Electric eels are among the most badarse predators on planet Earth. How many other creatures can deliver a shock powerful enough to paralyse a horse? But their superpowers are even more impressive than we realised. These eels don't just use electricity to attack, they use it to see.
That's the conclusion of a fascinating study published today in Nature Communications. In a series of laboratory experiments, neurobiologist Ken Catania and colleagues show how electric eels "electrolocate" their prey after paralyzing it, using energy fields to locate and swallow hapless victims almost instantly.
"The eel can use its electric attack simultaneously as a weapon and a sensory system," Catania told National Geographic. "It's sort of a science-fiction-like ability."
Electric eels, which are actually a type of catfish, slink quietly about in the murky depths of the Amazon River, looking for ill-fated creatures on which to discharge their 600-volt weapon. We've known of the eel's formidable hunting ability for decades, but the exact mechanics have proven difficult to study (you try capturing an 8 foot-long living taser and bringing it back to the lab — it ain't easy).
Catania is more persistent than most. In a study published last year in Science, he showed that electric eels' high voltage attacks can stimulate their prey's motor neurons, causing involuntary muscle twitching. Using two or three small electric volleys, the eels will force prey to give away their location before charging up and delivering the paralyzing blow.
Electric eel honing in on an electrically conductive stimulus (red arrow), before initiating its suction-feeding strike. Image Credit: Catania et al. 2015
But how does the eel find its lunch once that prey is disabled? As Catania points out, electric eels will strike and engulf their victims lightning fast — usually within milliseconds.
Electricity figures in here, too, according to a series of laboratory experiments performed by Catania and his colleagues. National Geographic explains:
To understand what was happening, Catania brought electric eels into the lab and presented them with anesthetized fish that were insulated from the eel's electroreceptors by plastic bags. With an electrode, Catania made the fish flinch, and the eel discharged its high-voltage attack. But then it didn't seem to know what to do next — the eel lunged in the direction of movement in the water but didn't attempt to suck the fish into its mouth.
Catania then put an electrically conductive carbon rod into the tank along with the fish. He made the fish flinch, and the eel attacked with a shock. Sometimes the eel started to move in the direction of the fish, but then it changed course to lunge at the rod wherever it had been placed in the tank. To the eel, the fish seemed to be in two places at once.
What these experiments are showing is that electric eels don't just use voltage to immobilize prey: They follow electric fields, in order to track it. This places the eel in league with sharks, rays, and certain African fish as a predator that can electrolocate — an adaptation that's similar to echolocation in bats and dolphins.
Me, I'm just grateful this particular hunting ability seems restricted to the water.