UT Austin Researchers Identify Crazy Ants’ Defense Against Fire Ant Venom


The rise of invasive “crazy ants” have quickly become a force to be reckoned with in the southwestern U.S., with their growing numbers and highly adaptive biological make-up leading to an alarming displacement of the the fire ant population throughout the region. Because this markedly rapid shift in ant dominance is bearing out a palpable ecological change, scientists in Texas have been engaged in trying to better understand what has led to these so-called crazy ants’ ability to dominate an otherwise robust ant species like the fire ant.

According to researchers at University of Texas at Austin, who published a new study last week on crazy ants in the journal Science Express, the secret weapon for crazy ants’ victories over their fire ant adversaries is involves secreting a compound that neutralizes fire ant venom — the first known example of an insect with the ability to detoxify another insect’s venom.

Anyone who has ever been stung by a fire ant is well aware of how painful their venom can be. But where a fire ant’s venom is merely painful to a human, to other insects, the sting is lethal. Scientists believe that the fire ant’s topical insecticide is, pound for pound, two to three times as toxic as DDT when the insect wields it on other ants and insects.

Strangely, however, the fire ant’s venom has no effect on crazy ants.

UT researchers observed an elaborate detoxification procedure, wherein “the exposed crazy ant secretes formic acid from a specialized gland at the tip of its abdomen, transfers it to its mouth and then smears it on its body,” according to a recent press release. The crazy ants’ detoxification process was found by researchers to be so effective that those crazy ants infected with fire ant venom boasted a 98 percent survival rate — making them invincible to a fire ant attack. The fascinating video above documents a one-on-one confrontation between a crazy ant and fire ant wherein the entire process is revealed.

“As this plays out, unless something new and different happens, crazy ants are going to displace fire ants from much of the southeastern U.S. and become the new ecologically dominant invasive ant species,” said Ed LeBrun, a research associate with the Texas invasive species research program at the Brackenridge Field Laboratory in UT Austin’s College of Natural Sciences.

The full consequences of this new ant realignment in the southwest is still not completely understood. However, researchers generally agree that the crazy ants’ ability to dominate the insect world will eventually lead to an overall decrease in arthropods — insects, spiders, centipedes and crustaceans — which could in turn reduce food sources for birds, reptiles and other animals. Crazy ants can also do industrial damage to human structures as well, such as eating through electrical wires.

Dr. LeBrun and his team discovered the behavior after observing a battle over a dead cricket between the two any species at a Texas field site, wherein the fire ants attempted to defend the  find with large numbers protecting the food source. ”The crazy ants charged into the fire ants, spraying venom,” said LeBrun. “When the crazy ants were dabbed with fire ant venom, they would go off and do this odd behavior where they would curl up their gaster [an ant’s modified abdomen] and touch their mouths.”

Later experiments at the Brackenridge Field Laboratory in Austin put the crazy ants’ detoxification process into better focus, as LeBrun and researchers were able to locate and test the formic acid detoxifier by testing crazy versus fire ant match ups with and without the ability to detoxify. Without the ability to apply the detoxifying compound to themselves, about half of the crazy ants dabbed with fire ant venom died. Among a control group of crazy ants with unsealed glands, on the other hand, 98 percent survived.

Researchers still do not have an answer for how the formic acid renders imported fire ant venom nontoxic, though it is believed that the substance prevents the venom from penetrating the outer layers of a crazy ant’s exoskeleton. Regardless, this evolution is only one is long series between the two spies, whose rivalry in the ecosphere has most likely been going on for millennia.

Original story – http://bionews-tx.com/news/2014/02/16/ut-austin-researchers-identify-crazy-ants-defense-fire-ant-venom/

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