ARS Study Provides a Better Understanding of How
Mosquitoes Find a Host By
Dennis O'Brien March 9, 2010
The potentially deadly yellow-fever-transmitting Aedes aegypti
mosquito detects the specific chemical structure of a compound called
octenol as one way to find a mammalian host for a blood meal,
Agricultural Research Service (ARS)
Scientists have long known that mosquitoes can detect octenol, but
this most recent finding by ARS entomologists
Bohbot explains in greater detail how Ae. aegypti—and possibly
other mosquito species—accomplish this.
Dickens and Bohbot, at the ARS
Insect Biocontrol and Behavior Laboratory in Beltsville, Md., have shown
that Ae. aegypti taps into the "right-handed" and "left-handed"
structural nature of octenol, which is emitted by people, cattle and other
mammals. This ability to detect the "handedness" of molecules has been shown in
mammals, but the discovery is the first case of scientists finding out how it
works in an insect, according to the researchers.
When they hunt for a blood meal, mosquitoes hone in on a variety of
chemicals, including carbon dioxide, lactic acid, ammonia and octenol. Octenol
is one of many carbon-based compounds that have a molecular structure that can
take on either a "right-handed" or "left-handed" form. Each form is a mirror
image of the other, and a form's "handedness" is determined by how its
molecular bonds are assembled.
The scientists used frog eggs to help them make their discovery. They
injected RNA from Ae. aegypti into the frog eggs, allowing the egg
membranes to mimic the mosquito's ability to detect octenol. Then they attached
microelectrodes to the frog egg cell membranes, passed octenol over them and
recorded the electrical signals stimulated by the odors.
They ran the tests using both the right- and left-handed forms of
octenol. The scientists found heightened electrical activity when the membrane
was exposed to the right-handed form, and weakened activity when it was exposed
to the left-handed form.
There are many natural compounds that can take on either a
right-handed or left-handed form. While the effects of those differences on
many plants and animals remains a mystery, the report, published in PLoS ONE, shows the effects
of octenol's dual structure on the yellow fever mosquito and adds to
scientists' understanding of how mosquitoes sense the world around them. It
also may open the door to speedier development of better mosquito repellents
and traps, according to Dickens.
The team's research is being funded by the
Department of Defense Deployed War
Fighter Protection Research Program.
ARS is the principal intramural scientific research agency of the
U.S. Department of