This Electric Fish Sees Their Mates ‘See’ Images

This Electric Fish Sees Their Mates ‘See’ Images

By Jack Tamisiea

With a trunk-like snout, an enormous brain and brilliant movements, the freshwater elephantnose fish seems straight out of a science-fiction novel. But the unique characteristics of these oddities are their ability to emit and sense electricity. They use electric currents to identify prey and potential mates in the muddy river bottom where they live.

Now scientists have discovered that fish can increase this power by working together. In a paper published Wednesday in the journal nature, A team of researchers has discovered that elephantnose fish pick up on the electrical signals of their pulsating peers to collectively sense the world around them. This can expand the fish’s perceptual abilities, helping them sense prey items and potential adversaries from further away.

“We are excited to see that the electric pulses [of other fish] is not just some background noise,” said Nathaniel Sawtell, a neuroscientist at Columbia University and a co-author of the new paper. “Fish actually use the pulses of other fish to their advantage.”

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Sawtell studied the neural wiring of Peters’ elephantnose fish (Gnathonemus petersii) for several years. These fish, found in freshwater rivers and lakes throughout central and western Africa and with tree-like extensions of their mouths, are brainiacs. They have the highest brain-to-body weight ratio of any vertebrate, including humans.

All this brain power helps harness the fish’s electrical capabilities. Although they cannot match the high voltage output of electric eels and stingrays, elephantnose fish can create pulses of charge from an electric organ in their tail. They emit these pulses into the environment in a similar way to how bats and dolphins use sound waves. As the signals bounce off nearby objects, tiny electroreceptors in the fish’s skin pick up distortions in the electric field.

Researchers have long studied how elephantnose fish perceive their own electric currents. But less work has been done to determine how these fish understand pulses from other fish, especially when they gather in social groups.

To learn more about how elephantnose fish are affected by each other’s electrical signals, Sawtell worked with his postdoctoral research associate Federico Pedraja to create a computer simulation. Their goal was to model how the electrical environment changed when many elephantnose fish were in close proximity to each other.

The researchers discovered that the simulated elephantnose fish actually tuned in to the electrical pulses of their neighbors. As one fish creates an electric “image” of a nearby object, the other fish in the simulation immediately get a visual of what the first animal feels. If a group of three elephantnose fish approach the same object, the fish will receive slightly different electrical images of that object at essentially the same time, allowing them to “see” their surroundings in greater detail.

The fish’s ability to switch these senses without being disturbed by interfering electrical signals is surprising, says Sarah Skeels, a zoologist at Queen Mary University of London, who has studied the electrical perception of elephantnose fish. for his Ph.D. “You’d think that other fish could cause interference, but as they showed, it seems like it can actually enhance some aspect of something that’s not apparent in individual fish,” said Skeels, who doesn’t involved in new learning. .

Teamwork also expanded the fish’s range of perception up to three times more. “By using the pulses of other fish, an individual can see the electrical properties of objects that are further away,” Sawtell said. “Electric fields fall off dramatically over distance, so having an electrical field emitted by another nearby animal can greatly expand its sensing range.” People have used a similar technique to hone radar, which senses distant objects more accurately when electromagnetic pulses move between multiple emitters and receivers.

The researchers corroborated their modeling results with recordings of the neural activity of elephantnose fish. They found that the region of the animals’ oversized brain that controls the electrosensory system was able to tune in to both signals from an elephantnose fish and external electric currents, including the pulses of other fish. The team also observed how the elephantnose fish behaved when they were put together in tanks. The researchers observed the fish lined up in straight or vertical formations. According to the computer model, these positions appear to help maximize collective sensing capabilities.

While this is the first known example of collective sensing in electric fish, it may not be the last, Skeels said. He says there are hundreds of other species of electric fish, including some highly social species. For example, researchers recently discovered that electric eels can hunt in packs and synchronize their shocks to stun prey. He thinks it’s plausible that some kind of collective sense could be “a key sensory element of the world’s electric fish.”

According to Sawtell and Pedraja, the elephantnose fish’s collective sensing could help scientists develop artificial sensing technologies in things like underwater vehicles. But first the researchers need to get a more detailed glimpse of what’s going on inside the noggins of these strange fish.

“We don’t yet know how the fish brain actually processes complex streams of information,” Sawtell said. “We want to understand how evolution has improved the brains of these fish over millions of years to solve this problem.”