You’ve heard of electric eels shocking their prey, but did you know they also use their electricity to communicate and recognize other fish? Eels aren’t the only electric fish in the sea. There are several other species of electric fish, and biologists have often wondered about this evolutionary quirk. 

Researchers from the University of Texas in Austin looked to genetics to find out how some fish evolve electric organs. 

Looking closely, the UT Austin team discovered that electricity adaptation had to do with something called the sodium channel gene. All fish have duplicates of this gene, which enables muscles to contract. Electric fish became electric by turning off one of the sodium channel gene duplicates in muscles and keeping it on in other cells. The muscles that would’ve contracted were then made to generate electricity, and the electric organ was born. 

“This is exciting because we can see how a small change in the gene can completely change where it’s expressed,” says Harold Zakon, professor of neuroscience and integrative biology at the University of Texas at Austin and corresponding author of the study in Science Advances

Zakon and his team discovered the small section of the sodium channel gene’s code responsible for turning it on and off. In electric fish, Zakon confirmed, this section of code is either damaged or entirely missing. 

“This control region is in most vertebrates, including humans,” Zakon says. “So, the next step in terms of human health would be to examine this region in databases of human genes to see how much variation there is in normal people and whether some deletions or mutations in this region could lead to a lowered expression of sodium channels, which might result in disease.”

Looking at this specific part of the genetic code, future researchers might be able to hone in on specific genetic reasons for human diseases, thanks to the shocking adaptations of some fish. 

Source Study: Science Advances — Divergent cis-regulatory evolution underlies the convergent loss of sodium channel expression in electric fish (science.org)