newly discovered electric eel species
© L. Sousa
Electrophorus voltai is one of the two newly discovered electric eel species
An investigation into the diversity of electric eels has produced quite a shock. Rather than just one species, there are actually three species of electric eels living in South America, and one of them generates a bigger voltage than any other bioelectric animal.

Electric eels were first described 250 years ago by Carl Linnaeus, who gave them the species name Electrophorus electricus. They use their shocking power to hunt prey and defend themselves, while weaker electrical signals help them to navigate and communicate.

David de Santana at the Smithsonian Institution, Washington DC, and colleagues studied 107 specimens from across the Amazon region, analysing their genetics, morphology and geographical spread. They discovered that there are three species with different distributions: the original species E. electricus in the northern highlands, E. voltai in the southern highlands and E. varii in the lowland Amazon basin.

E. voltai is the largest, growing up to 1.7 metres long compared with 1.0 metres for the shortest, E. electricus. The researchers measured the electric discharge generated by E. voltai at 860 volts - considerably higher than the 650 volts reported before. This makes it the strongest living bioelectricity generator we know of.

These eels live in water with few dissolved minerals, meaning it has low conductivity, which might be why such a large voltage is necessary. A shock of this size would be unlikely to kill a human, but it would cause muscle contractions and a painful numbing sensation, says de Santana. "It's like the effect of a law enforcement Taser."

E. electricus and E. voltai have a flatter head than E. varii, which may be better adapted to highland environments, with fast-flowing water and rocky or sandy bottoms. The species also differ in the number of pores in their lateral lines - a system of sense organs on the side of the body.

Genetic analysis suggests that the E. varii lineage diverged from the other two species around 7.1 million years ago, with E. electricus and E. voltai splitting around 3.6 million years ago.

Electric eels provided Alessandro Volta with inspiration for the first electric battery in 1800, and more recently inspired a battery that could power medical implants.

If we don't know about the diversity of species alive today, we risk losing knowledge that could be valuable to us, says de Santana. "When a species becomes extinct, so does the health and safety of every human because these species are genetic warehouses that may have a cure for disease," he says.

Journal reference: Nature Communications, DOI: 10.1038/s41467-019-11690-z