Electric fish: sharing sensory secrets

Electric fish extend the range of what they can each see by sharing sensory information among themselves...

When electric elephantnose fish congregate in small groups, they can sense their environment much better and over a significantly greater distance than an individual fish in isolation. This collaboration improves their ability to find food and navigate.

These animals dwell in dark and murky riverwater, where light-based vision is generally unhelpful. Instead, they use a neurological "radar screen", a bit like the echolocation techniques used by bats and dolphins, by tuning in to the electric fields around them. Specialised organs on their skin both emit and sense these fields, enabling the fish both to transmit electrical "pings" and, simultaneously, probe their surroundings. This is called electro-location. 

Incredibly, the fish can also share among themselves the information they glean from this electrical sensing system in a process scientists call "collective sensing".

To model this, Columbia University's Nathaniel Sawtell and his team used a computer simulation to mimic the electric signals the fish emit. They found that when multiple fish are together, they each receive different electric views of the same scene, which helps them detect objects further away.

“In groups, the fish can actually see further away. So an object that would be outside the range of the electro-location of the fish when it was on its own was actually clearly visible to the fish when another nearby fish was also emitting electrical impulses,” explains Sawtell.

Neural studies of the brains of the fish also proved the fish can amplify their electro-location range up to 3 times as a group. Recordings from the electrosensory part of the brain show that the fish responded to both, their own electrical impulses and to external impulses.

But how do they do this?

“It’s worth noting that these fish we’re studying have enormous brains,” says Sawtell.

Indeed, electric fish have the biggest brains relative to their body weight than any other animal. But unlike similarly-cerebral humans, it is the brain region known as the cerebellum in these fish that accounts for the lion's share of the animal's big brains. 

“We’ve often wondered what kind of intelligence these animals have that relies on the cerebellum,” says Sawtell.

It is possible that these fish use this part of the brain to understand the shared information they receive. Sawtell speculates that, in order to act on this information quickly, the fish need to have knowledge about their group members, how they relate to one another, and how they’d move in a space. The cerebellum, given its role in processing movement, timing and sequences of actions, could be interpreting that information.

This discovery raises some exciting questions about how these fish communicate and cooperate. It also has implications beyond marine life. Understanding how these fish work together could inspire new technologies, like better underwater sensors or even medical imaging techniques.