Leaping Electric Eels!

Science Daily reports on a not-terrifying-at-all accidental discovery, that electric eels are perfectly capable of jumping out of the water to deliver a lethal dose of electricity when threatened:

In a legendary account the famous 19th century explorer and naturalist Alexander von Humboldt recounted a dramatic battle between horses and electric eels that he witnessed on a field trip to the Amazon. In the following 200 years, however, there have been no scientific reports of similar behavior on the part of the eels, suggesting that perhaps von Humboldt exaggerated.

Last year, Vanderbilt University biologist Kenneth Catania accidentally discovered that, under certain conditions, the electric eels that he has been studying will react even more dramatically than von Humboldt described: When cornered by a threatening object that is partially submerged, they will often attack by raising up out of the water, pressing their chin against the object’s side and administering a series of powerful electrical shocks.

Catania, who is the Stevenson Professor of Biological Sciences, has included a description of this behavior, an assessment of its effectiveness and an explanation of the evolutionary advantages it provides the eels in the paper “Leaping eels electrify threats supporting von Humboldt’s account of a battle with horses,” published online this week in the Proceedings of the National Academy of Sciences early edition.

“The first time I read von Humboldt’s tale, I thought it was completely bizarre,” said Catania. “Why would the eels attack the horses instead of swimming away?”

By hooking a voltmeter and then an ammeter to an aluminum plate, Catania was able to measure the nature and strength of the electric impulses the eels were producing as they leap up the conductor. He found that both the voltage and the amperage produced by the eels increased dramatically as the eel leaped higher on the target.

To visually illustrate this effect, the researcher painstakingly covered a plastic arm and a plastic alligator head with a conductive metal strip and a network of LEDs. When an eel attacks these targets, the electrical pulses it generates cause the LEDs to light up brightly.

“When you see the LEDs light up, think of them as the endings of pain nerves being stimulated. That will give you an idea of how effective these attacks can be,” Catania said.

(In the von Humboldt story, two horses were stunned and drowned in the first five minutes of the skirmish with the eels.)

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