Electric eels 'remotely control their prey'
A jolt from an electric eel does more than stun its prey, scientists say.
A study, reported in the journal Science, has now shown that eels can use their electric organs to remotely control the fish they hunt.
A researcher from Vanderbilt University in Nashville, Tennessee, found that the electric discharges from eels made the muscles of their prey twitch.
This makes the fish easier to capture either by immobilising it or making it "jump" to show where it's hiding.
Kenneth Catania, who led the study, set up small aquatic arenas to test the eels' hunting abilities - putting an eel and an unfortunate fish into the same tank.
When they spotted their prey, the eels released pulses of electricity that appeared to immobilise the fish.
Further study revealed that the eels' electric pulses directly activated the nerves that controlled their prey's muscles.
"When the eel's pulses slow down - when the eel gets tired at the end of its attack - you see individual fish twitches, with one twitch from every pulse," said Dr Catania.
"That tells us that the eel is reaching in to the prey's nervous system, controlling its muscles."
In further observations of the eels' hunting strategies, Dr Catania noticed that the hungry creatures would emit pairs of pulses when their potential meal was out of view.
"People had known since 70s that eels give off these pairs of pulses - or doublets - as they explore looking for food," he said.
"Usually when they're excited and they know that food is around but can't find it.
"It actually turns out that this generates very rapid and strong [muscle] contraction."
This essentially makes the fish "jump" and reveal their whereabouts.
"So the eels have an efficient way to induce a massive twitch in their prey.
"You and I couldn't activate every muscle in our bodies at once, but the eels can do that [remotely] in their prey.
"They can completely immobilise prey or they can make prey move, depending on what they would like to do."
Other researchers are studying eels at the molecular level, to find out how they and other electric fish have managed to "build" a battery from muscle tissue.
Dr Catania thinks they are "just fascinating animals in their own right".
"It's amazing in the first place that they can give off electricity," he said.
"To use that to control their prey's nervous system is incredible."