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Arthur T Knackerbracket has processed the following story:

Fruit flies—Drosophila melanogaster—have a complicated relationship with carbon dioxide. In some contexts, CO₂ indicates the presence of tasty food sources as sugar-fermenting yeast in fruit produces the molecule as a by-product. But in other cases, CO₂ can be a warning to stay away, signaling an oxygen-poor or overcrowded environment with too many other flies. How do flies tell the difference?

Now, a new study reveals that fruit fly olfactory neurons—those responsible for sensing chemical "smells" such as CO₂—have the ability to talk to each other through a previously undiscovered pathway. The work provides insights into the fundamental processes by which brain cells communicate with one another and also gives new clues to solving the longstanding mysteries about fruit flies and CO₂.

[...] However, this olfactory crosstalk depends on the timing of CO₂ cues. When CO₂ is detected in fluctuating pulses, such as a wind-borne cue from a distant food source, the CO₂-sensing olfactory channel sends a message to the channels encoding esters, signaling to the brain that delicious food is upwind. However, if CO₂ is continually elevated in the local environment, for instance from a rotting log, this crosstalk is quickly shutoff, and the CO₂-sensitive neurons signal directly to the brain to avoid the source.

More information: Dhruv Zocchi et al, Parallel encoding of CO2 in attractive and aversive glomeruli by selective lateral signaling between olfactory afferents, Current Biology (2022). DOI: 10.1016/j.cub.2022.08.025

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