Ants attack their nest-mates because pollution changes their smell

Chiara Marchisio — Mon, 02 Feb 2026 20:00:07 +0000

Harvester ants attack nest-mates whose scent they don’t recognise

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Common air pollutants like ozone and nitric oxide can change the way ants smell, prompting their nest-mates to attack them as if they were intruders.

Ants recognise their comrades by scent, and when they encounter an ant whose smell they don’t recognise, they respond aggressively, biting and sometimes killing the trespasser. But ozone, a greenhouse gas produced by cars and industrial activities, can break down the structure of alkenes, chemicals that make up part of the colony-specific scents.

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at the Max Planck Institute for Chemical Ecology in Jena, Germany, and his colleagues knew from previous work that ozone-induced changes in alkenes can impair the way insects communicate with each other. They witnessed fruit flies mate with the wrong species and pollinators such as tobacco hawkmoths if their scent had been altered by ozone.

To test the impact on ants, Knaden and his colleagues set up artificial colonies of six ant species. They removed one individual ant from each and put it in a glass chamber filled with various concentrations of ozone, some of which matched levels measured in Jena in summer. When they put the ant back, the others attacked it.

“I did not expect it, I have to say,” says Knaden. “Because knowing that alkenes are such a minor part [of the ants’ scent], we knew that whatever we did with ozone would only change maybe 2 per cent or 5 per cent of the blend.”

In the wild, this kind of behaviour could make a colony less efficient, he says, even if the ants are not killed, but designing experiments to capture these effects will be complicated.

at The Rockefeller University in New York, who wasn’t involved in the study, says alkenes are very important in nest-mate recognition, so the aggressive reactions didn’t shock him.

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‘We’re precipitating an extermination rather than an extinction event’

Alkenes are involved in other ant behaviours like trail following and communication between larvae and adults. The study found that, when exposed to ozone, adult clonal raider ants (Ooceraea biroi) can neglect their larvae, so these ozone-induced changes have the potential to disrupt more aspects of ant life – and the wider ecosystem too.

“If you took the ants out of most terrestrial ecosystems, they would probably collapse,” says Kronauer. This is because ants have crucial ecological roles. They disperse seeds, move soil and have mutually beneficial relationships with many organisms.

Insect populations are plummeting worldwide, and this study adds to a growing body of research that points to air pollutants as one of the factors behind the decline. Knaden says that even though the ozone pollution levels we are experiencing might not yet be harmful to humans, “we just should know that what we are doing has additional costs that we have maybe not thought about before.”

Journal reference:

PNAS

Our brains play a surprising role in recovering from a heart attack

Chiara Marchisio — Tue, 27 Jan 2026 16:00:30 +0000

The brain responds after a heart attack

Science Photo Library / Alamy

Following a heart attack, the brain picks up and acts on signals that come directly from sensory neurons located in the heart. The discovery suggests there is a feedback loop, which involves the immune system as well as the brain, that has an important role in recovery. “The body and the brain do not exist in isolation. There is immense crosstalk between different organ systems, the nervous system and the immune system,” says at the University of California, San Diego. Augustine and his colleagues knew from previous work that the heart and the brain are linked by cardiac sensory neurons that regulate blood pressure and .

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So they set up an experiment to understand if similar nerves are involved in the response to heart attacks. They made a mouse’s heart transparent by getting rid of the lipids it contains through a cutting-edge technique called , induced a heart attack by blocking blood flow, and then tracked which heart nerves were most called into action. They found a previously undiscovered cluster of sensory neurons that stem from the vagus nerve and wrap tightly around the heart ventricle’s thick muscular wall, especially where the tissue was damaged by the lack of blood flow. Before the heart attack, there were just a handful of these nerve fibres. After the heart attack, though, the fibres increased severalfold, says Augustine, suggesting the heart actually triggers these neurons to grow following injury. When Augustine’s team genetically manipulated these nerves to turn them off, preventing them sending signals back to the brain, the heart quickly healed. “The injured area becomes really, really small,” says Augustine. “The recovery was remarkable.” After heart attacks, patients often have to undergo surgery to restore blood flow to the heart and prevent further tissue damage. A future drug that targets the newly found neurons, Augustine says, could give patients an alternative, particularly if surgery isn’t available immediately.

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The researchers also noticed the signals produced by these nerves travelled to cells in a region of the brain that is activated in response to stress, sending the mouse into fight-or-flight response. This, in turn, activated the immune system, directing immune cells to travel to the heart. The immune cells form scar tissue that repairs the injured heart muscle, but too much scarring can alter the muscle’s function and lead to subsequent heart failure. By blocking this immune response early, Augustine and his colleagues showed another way for the mice to heal after a heart attack. Experiments in recent decades have hinted at communication between the heart, the brain and the immune system during heart attacks. What’s changed is that scientists now have the tools to identify changes in a level of detail that reaches specific populations of neurons, says at George Washington University in Washington DC, who wasn’t involved in the study. “This gives us really exciting opportunities to develop new therapies for patients that have heart attacks,” he says, which could potentially include gene therapies.

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Doctors regularly prescribe beta blockers to help patients heal from the tissue damage caused during a heart attack. These findings help elucidate that beta blockers may work by targeting part of the nervous and immune system feedback loop that is activated by a heart attack. “We may already be intervening on [the newly discovered] pathway,” says at the University of Oxford, who wasn’t involved in the study. However, Choudhury adds, this pathway probably doesn’t exist in isolation and is part of a complex picture of responses that we don’t completely understand yet, which involves other immune cells and signals. Factors like genetic and sex differences, or conditions like diabetes and hypertension could also potentially affect how the newly identified response plays out. This means that, before designing new drugs targeting the pathway, there has to be a way to determine if and when it is active in the wider population, says Choudhury.

Journal reference:

Cell

Chiara Marchisio, Author at ��è����Ƶ

Ants attack their nest-mates because pollution changes their smell

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