August 31, 2013
Mosquitoes Detect Human Scents Better During The Nighttime
redOrbit Staff & Wire Reports – Your Universe Online
In research that could change the way we protect ourselves from mosquitoes, scientists from the University of Notre Dame's Eck Institute for Global Health have discovered the disease-carrying insects are able to smell major human host odorants better during the nighttime hours.The study, which appears in this week’s edition of the open-access journal Nature: Scientific Reports, used an integrative approach to investigate the mosquito’s ability to smell throughout the 24-hour day. The researchers used proteomic, sensory physiological, and behavioral techniques to examine the role of odorant-binding proteins (OBPs) -- a major chemosensory family of mosquito proteins -- in the everyday regulation of olfactory sensitivities in anopheles (malarial mosquitoes).
The researchers believe OBPs in the mosquito’s antennae and mouth parts function in a way to concentrate odorant molecules and help carry them to the insect’s actual olfactory receptors, leading to odorant detection. They then revealed the daily rhythmic protein abundance of these OBPs, and found the anopheles had higher concentrations of these scent-detecting substances in their sensory organs at night.
Associate Professor Giles Duffield and Assistant Professor Zain Syed of the Department of Biological Sciences, as well as Research Assistant Professor Matthew M. Champion of the Department of Chemistry and Biochemistry, were members of the research team. Samuel Rund, a doctoral candidate in Duffield’s laboratory, and Nicolle Bonar, a visiting researcher and undergraduate student from Queens University of Ontario, were lead authors on the study.
According to the authors, they used mass spectrometry to quantify the protein abundance in the sensory organ of the mosquitoes, as well as electroantennograms to determine the response induced by host odorants during different parts of the day. The way the peak protein abundance, the level of olfactory sensitivity, and the biting behavior of the mosquitoes coincide reflect the level of control of the insect’s physiology. The OBP levels and the sensitivity to smells are at their highest when needed during the nighttime and lower when not needed in the day.
“This was an exciting opportunity to bring many people and techniques together to make some really fascinating findings on the mosquito's ability to smell humans, its host,” Rund said. “Just think, during the day the mosquito is sleeping and doesn't need to smell you. But when the sun goes down, the mosquito's olfactory system becomes extra-sensitive, and she is ready to smell and then bite you.”
The research, which was supported in part by the National Institutes of Health-funded Indiana Clinical and Translational Sciences Institute as well as the University of Notre Dame's Center for Rare and Neglected Diseases, was a follow-up to previous work by the team in which they used genomic tools to reveal 24-hour rhythmic patterns of gene expression, including some involved in olfaction. That study was published in the journal BMC Genomics back in April of this year.