A Shocking Fish Tale Surprises Evolutionary Biologists Unrelated lineages of electric fish all use the same small set of genes to create their voltage, a genetic search shows. Maybe the same genes could one day power pacemakers, bioengineers suggest.

A Shocking Fish Tale Surprises Evolutionary Biologists

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The electric eel can deliver powerful shocks, up to 600 volts. That's enough to kill a person. This eel is perhaps the most famous electric fish, but there are hundreds of others, too, that produce weaker electric fields. NPR's Nell Greenfieldboyce reports on a new study that shows the surprising way in which these fish became electrified.

NELL GREENFIELDBOYCE, BYLINE: Michael Sussman studies electric eels in his lab at the University of Wisconsin Madison. He says a six foot long electric eel is basically a six inch fish attached to a five and a half foot cattle prod.

MICHAEL SUSSMAN: So all of the intestines and the stomach and all that stuff is right close to the head. And the rest of the electric eel is an electric organ. It's just a beautiful tissue.

GREENFIELDBOYCE: The tissue of this organ is a lot like muscle, but it can't contract. Its cells are big and have all sorts of features that let them pump out electric city without shocking the fish. The cells are stacked together like batteries in a flashlight, and they all fire simultaneously. It's about 100 volts per foot of eel. Sussman says he's been shocked by eels a couple of feet long.

SUSSMAN: And it's kind of like putting your finger in an electric outlet. You know, it's very unpleasant, and you kind of pull your finger away.

GREENFIELDBOYCE: A shock like this can stun or kill prey. Other electric fish use weaker fields to navigate through murky waters or to talk to each other in a weird, staticy way.


JASON GALLANT: That's an interaction between a breeding male and a breeding female. So they're electrically singing to each other, actually.

GREENFIELDBOYCE: Jason Gallant is an electric fish expert at Michigan State University. He takes their electrical energy and converts it to sound.


GALLANT: Each fish has kind of a distinctive type of sound, like the species itself.

GREENFIELDBOYCE: Now, it's amazing that evolution invented an organ for making electricity even once. But in fact, evolution did it six separate times in completely different fish. How is that possible? Gallant, Sussman and a bunch of other scientists wanted to know, so they analyzed all the genes of the electric eel then also looked at gene activity in other electric fishes from unrelated families. What they discovered was shocking.

GALLANT: They're using the same genetic tools to build their electric organs in each lineage independently.

GREENFIELDBOYCE: Again and again, evolution used the same set of about 30 genes.

GALLANT: It seems like there are limited ways to build an electric organ, and that's sort of a surprising find because you wouldn't necessarily have expected that.

GREENFIELDBOYCE: The findings are described in the journal, Science. Lindsay Traeger works in Sussman's lab. She says one dream is to use this new information to create an electric organ in a creature that doesn't normally have one.

LINDSAY TRAEGER: I definitely think that it's a possibility in the future. I'm not sure how far off it is, but it's probably closer than we can imagine.

GREENFIELDBOYCE: She and her colleagues have been tossing around some possibilities. Maybe people could have little electric organs to power medical devices.

TRAEGER: Perhaps one application of something like this could be creating a bio-battery for the use of pacemakers - actually create a bio-battery in this person's body so we no longer have to go in and replace this battery when it's gets old.

GREENFIELDBOYCE: Before that, of course, researchers would have to do a lot more work. One major step would to be taken an ordinary lab fish and tweak its genes to make it electric. Nell Greenfieldboyce, NPR News.


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