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Electric eels curl up to deliver stronger shocks to their prey, which shows that they instinctively apply the laws of physics to their advantage.
The discovery, published on October 29 in the journal Current Biology, was made by Kenneth Catania, professor of biological sciences at Vanderbilt University, in Nashville, Tennessee.
The researcher has devoted 3 years of his life to analyzing the electric fields employed by this fish species, found in the fresh waters of the Orinoco and Amazon River basins in South America.
Electric eels, which can grow up to weigh more than 44 pounds and to measure more than 8 feet, mostly feed on invertebrates, although some adult species may consume fish and smaller mammals.
In order to attack prey, these aquatic creatures generate electric shocks, using 3 pairs of abdominal organs that produce low voltage and high voltage electricity.
The organs account for around two-thirds of the eel’s body, and contain thousands of specialized disk-like cells called electrocytes. These are lined and stacked together, similarly to an electrical battery, and each of them corresponds to an electric potential difference of 0.15 Volts.
When a prey is identified, the eel’s brain sends signals to these electrolytes, and as sodium ions are pumped through, the polarity is reversed.
Electric current is generated as the cells discharge in unison, and this shock can reach up to 600 volts and 1 ampere, for a matter of 2 milliseconds. This reaches the victim’s motor nerves, causing powerful muscle spasms and temporary paralysis, leaving the prey completely defenseless.
While this shock isn’t normally deadly for a human adult, because of its reduced duration, it’s still similar to being zapped by a Taser gun, and 5 times stronger than the voltage of a wall socket.
Researchers have now discovered that in fact electric eels have the ability to make this lethal weapon even more potent, by manipulating electric fields and doubling the amount of electric shock they deliver.
This suggests that they are in fact much more complex creatures, which can adapt their attack even to larger and more elusive prey.
Overall, electric eels use low-voltage discharges to swim through their environment, short bursts of high-voltage current while seeking prey, and stronger pulses of higher frequency and voltage during attack and defense.
When it comes to hunting larger species such as crayfish, the eels initially bite, and then wrap their tail around the quarry, thus bringing their negative pole closer to the positive pole located in the head.
Only after they’ve curled up this way do they release electric pulses, and according to experiments conducted by placing electrodes in fish treats, those shocks are twice as potent as regular ones, resulting in severe muscle fatigue and incapacitation.
“The prey animals are completely paralyzed. The effect is comparable to administering a dose of paralytic agent like curare”, explained Catania.
The researcher also discovered that during hunting electric eels emit 2 or 3 millisecond high voltage discharges, known as doublets or triplets. Those cause fish hiding nearby to twitch, disturbing the water and revealing their location. This allows eels to compensate for their poor vision, and easily identify prey.
Therefore, electric fields function not just as a weapon against quarry, but also as a complex navigation system, similar to a radar, turning eels into sophisticated and highly effective predators.
Image Source: Flickr
