Fecal Attraction: Fruit Flies Poop To Lure Others

Scientists in Japan have discovered that fecal deposits carry the fruit fly’s pheromone flag, increasing the flies’ chances of mating.

AsianScientist (Aug. 15, 2018) – In a study published in Current Biology, scientists in Japan have discovered how fruit flies communicate through pheromone-laced feces.

Many species from flies to mammals use signaling molecules called pheromones to attract mates and communicate socially. These pheromones may waft off the body or be excreted in urine.

In the present study, researchers at Japan’s RIKEN Center for Brain Science wanted to find out how fruit flies communicate via pheromones. They discovered that pheromone-laced fecal landmarks, rather than the bodies of flies themselves, are strong attractors for fellow flies.

To make their observations, the scientists allowed fruit flies to move around untethered in a small arena equipped with both visible light and thermal imaging capabilities. They were interested in how male and female flies respond to the male pheromone cVA which activates only a specific class of odor-sensing neurons. In genetically-engineered flies, these neurons glow when activated.

Observing male flies in the arena, the researchers found that odor-sensing neurons were triggered most strongly by locations with fly droppings rather than in areas where there were other flies.

“We have seen cases where the odor-sensing neurons respond only after a [fecal] marking,” said Associate Professor Hokto Kazama of RIKEN. “The closer the flies are to these fecal landmarks, the more bioluminescence we see.”

Male flies will circle the perimeter and deposit droppings, with a tendency to re-visit and spend more time around the marked regions, the researchers noted. Flies with blocked odor-sensing neurons did not show this attraction.

In another experiment with a male and female fly, the female’s droppings were not attractive. The male’s markings, on the other hand, were attractive to both sexes, even during courtship when a female is being chased by a male. Fecal landmarks thus function as a social hub, indicating the identity of the marking fly and increasing mating chances.

The system for monitoring bioluminescence has applications beyond fruit flies. Any neural recording, especially of small animals, that would traditionally require wires or tethering can now harness the power of these glowing brains, giving researchers a real-time look at activity during social communication.

“Emerging genome editing technologies combined with bioluminescent probes are giving us a powerful window into observing natural behavior and how it arises in the brain,” said Kazama.

The article can be found at: Mercier et al. (2018) Olfactory Landmark-Based Communication in Interacting Drosophila.


Source: RIKEN; Photo: Pixabay.
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