Natures wonders: fruit fly pheromones and odors (Introduction)

by David Turell @, Monday, October 12, 2015, 17:05 (1641 days ago) @ David Turell

Male fruit flies can identify certain food odors and mark the spot with pheromones, hoping to attract females and stat a family in a food rich area:

"The team then tested different combinations of flies during the apple cider vinegar phase and the clean air phase, and found that males alone were the ones depositing the pheromone, and that it was attractive to both males and females.

"To learn whether the flies were indeed smelling the pheromone or just tasting it, the researchers used a series of mutant flies that lacked one set of sensory detectors—taste or smell—or the other. It turned out that the fruit flies' aggregation behavior depended on their sense of smell.

"Potter says identifying the specific pheromone itself was "a bit trickier," but the team relied on what was known about pheromones generally and guessed that they could dissolve it off the plates using a solvent called hexane. The researchers then made sure that the hexane wash contained the pheromone by painting an E on the bottom of the enclosure with it and watching the flies' behavior. They then captured on video the flies recreating the E by spending more time along that letter-shaped "paint" than anywhere else in their enclosure.

"Potter says that a recent study showed that male fruit flies make four different airborne pheromones whose chemical makeup dissolves in hexane. To pinpoint which one was responsible for the phenomenon they were seeing, the research team used a technology called gas chromatography-mass spectrometry to figure out the molecular makeup of the hexane wash. The result was 9-tricosene, whose fruit fly function was unknown at the time. But when they painted 9-tricosene in an E shape on the enclosure's floor, the flies aggregated in a similarly patterned way to what the researchers had seen with the hexane wash.

"Intrigued by the finding, Potter says, the research team wondered if 9-tricosene could be stimulating more than just fly get-togethers, since other critical behaviors—such as courtship and egg laying—also occur at food sources.

"To find out, the researchers modified their fly enclosure slightly by adding a thin layer of gel to the bottom so that females could lay eggs. After males laid down 9-tricosene in response to food odors, females laid five times more eggs in the same quadrant.

"Further experiments found that 9-tricosene activates the receptor protein Or7a that is found on about 20 olfactory (smell) neurons in the fly's antennae. "The activated receptor sends a signal to the brain, which can trigger behavioral responses," says Potter. "What's interesting is that these olfactory neurons, because of where they are found on the fly's 'nose,' were previously considered unlikely suspects to respond to pheromones, so this finding opens up a whole new set of questions about how animals behave and react to their environments."

Comment: This looks like a learned behaviour that became an instinct. Family planning with food source.

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