African fish uses electrical signals to navigate murky waters

The elephant-nose fish – scientific name Gnathonemus petersii – uses electrical signals to navigate through the water and find food, which is a particularly useful skill given that it lives in murky African rivers. Since us humans don’t use electricity to find our way in the world, this system can be a bit of a mystery to scientists. But researchers at Columbia University have just found a very cool quirk in this fish’s electric navigation system.

In the journal Neuron, the scientists have published evidence that the elephant-nose fish’s ability to “see” an “electrical image” of its surroundings requires it to filter out the fish’s own electrical interference.

This fish has two specialized systems to help it sense its surroundings. The passive system is responsible for the tiny electric signatures of everything that lives in its habitat, while an active system voluntarily emits quick pulses of electricity. These electrical pulses are used to both communicate with other fish and allow the individual to sense its environment by producing an electrical image.

“The fish’s own electrical pulses cause large neural responses that interfere with the passive system,” says Nathanial Sawtell, a neuroscientist at Columbia University. “Our work shows how changes in neural connections produce negative images to cancel out this interference.”

Earlier studies have postulated that this fish is able to generate these negative images, but this study presents the first evidence of this theory and the functional importance of this trait.

“We needed to determine whether being able to predict its own electrical signals would help the fish better detect environmental cues,” says Sawtell. “So using both neural recordings and behavioral experiments, we showed that these predictions known as negative images actually do help the fish sense external signals related to hunting prey.”

By exposing the fish to a drug that interfered with the formation of negative images, the researchers found that they essentially blinded the fish to external electrical signals.

“An important part of this work has been the integration of experimental and theoretical approaches to understanding neural circuits,” explains Sawtell. “From here, we’re trying to take the lessons we’ve learned from the electric fish and apply them to related systems, including the mammalian cerebellum and auditory system.”

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By Connor Ertz, Earth.com Staff Writer