Discovery Of Natural Odors Could Help Develop Mosquito Repellents (via ScienceDaily)
When fruit flies undergo stress, they emit carbon dioxide (CO2) that serves as a warning to other fruit flies that danger or predators could be nearby. The fruit flies are able to detect the CO2 and escape because their antennae are equipped with specialized neurons that are sensitive to the gas.
But fruits and other important food sources for fruit flies also emit CO2 as a by-product of respiration and ripening. If the innate response of the fruit fly is to avoid CO2, how then does it find its way to these foods?
Anandasankar Ray, an assistant professor in the Department of Entomology, and Stephanie Turner, his graduate student, now provide an answer to the paradox.
They have identified a new class of odorants – chemical compounds with smells – present in ripening fruit that prevent the CO2-sensitive neurons in the antennae from functioning. In particular two odors, hexanol and 2,3- butanedione, are strong inhibitors of the CO2-sensitive neurons in the fruit fly….
“CO2 emitted in human breath is the main attractant for the Culex mosquito to find people, aiding the transmission of these deadly diseases,” Ray said. “In our experiments we identified hexanol, and a related odor, butanal, as strong inhibitors of CO2-sensitive neurons in Culex mosquitoes. These compounds can now be used to guide research in developing novel repellents and masking agents that are economical and environmentally safe methods to block mosquitoes’ ability to detect CO2 in our breath, thereby dramatically reducing mosquito-human contact.”
Perceptual Rivalry: Nostrils Alternate To Process Competing Odors
When the nose encounters two different scents simultaneously, the brain processes them separately through each nostril in an alternating fashion.
For the study, 12 volunteers sampled smells from two bottles containing distinctively different odors. One bottle had phenyl ethyl alcohol, which smells like a rose, and the other had n-butanol, which smells like a marker pen. The bottles were fitted with nosepieces so that volunteers could sample both scents simultaneously — one through each nostril.
During 20 rounds of sampling, all 12 participants experienced switches between smelling predominantly the rose scent and smelling predominantly the marker scent. Some experienced more frequent and drastic switches than others, but there was no predictable pattern of the switch across the whole group of volunteers or within individuals.
Chen said this “binaral rivalry” between the nostrils resembles the rivalry that occurs between other pairs of sensory organs. When the eyes simultaneously view two different images — one for each eye — the two images are perceived in alternation, one at a time. And when alternating tones an octave apart are played out of phase to each ear, most people experience a single tone that goes back and forth from ear to ear…. (more @ ScienceDaily)
