The electric eel (electrophorus electricus) uses electric shocks reaching 650 volts to hunt for prey, but it appears that this freshwater fish of South America has far more advanced uses for its ability to produce powerful jolts of electricity.
Kenneth Catania, from Vanderbilt University in Nashville, Tennessee, conducted a 9-month study to see how the fish taps on its electrical discharges when hunting for its prey. Through a series of experiments, he found that the apex predator uses its electric pulses as a sort of remote control that it can use to cause its hiding preys to twitch exposing their location. It can also remotely induce involuntary muscle contractions that will immobilize its prey.
For his study published in the journal Science on Dec. 5, Catania placed an eel and a fish with incapacitated brain but intact muscles in the same tank. He observed that the muscles of the fish contracted strongly after the eel discharged electric pulses effectively paralyzing the fish.
Interestingly, the eel did not physically touch its prey. Catania found that the electric shock did not act directly on the muscle of the fish but instead on its neurons that control the muscles. Catania said it is much like how a taser works. Tasers overwhelm the muscle-controlling nerves in the target's body causing the muscles to contract involuntarily.
"Apparently, eels invented the Taser long before humans," Catania said. "They can generate hundreds of volts - that by itself is incredible. But to use that ability to essentially reach into another animal's nervous system and activate their muscles is a pretty good trick."
Further experiments also revealed one reason why the fish produces quick pairs of low-voltage electric pulses called doublets when searching for prey. It turns out that these doublets, which trigger strong muscle contractions, help the electric eel know the location of hiding preys. The eel attacks once it senses the twitching movements of its prey that were induced by its electrical discharge.
Catania likewise discovered that eels use different types of jolts for different purposes. It uses a different type of electrical shock to find a potential meal and another pulse to paralyze its prey.
"When prey are hidden, eels can emit periodic volleys of two or three discharges that cause massive involuntary twitch, revealing the prey's location and eliciting the full, tetanus-inducing volley," Catania wrote. "Eel high-voltage volleys have been selected to most efficiently induce involuntary muscle contraction in nearby animals."
