also use it to locate fish hiding in murky water, a bit like how bats use echolocation. “The electric eel is a battery, Taser, remote control, and tracking device, all in one,” wrote Ed Yong in describing the details of Catania’s research.
This paints a much more interesting picture of electric eels than the simple one most of us may have carelessly inherited. So please join me in cultivating a weird obsession with electric els, and evangelising on behalf of an animal that “has evolved to this degree of almost having superpowers,” as Catania put it to the New York Times in 2014. There are no PR agencies for eels.
Image credits
Eel: Electrophorus electricus. Author: opencage, attribution sharealike license
Video: The internet, 2010
Illustration: Alexander von Humboldt’s story of the battle between horses and electric eels. Credit: Public Domain