Electric eels may be the most "remarkable" predators on Earth because of their unique ability to control their electric fields and take down large prey.
Researchers identified a maneuver that allows the eels to deliver powerful electrical shocks that act as a wireless "Taser," Vanderbilt University reported. The incredible animals can produce: low-voltage pulses to sense their environment; short sequences of high-voltage pulses; and volleys of high-voltage, high-frequency pulses used to capture prey and for defense. The recent experiments revealed the electrical pulses target the nerves in the prey's muscles to cause intense contractions and control it's movement.
"Historically, electric eels have been viewed as unsophisticated, primitive creatures that have a single play in their playbook: shocking their prey to death," said Kenneth Catania, the Stevenson Professor of Biological Sciences at Vanderbilt University. "But it turns out that they can manipulate their electric fields in an intricate fashion that gives them a number of remarkable abilities."
The eel's go-to attack is to bombard its prey with a volley of Taser-like pulses, causing whole-body contractions. If for some reason this does not work or the prey is too large, the eel uses a second form of attack. In this attack the eel bites its prey and curls its tail around it, allowing the eel to deliver stronger electrical pulses to its victim. This behavior had been observed in the past, but had never been explained. The researchers found the curling motion brought the positive pole located in the eel's head closer to the negative pole in its tail, increasing the amount of electrical charge delivered. The increased voltage is so strong it causes intense muscle contractions that lead to fatigue.
"The prey animals are completely paralyzed," Catania said. "The effect is comparable to administering a dose of a paralytic agent like curare."
The eel also uses its electrical "remote control" abilities to emit short sequences of two or three millisecond, high-voltage pulses while hunting to cause body spasms in prey that come near.
"One of the eel's major problems is finding prey in the first place," said Catania. "Their environment in the Amazon is filled with muddy water and all kinds of vegetation that give fish a lot of places to hide. So, as the eel glides along, it emits a doublet or triplet. If there is a fish hiding nearby, then its body will spasm and the spasm will generate pressure waves in the water. Although the electric eels can't see very well, they are very good at detecting water movement. So this reveals the position of its next meal."
The radar is not only good for inducing muscle spasms, the eels can also use feedback from their high-voltage volleys to zero in on the position of their prey.
"This dual use of the high-voltage system as both a weapon and a sensory system indicates that the eels' hunting behavior is far more sophisticated than we have thought," Catania concluded.
The findings were published in a recent edition of the journal Nature Communications.
WATCH:
