Scientists have long assumed there was only one species of electric eel. (After all, who needs more?) But when a team of researchers examined more than 100 electric eels from South America’s Amazon Basin, it found that there are actually three species—one of which delivers the strongest shock ever measured in a living animal.
To come up with a definitive family tree, researchers looked at 107 eels captured in Brazil, Suriname, French Guiana, and Guyana. They analyzed the eel DNA, examined their body and bone structures, and mapped where they were caught. The data revealed three genetically separate groups with distinct geographical ranges, the researchers report today in Nature Communications. Electrophorus electricus lives the farthest to the north, mostly in Guyana and Suriname; E. varii is spread along the lowland Amazon Basin, mostly in northern Brazil; and E. voltai’s range dips even farther south into Brazil.
Although the species are nearly impossible to distinguish by sight— they all have brown wrinkly skin and frowny mouths—the team was able to find subtle differences in skull shape and body structure. E. electricus and E. voltai, for example, have depressed skulls that may have evolved as an adaptation for finding food on rocky river bottoms, or for efficient swimming in fast-flowing currents.
The scientists also placed the eels in inflatable swimming pools to measure the strength of their shocks. They found that one of the new species, E. voltai—named after Alessandro Volta, the inventor of the battery—can deliver a shock of 860 volts, well above the previous maximum zap of 650 volts. For context, sticking a fork in a socket would rattle your body with anywhere from 120 to 240 volts, and a taser can deliver about 1200.
The eels may have diverged from each other after being separated by the development of a major Amazon floodplain more than 3 million years ago, the researchers say. They did not test whether the different eel species would be able to interbreed if given the chance, but after millions of years of divergent evolution, it isn’t likely that sparks would fly.