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There are at least three species of electric eels (Electrophorus spp.), not just as previously thought. Two new species have recently been described with the support of FAPESP by a group of researchers affiliated with the Smithsonian Institution and the National Geographic Society, among other institutions. One of the new species can discharge up to 860 volts, the most powerful of all known animals.

The electric eel is a naked hair knife (Gymnotidae) and are more closely related to catfish and carp than to other eel families.

The study, published in Nature Communications, not only provides new knowledge about the animal more than 250 years after its initial description, but also opens up new avenues for research on the origin and production of powerful electric shocks in other species of fish.

Gymnotiformes, the family of the knife-fish to which Gymnotidae belong, are native to Mexico and South America, are found almost exclusively in freshwater habitats, and are mostly nocturnal. There are currently about 250 gymnotiform species valid among 34 genera and five families.

All are capable of producing a weak electric field for communication and navigation (most have very small eyes).

"The electric eel, which can reach 2.5 meters long, is the only fish to produce such a discharge, it uses three electrical organs.The shock is used for defense and predation purposes," said Carlos David de Santana, associate researcher at the National Museum of Natural History of the United States (NMNH), administered by the Smithsonian Institution, and first author of the article.

By correlating DNA, morphology and environmental data and measuring the discharged voltage, the researchers concluded that the animals in question should be reclassified into three species. The only species of electric eel known to science was Electrophorus electricus, described by the Swedish naturalist Carl Linnaeus in 1766.

<div data-thumb = "https://scx1.b-cdn.net/csz/news/tmb/2019/2-smithsonians.jpg" data-src = "https://scx2.b-cdn.net/ gfx / news / hires / 2019/2-smithsonians.jpg "data-sub-html =" The rivers of South America are home to at least three different species of electric eels, including a newly identified species capable of to generate a larger electric shock other known animal, according to a new analysis published in the September 10, 2019 issue of the journal Nature Communications. Electrophorus voltai (above), one of two recently discovered species of electric eel, lives primarily further south than Electrophorus electricus on the Brazilian shield, another mountainous region. Scientists have discovered that E. voltai can discharge up to 860 volts of electricity – far more than the previously known 650 volts generated by E. electricus. This makes the species the most powerful bioelectric generator known and can be an adaptation to the lower conductivity of mountain waters. Credit: L. Sousa ">

<img src = "https://scx1.b-cdn.net/csz/news/800/2019/2-smithsonians.jpg" alt = "The Smithsonian scientists triple the number of species in the world. known electric eels” title=”The rivers of South America harbor at least three different species of electric eels, including a newly identified species capable of generating a greater electric shock than any other known animal, according to a new analysis published in the newspaper of September 10, 2019 Nature Communications. Electrophorus voltai (above), one of two recently discovered species of electric eel, lives primarily further south than Electrophorus electricus on the Brazilian shield, another mountainous region. Scientists have discovered that E. voltai can discharge up to 860 volts of electricity – far more than the previously known 650 volts generated by E. electricus. This makes the species the most powerful bioelectric generator known and can be an adaptation to the lower conductivity of mountain waters. Credit: L. Sousa”/>

In addition to E. electricus, the researchers have now found enough differences to add two new species to the genus: E. varii and E. voltai.

The authors of the article also include Luiz Antonio Wanderley Peixoto, currently at MZ-USP for a postdoctoral fellowship under the supervision of Aléssio Datovo da Silva, senior researcher for the thematic project.

"We have used voltage as a key differentiating criterion, which has never been done before to identify a new species," said Menezes. During field measurements using a voltmeter, the researchers recorded a discharge of 860 volts, the highest of all animals, for a specimen of E. voltai. The strongest shock recorded previously was 650 volts.

The name of the species pays tribute to the Italian physicist Alessandro Volta, who invented the electric battery in 1799, based on the electric eel.

E. varii Richard P. Vari, a Smithsonian researcher, died in 2016. He is the foreign researcher who has most influenced and helped Brazilian students and researchers in the study of fish in South America, Santana said.

A shocking diversity

According to Santana, who has penetrated many rivers to collect electric eels for research purposes and has been electrocuted more than once, the discharge is high voltage but low amperage (about 1 ampere); it is not necessarily dangerous for humans.

For comparison, a shock caused by an outlet can reach 10 or 20 amperes. If you are unfortunate enough to receive one, you may be unable to pull your finger, in which case it can be fatal.

<div data-thumb = "https://scx1.b-cdn.net/csz/news/tmb/2019/1-smithsonians.jpg" data-src = "https://scx2.b-cdn.net/ gfx / news / hires / 2019/1-smithsonians.jpg "data-sub-html =" The rivers of South America are home to at least three different eel species, including a newly identified species capable of to generate a larger electric shock other known animal, according to a new analysis published in the September 10 issue of the newspaper Nature Communications. One of two recently discovered electric eel species, Electrophorus varii (above), bears the name of the late Smithsonian ichthyologist Richard Vari and swims in the murky waters of the slowly flowing plain. Credit: D. Bastos ">

<img src = "https://scx1.b-cdn.net/csz/news/800/2019/1-smithsonians.jpg" alt = "Smithsonian scientists triple the number of species in the world. known electric eels” title=”The rivers of South America harbor at least three different species of electric eels, including a newly identified species capable of generating a greater electric shock than any other known animal, according to a new analysis published in the issue September 10th of the newspaper Nature Communications. One of two recently discovered electric eel species, Electrophorus varii (above), bears the name of the late Smithsonian ichthyologist Richard Vari and swims in the murky waters of the slowly flowing plain. Credit: D. Bastos”/>

The electric eel, however, does not emit a direct current, but an alternating current (in pulses), and its charge is exhausted after a violent shock. His electric organ takes a long time to recharge. Even in this case, meeting with a group of these animals in the water can be very dangerous. The shock will not kill a healthy person, but it can be dangerous if your heart is weakened. It can also contribute to a fall or drowning.

"The shock stuns the victim and is powerful enough to help the fish capture prey or scare away a predator," Santana said.

Research conducted by the group showed that electric eels communicated to gather groups that could electrocute a potential threat. Contrary to what has been claimed in the scientific literature, these animals are not solitary and often associate in groups of ten at most in adulthood.

The new classification was based on an analysis of 107 specimens collected from different parts of the Amazon in Brazil, Suriname, Guyana and Guyana. Initially, researchers used DNA barcoding to sequence the mitochondrial cytochrome c oxidase I (COI) gene, the de facto standard for DNA barcoding in animals. They then sequenced nine other mitochondrial and nuclear genes and performed several other analyzes to validate the results of the DNA barcode.

"Their body shape is very conserved, it has not changed much in 10 million years of evolution, only a few details of their external morphology distinguish them, and only an integrated analysis of morphology, of genetics and ecology made it possible to make solid species distinctions, "Santana explained.

Ecological separation

In addition to showing clear genetic differences, the sequencing data were cross-referenced with ecological data. The species that kept the name E. electricus This Georgian is limited to the north of the Amazon by the Guiana Shield, which encompasses the northern regions of three Brazilian states (Amapá, Amazonas and Roraima), as well as Guyana, French Guiana and Suriname.

E. voltai lives the Brazilian Shield, which encompasses the south of Pará and Amazonas, as well as the Rondônia and the north of Mato Grosso. The shield regions are relatively high, exceeding 300 meters of altitude. It has rapids and falls, with clear, well-oxygenated water, rocky or sandy bottoms and low amounts of dissolved salts. These features favor both species, which have a flat head that helps them to swim gently and hunt in fast-flowing waters on stony river beds.

The small amount of dissolved salts makes the water less conducive to electricity. Researchers believe that animals must produce more powerful rejects to capture their prey. This is especially the case for E. voltai, which has proven to produce the highest blood pressure ever recorded in an animal.

On the other hand, E. varii lives in the lower part of the Amazon Basin and lives in troubled rivers, with relatively little oxygen and sandy or muddy bottoms. In addition, a relatively large amount of dissolved salts increases the conductivity of the water, thus promoting the propagation of their electrical discharges, which vary in this species from 151 to 572 volts.

The researchers believe that the species have diverged twice. The first time, it was in the Miocene, about 7.1 million years ago, when they separated from their common ancestor. It was only until the Pliocene, about 3.6 million years ago, that E. voltai and E. electricus reached their current status.

The researchers plan to conduct further genetic studies to test the hypothesis that ecological separation (protected environment from the floodplain) was one of the factors that led to E. varii (floodplain) and E. electricus and E. voltai (shield) to diverge from their common ancestor. In addition, they continue to capture samples to measure releases and confirm the record of 860 volts. They expect to find new species among the other kinds of electric knife fish.

"The discovery of new species of electric eels in the Amazon, one of the biodiversity hotspots of the planet, is indicative of the large number of species that remain to be discovered in the In addition, the region is of great interest for other scientific fields, such as medicine and biotechnology, reinforcing the need to protect and conserve it, and is important for studies involving partnerships between Brazilian researchers, and between us and groups from other countries, to explore the biodiversity of the region, "Santana said.

Other groups are currently studying the possibility of using the results of electrical eel research to analyze the enzymes produced by their electrical organs in order to determine their applicability as drugs for neurodegenerative disorders such as as Alzheimer's disease or as a model for developing prosthesis batteries and implanted sensors. in the man.