Scientists Discover How the Shocking Electric Eel Evolved its Jolt to Stun Prey

The electric eel is an unusual creature with the ability to create a potent electric field that it uses to hunt its prey. Now, scientists have uncovered the evolutionary origins of this electric field and have found that the eel's charge actually evolved from a muscle.

The electric organ is an anatomical feature that's found only in fish. Over the course of history, though, this feature evolved independently about half a dozen times in environments ranging from the flooded forests of the Amazon to marine environments. In fact, worldwide there are hundreds of electric fish in six broad lineages. The fact that all of these fish are so widely dispersed and unrelated means that electric fish are a perfect example of convergent evolution.

While the fish may be different, though, their electric organ is somewhat similar. The researchers sequenced and assembled DNA from the electric eel genome and then produced protein sequences from the cells of the electric organs and skeletal muscles of three other electric fish lineages using RNA sequencing and analysis. In the end, they found that electric organs in fish worldwide us the same genetic tools and cellular and developmental pathways to independently create the electric organ.

So how does this "charge" work? All muscle cells have electric potentially. In fact, a simple muscle contraction will release small amounts of voltage. The fish amplified this ability by evolving another type of cell called electrocytes, which are larger cells organized in sequence and capable of generating much higher voltages.

"What is amazing is that the electric organ arose independently six times in the course of evolutionary history," said Lindsay Traeger, one of the researchers, in a news release.

Not only did this organ arise independently, though; the fish also used the same "genetic toolbox" in order to create their electric organ. This organ is usually used by fish in murky environments in order to communicate with mates, navigate, stun prey and defend against other predators.

"I consider 'exotic' organisms such as the electric fish to be one of nature's wonders and an important 'gift' to humanity," said Michael Sussman, one of the researchers, in a news release. "Our study demonstrates nature's creative powers and its parsimony, using the same genetic and developmental tools to invent an adaptive trait time and again in widely disparate environments. By learning how nature does this, we may be able to manipulate the process with muscle in other organisms and, in the near future, perhaps use the tools of synthetic biology to create electrocytes for generating electric power in bionic devices within the human body or for uses we have not thought of yet."

The findings are published in the journal Science.