A previously undiscovered species of electric eel which delivers a shock with more than three times the voltage of a domestic plug socket has been discovered in the Amazon rainforest.
The enormous 2.5 metre eel has been named the Electrophorus voltai after Alessandro Volta, the Italian physicist who invented the battery.
The animal, a type of knifefish, can discharge an electric shock reaching as high as 860 volts, the most powerful of any animal known to science.
The research by a team from the São Paulo Research Foundation, comprising scientists from the Smithsonian Institute and National Geographic Society, also revealed a further distinct species of electric eel ? bringing the planet's recognised electric eel species up from one, to three.
"It's quite literally shocking, when you discover new diversity in such an eye-catching fish first described 250 years ago," lead author of the research paper, Carlos David de Santana, from the US National Museum of Natural History told the New York Times.
The enormous voltage from the new species was one aspect of how the team split what was previously recognised as one species, into three separate species.
The use of the voltage an animal can produce is a first in taxonomy.
The team also correlated DNA, morphology and environmental data to conclude the animals in question should be reclassified into three species.
The only species of electric eel previously known to science was Electrophorus electricus, which Swedish naturalist Carl Linnaeus described in 1766.
In addition to E. electricus, now defined as the species living in the northernmost part of the Amazon region, the researchers found sufficient differences to add two new species to the genus: E. varii and E. voltai.
Professor Naércio Menezes, of the University of Sao Paulo's Zoology Museum, said: "We used voltage as the key differentiation criterion. This has never been done before to identify a new species."
During field measurements using a voltmeter, the researchers recorded a discharge of 860 volts, the highest found in any animal, for a specimen of E. voltai. The strongest shock previously recorded was 650 volts.
While the voltage is high, the team said due to the low amperage of the shocks, they are unlikely to be lethal to humans.
In the traditional analogy for understanding measurements of electricity, instead of an electrical wire, imagine a hose pipe. The water is the electricity, and the voltage is the water pressure ? set at a certain level whether the tap is on or off. The amperage is the rate at which water flows down the hose pipe when the tap is switched on ? this is also governed by the resistance, measured in ohms ? the level of which is equivalent to the size of the hose pipe
According to Dr Santana, who has entered many rivers to collect electric eels for research purposes and been shocked more than once, the discharge is high voltage but low amperage (approximately 1 amp), so it is not necessarily dangerous to humans.
As a comparison, a shock from a power outlet can be 10 or 20 amps.
Nonetheless, a shock from the world's most powerful electric eel would not be a pleasant experience.
"I remember the first time I was shocked," Dr de Santana told the New York Times. "I was scared," he said, adding he had dropped his equipment.
The research team also learned more about the social characteristics of the animals. Electric eels had previously been thought of as solitary creatures, stalking prey on their own under cover of darkness.
They reported that the eels had been observed working together to coordinate their predatory manoeuvres, almost like lions on a hunt, but lions armed with electricity.
"This social behaviour is quite unusual," Professor Menzes said. "They come together in a school, surround the fish they feed on, release electricity and kill it."
The research is published in Nature Communications