Two new species of electric eel have been discovered, which not only triples the number of known electric eels, but one of them has the highest electrical discharge ever recorded in an animal.
For over 200 years, Electrophorus electricus has captured the world’s imagination with its ability to produce an electrical charge, from being the inspiration for the world's first electric battery to the equivalent of Spiderman's spider bite to Marvel villain Electro. However, it’s not given up its secrets easily. It’s not even an eel, instead a type of electric fish closer to a carp or catfish.
Now, a new paper in Nature Communications has revealed more of its secrets, like the fact there is not just one species but three, and one of those can zap with the power of 860 volts (V) – significantly more than the 650 V previously recorded.
Like the estimated 250 other electric fish species living in the Amazon, the eels use their electrical powers to navigate, communicate, and detect objects. However, they are one of the few that also use their current for both hunting and self-defense.
Reaching up to 2.5 meters (8 feet) in length, Electrophorus is found in many of the rivers, streams, swamps, and creeks across the northern parts of South America, and are ubiquitous enough for scientists to have long assumed they were a single species.
As part of a wider collaboration between the Smithsonian, the University of São Paulo’s Museum of Zoology, and other research institutions exploring the diversity of electric fish in South America, C. David de Santana of the Smithsonian’s Natural History Museum began to suspect there was more to the electric eel than met the eye.
De Santana and colleagues closely examined the 107 eel specimens they had collected over the past six years. To begin with, they couldn’t find any distinguishable outward features that might mark them as different groups. However, when they turned to their DNA, they found genetic differences that clearly pointed to three distinct species.
Upon reexamining the animals, they discovered subtle physical differences, like skull shape and pectoral fin characteristics. Each species also appeared to be confined to a specific region.
The long-known E. electricus is found in the highlands of the Guiana Shield, along the border of Venezuela and Guyana. E. voltai, one of the two new species, lives slightly further south in the highlands of the Brazilian Shield, and E. varii is found in the slow-moving, murky waters of the lowlands.
They suspect the three species split around 7 million years ago, with the common ancestor of E. electrus and E. voltai enjoying the clear waters of higher up, and E. varri heading for the more conductive, mineral-rich waters of the lowlands. E. electrus and E.voltai diverged from their common ancestor around 3.6 million years ago, when the Amazon river changed its course, splitting the highlands.
Curiously, De Santana and team also discovered E. voltai can discharge up to 850 volts of electricity, compared to E. electricus’s 650 volts, making it the “strongest living bioelectricity generator” ever recorded. It's not entirely clear why one species would develop a much higher charge than the other when they both live in the low-conductivity highlands of Greater Amazonia.
"One can speculate that it could be a physiological adaptation to live in environments with low conductivity (as in the highlands)," Dr de Santana told IFLScience. "However, E. electricus lives in a similar environment and does not produce such strong discharge."
Luckily, de Santana confirms none of the species are currently threatened, but describes the current situation in the Amazon rainforest as "heartbreaking", and that we should keep in mind that we have only reached the tip of the iceberg (between 1-10 percent) when it comes to discovering, and understanding, the biodiversity of the Amazon.
"When burning down Earth’s hotspots of biodiversity, like the Amazon Rainforest, it is comparable with burning down a world’s library without knowing 90 percent of the book content," he said.
"Probably what many people (including the Brazilian president) do not realize is that as species become extinct, so too does the health safety of every human. Species are a genetic warehouse that may have a cure for a number of diseases. Compounds initially derived from wild species account for more than half of all commercial medicines."