March 9, 2010
The potentially deadly
aegyptimosquito 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
Scientists have long known that
mosquitoes can detect octenol, but this
most recent finding by ARS entomologists
Joseph Dickensand Jonathan Bohbot
explains in greater detail how Ae.
aegypti—and possibly other mosquito
Dickens and Bohbot, at the ARS Invasive
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
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
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
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
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
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 Agriculture.