Clever Trick Helps Electric Fish Ignore Their Own Zaps, Study Finds

It's hard to imagine a noisy fish, but pop an electrode in the tank of elephantfish and you get an earful. Shutterstock/Pavaphon Supanantananont

Some fish communicate using electric pulses to create small zaps that send messages to other animals. You might think it would be carnage trying to get anything across with all that zapping going on, but new research published in the Journal of Neuroscience has uncovered how these animals block out their own signals and only listen to those around them.

Elephantfish, from the family mormyridae, might appear to the uninitiated as if they drift about their tank in blissful silence. Pop in an electrode, however, and your speakers will come alive with a buzzy din of nattering fish using electric currents to communicate with each other. Some species use short sharp zaps while others send longer more delayed messages. They need to be able to filter out their own racket if they’re to glean anything from their environment, but for some time scientists had no idea how.

This new study reveals that the fish use a cool trick to essentially tell their brains to ignore their own messages. This happens as the result of a corollary discharge, which is basically a negative copy of their original message and acts as an inhibitory signal. Rather than having to block all sensory inputs while speaking, this discharge allows the fish to keep on listening while rejecting its own zaps. If you’ve ever accidentally spoken over key dialogue in a film, you’ll appreciate the benefit of such an adaptation.

The inhibitory signals are also matched to the fishes’ specific zap type, so short sharp zappers get short sharp discharges and the slow zaps get slow discharges. The behavior prevents the fish from missing out on important environmental information, which unlike talking over a movie can result in the loss of a mating opportunity or even death if they miss a signal that a predator’s around.

Corollary discharges have been investigated since the 1950s. They’ve been linked to insights into medical science, particularly psychiatric diseases such as schizophrenia, and it’s hoped that better understanding their function could have broader implications for understanding the evolution of brains.

“I love strange creatures, including electric fish,” said Matasaburo Fukutomi, a postdoctoral fellow working on the study. “We can only feel electricity as pain, but we never sense electricity as the fish does… Surprisingly, electrosensory systems share a lot of general features with other sensory systems. I am very excited to be studying these fish.”

[H/T: Futurity]

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