Fish can sense fear in other fish and be scared too, study finds

WASHINGTON — Our ability to care about others may have very, very ancient origins, a new study suggests.

It may have been deeply rooted in prehistoric animals that lived millions of years ago, before fish and mammals like us diverged on the tree of life, according to researchers who published their study Thursday in the journal Science.

“Some of the mechanisms that underlie our ability to experience fear, or to fall in love and fall in love, are clearly very old pathways,” said Hans Hofmann, an evolutionary neuroscientist at the University of Texas at Austin, who did not participate in the research. .

Scientists are generally reluctant to attribute human feelings to animals. But it is generally accepted that many animals have moods, including fish.

The new study shows that fish can sense fear in other fish and then be afraid too – and that this ability is regulated by oxytocin, the same brain chemical that underpins the capacity for empathy in fish. ‘male.

The researchers demonstrated this by deleting genes linked to the production and uptake of oxytocin in the brain of zebrafish, a small tropical fish often used for research. These fish were then essentially antisocial – they failed to detect or change their behavior when other fish were anxious.

But when some of the altered fish were injected with oxytocin, their ability to sense and reflect other fish’s feelings was restored – what scientists call “emotional contagion.”

“They react to other people who are scared. In that regard, they behave like us,” said neuroscientist Ibukun Akinrinade of the University of Calgary, co-author of the study.

The study also showed that zebrafish will pay more attention to fish that have already been stressed – a behavior the researchers likened to consoling them.

Previous research has shown that oxytocin plays a similar role in fear transmission in mice.

The new research illustrates the “ancestral role” of oxytocin in transmitting emotions, said Rui Oliveira, behavioral biologist at Portugal’s Gulbenkian Institute of Sciences and co-author of the study.

This brain processing “may have already been in place around 450 million years ago, when you and I and these little fishes last had a common ancestor,” Hofmann explained.

Oxytocin is sometimes thought of as a “love” hormone, but Hofmann said it’s more like “a thermostat that determines what’s socially salient in a particular situation – activating neural circuits that can make you run away from the danger or engage in courtship behavior.”

This could be fundamental to the survival of many animals, especially those that live in groups, said Stony Brook University ecologist Carl Safina, who was not involved in the study.

“The most basic form of empathy is contagious fear – it’s a very valuable thing for staying alive, if someone in your party spots a predator or other danger.”