Along the murky bottom of the Amazon River, serpentine fish called electric eels scour the gloom for unwary frogs or other small prey. When one swims by, the fish unleash two 600-volt pulses of electricity to stun or kill it. This high-voltage hunting tactic is distinctive, but a handful of other fish species also use electricity: They generate and sense weaker voltages when navigating through muddy, slow-moving waters and when communicating with others of their species through gentle shocks akin to morse code.
Normally, when several species share an ability as unusual as generating electricity, it’s because they’re closely related. But the electric fish in the rivers of South America and Africa span six distinct taxonomic groups, and there are three other marine lineages of electric fish beyond them. Even Charles Darwin mused on both the novelty of their electrical abilities and the strange taxonomic and geographic distribution of them in On the Origin of Species, writing, “It is impossible to conceive by what steps these wondrous organs have been produced” — not just once, but repeatedly.
A recent paper published in Science Advances helps to unravel this evolutionary mystery. “We’re really just following up on Darwin, as most biologists do,” said Harold Zakon, an integrative biologist at the University of Texas, Austin and co-senior author of the study. By piecing together genomic clues, his team in Texas and colleagues at Michigan State University uncovered how a number of strikingly similar electric organs arose in electric fish lineages separated by roughly 120 million years of evolution and 1,600 miles of ocean. As it turns out, there’s more than one way to evolve an electric organ, but nature does have some favorite tricks to fall back on. [Continue reading…]