Ants exposed to air pollution face aggression from their own nestmates, according to a new study that sheds more light on the harmful effects of human activity on ecology.
Ants recognise their nestmates from molecules produced by their glands and one set of these compounds, called alkenes, is crucial for the colony's unique odour.
These compounds, with carbon-carbon double bonds, are picked up by ants immediately after hatching and tend to degrade on exposure to some chemicals.
When two ants come in contact, they compare each other’s smell with the respective odour of their colony.
If they recognise the odour, they are regarded as nestmates and treated kindly. If the odour profiles do not match, they tend to become more aggressive towards each other.
The new study tested whether increasing the levels of ozone, a chemical known to degrade alkenes, in the atmosphere altered the odour signature of ants.
Researchers exposed ants from six species for nearly 20 minutes to an ozone concentration of 100 parts per billion, a level often measured in polluted areas during the summer, and returned them to their colonies.
In five of the six species, the ozone-exposed ants were targeted with aggression by their nestmates.
The findings indicate that even slight increases in ozone pollution can degrade key molecules that ants use to recognise each other and thereby negatively impact numerous species.
“We had expected that ozone exposure would affect the recognition of nest mates, as we knew that ants carry at least small amounts of easily degradable alkenes on their bodies,” said Markus Knaden, an author of the study published in the journal PNAS. “However, we were surprised by the dramatic change in behaviour after ants had been exposed to ozone.”
In spite of their small quantities, some alkene compounds may be critical for ants to recognise their kin.
In some cases, researchers found adult ants in ozone-polluted colonies were distant from their larvae compared to those in ozone-free environments. And many larvae in such nests also died.
"Oxidising pollutants such as ozone and nitrogen oxides are often discussed because of their harmful effects on humans,” Bill Hansson, another author of the study, said.
“However, we should also be aware that these manmade pollutants can also cause significant damage to our ecosystems.”
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