A recent experiment about a leaping eel has confirmed a 19th century myth on how the snake-like fish stuns and attacks land predators.
A naturalist named Alexander von Humboldt told a story about his experience in the Amazon, where he saw a startling fight between horses and electric eels. However, after two centuries, no scientific evidence emerged to support such behavior of the animals. With this, the story of von Humboldt was subsequently referred to as exaggerated.
"The first time I read von Humboldt's tale, I thought it was completely bizarre," says study author Kenneth Catania from Vanderbilt University. "Why would the eels attack the horses instead of swimming away?"
In 2015, Catania accidentally found that under some circumstances, the electric eels that he has been observing sometimes react more significantly than what van Humboldt depicted.
The particular observation he had was that when the animals are blocked by a threatening material that is just partially submerged in water, they will attack by lifting themselves out of the water and straining their chin on the material's side, sending a series of strong electrical shocks.
A Serendipitous Yet Highly Valuable Discovery
Catania then continued to keep the eels in big tanks. At first, he used a net with a metal rim and handle to scoop the animals. Although it was not that convenient, it led him to a valuable idea. When he was picking up the larger eels, he noticed that they bypassed the net and instead attacked it by jumping out of the water while pushing their chins to the handle. This action could then bring electric shock to a possible threat or predator.
Key Discoveries After The Experiment
Catania found that the animals do not give attention to objects that do not conduct electricity, which is understandable given that living things usually do.
To measure the strength and nature of the electrical impulses that the animals were generating as they leap, he hooked a voltmeter and then an ammeter to an aluminum plate. The readings rose significantly as the eels leaped higher.
When the eels are fully underwater, the power of the shock is distributed across the water. As the eel gets out of the water, the electrical pulses go to its chin and directly to the material. That current then travels through the material until it can be released into the water and back to the eel's tail to complete the circuit.
Catania explains that this mechanism enables the animals to produce maximum-power shocks to land animals that are partially submerged in the water and to send electricity to a bigger portion of the predator's body.
Catania also released another study about electric eels in 2015, where he found that the animals curve their bodies to increase their shock value, showing how, even if the animals are not the largest and scariest predators, they are among the most skilled and powerful.
The recent study was published in the Proceedings of the National Academy of Sciences on June 6.