Eels Can Genetically Modify Nearby Fish With Their Electrical Pulses

In laboratory experiments, gene transfer occurred in 5 percent of zebrafish larvae that were near eels when they discharged electricity

Close-up shot of electric eel swimming under water
Electric eels can discharge up to 860 volts of electricity. Mark Newman via Getty Images

In the lab, researchers regularly use electricity to deposit medicine, DNA, bacteria or other substances into cells. This process is known as electroporation, and it works by creating temporary openings, or pores, in cell membranes that the DNA can enter through. Scientists use electroporation for a range of applications, from developing new vaccines to creating genetically modified plants.

Now, researchers have discovered that electric eels may be causing the same phenomenon to occur in nature. In the lab, these unusual creatures can release enough electricity to genetically modify nearby fish larvae, scientists report this month in PeerJ—Life and Environment.

Electric eels have very poor eyesight, so to navigate their freshwater surroundings, they emit a weak electrical signal that functions like radar. When they come across a tasty morsel, such as a fish or a crustacean, they produce a high-voltage electrical discharge to stun their prey. The eels can release up to 860 volts of electricity, making them the most electric animals on Earth.

Scientists in Japan wondered whether these electric shocks might be enough to cause electroporation and, thus, affect the cells of nearby creatures. Bodies of water are full of environmental DNA, also known as eDNA, or tiny amounts of genetic material shed by plants and animals. Some of this eDNA, they hypothesized, might be making its way into the cells of other organisms, courtesy of the eels.

“I realized that electric eels in the Amazon River could well act as a power source, organisms living in the surrounding area could act as recipient cells and environmental DNA fragments released into the water would become foreign genes, causing genetic recombination in the surrounding organisms because of electric discharge,” says study co-author Atsuo Iida, an aquatic life scientist at Nagoya University in Japan, in a statement.

'Shocking' discovery: Electricity from electric eels may transfer genetic material to nearby animals

To test this idea, they set up a laboratory experiment with a tank full of water. Scientists placed zebrafish larvae in the tank, then added a DNA solution with a gene that would make fish glow fluorescent green. Next, they put an eel in the tank and fed it an anesthetized goldfish, which prompted it to discharge 185-volt pulses of electricity, reports New Scientist’s Melissa Hobson.

One day later, some of the zebrafish larvae began to glow green, suggesting the fluorescent DNA solution had been transferred from the water into their cells. The glow lasted for between three and seven days. When the team examined the zebrafish larvae, they found that gene transfer had occurred in 5 percent of them.

Black background with glowing green shapes
Some of the zebrafish larvae began glowing green. Shintaro Sakaki

The study has limitations—it was conducted in a lab, not in the wild, for example—but the researchers say their findings suggest eels can cause electroporation. In theory, this means that electric eels could be contributing to the genetic modification of other species in the wild. Organisms that are swimming or floating near eels might be evolving in unexpected ways because of this process.

In the future, the team hopes to conduct additional research into whether electric eel discharges can have a similar effect on much smaller organisms, such as plankton and bacteria.

It remains unclear whether the genetically modified zebrafish larvae could pass along the acquired genes to their offspring. This is unlikely, because DNA degrades quickly, but it is not impossible. In nature, this could mean that “discharges by electric eels could eventually generate new species or increase diversity,” says Tadej Kotnik, a biomedical engineer at the University of Ljubljana in Slovenia who was not involved in the research, to New Scientist.

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