They may be tiny, but Argentine ants can kick some ant butt.
This
invasive species has nearly wiped out native
ants in California
Now scientists have discovered a way to turn one of the ants'
strongest weapons into a weakness.
By altering the identifying
chemicals coating the ants' bodies, researchers turned
typical cooperative behavior into an ant-family feud.
Super colony
Like most ants, the Argentine ant (Linepithema humile)
relies on
chemical tags to identify friend or foe [photo].
The chemicals are waxy and can't evaporate into the air
like other
animal communication chemicals called pheromones. The
ants must make physical contact to smell them.
Ants of the World
Some 20,000 ant species crawl the world. In this new
Image Gallery, see a few of them, from photographer
and entomologist Alex Wild at the University of Arizona.
Wild has more ant images on
his web site.
Scientists suspect that a single colony of the ants,
originally from South America, hitched a ride to the
United States in the 1890s aboard multiple cargo ships
that docked in Louisiana.
Since most of the Argentine ants now in California
descended from a single colony, they are pals and wear
matching chemical coats. Unlike in South America, where
there are several smaller ant colonies, most of the
Argentine ants in California belong to "one gigantic super
colony that stretches basically from San Diego all the way
to San Francisco, so you could take an ant from San Diego
and put it in a nest in San Francisco and they would treat
them the same as if they are family," said study team
member Robert Sulc, a graduate student at the University
of California, Irvine.
That's a problem for native ant species that are fewer
in number.
Even though they are just an eighth of an inch long,
their sheer numbers have allowed the invasive ants to kick
out or kill [photo]
other ant colonies in California, study team member
Kenneth Shea, an organic chemist at the university, told
LiveScience.
To try and outsmart the ants, the research team, led by
UC Irvine evolutionary biologist Neil Tsutsui, whipped up
batches of chemical compounds with a similar structure to
those coating the Argentine ant colonies. When they coated
one of the colony ants with the new compound, the other
ants began attacking it as an enemy.
"Our preliminary results strongly suggest that by
manipulating these chemicals on the exoskeleton, one could
disrupt the cooperative behavior of these ants and, in
essence, trigger civil unrest within these huge colonies,"
Shea said.
The work was described today at a meeting of the
American Chemical Society in San Francisco.
"I think that this is really important, because they
are finally starting to crack the code of how Argentine
ants recognize and communicate with each other," said
Brian Fisher, curator of entomology at the California
Academy of Sciences. Fisher was not involved in the study.
Dizzying experiment
Getting the chemical treatment was dizzying. First,
Tsutsui and his team coated the inside of a vial with the
chemical. They plopped an ant into the tube and spun it in
a machine for 90 seconds to make the chemical stick.
"After all that shaking it's a little bit wobbly but
usually it's still alive," Sulc said. "Then, we put it
back into the Petri dish with ten of its friends from the
same colony and then we observe how aggressive they are
toward him."
The other ants immediately attacked, using their
large mandibles, or jaws, to bite and tear off its
legs, Sulc said.
The invasion of Argentine ants could ripple through the
ecosystem, affecting more than just the native ants. For
instance, the Coastal Horned lizard relies exclusively on
the native ants for food, and as these ants dwindle so
could the lizard.
Until now, neither pesticides nor trapping has thwarted
the spread of the Argentine ants.
The scientists hope the strategy could be used in the
future to finally check the spread of the Argentine ants.
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