'Crazy Ants' Rapidly Replacing Fire Ants By Surviving Normally Deadly Venom
Fire ants, which are native to northern Argentina and southern Brazil, dominate most other ant species because of their venom. But they are rapidly being displaced by members of a different ant species called "crazy ants". Large areas in the south-eastern United States, which were earlier fire ant nesting sites, have now been invaded by crazy antsbecause they can produce a chemical compound called formic acid, which neutralizes fire ant venom.
When fire ants sting, they inject a venom (often used as a topical insecticide), which is painful for humans and often fatal to other ant species. When stung by fire ants, crazy ants almost always survive. What antidote protects the crazy ants from the fire ant's venom? Scientists studying these ants have observed that when stung, the crazy ant secretes formic acid from a specialized gland at the tip of its abdomen, according to a press release Thursday. It then smears this formic acid on its body, which protects it from the fire ant's toxic venom.
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In an experiment conducted at the Texas Invasive Species Research Program at t UT Austin's College of Natural Sciences, fire ants and crazy ants were put together in vials. Crazy ants showed a 98 percent survival rate even after being exposed to the fire ant's venom. To further test the effectiveness of the formic acid, which protects the crazy ants from being poisoned, the scientists sealed the formic acid producing glands, of a few crazy ants, with nail polish. Thus, unable to coat themselves with the detoxifying agent, the crazy ants smeared with fire ant venom died.
Although, the exact nature in which the formic acid neutralizes the effect of the red ant venom has not yet been established. One possible theory is that it coats the crazy ant's exoskeleton and prevents the venom from penetrating inside.
An observation at a Texas field site got Ed LeBrun, who spearheaded this research, interested in the survival mechanism of the crazy ants. He found two populations of red ants and fire ants fighting over a dead cricket. The fire ants were guarding the cricket, their potential food resource, in large numbers. "The crazy ants charged into the fire ants, spraying venom. 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", said LeBrun. This led LeBrun to the conclusion that the crazy ants were using a kind of detoxifying agent.
Researchers say that this detoxifying agent allows the crazy ants to counter any attack that might come from the fire ants over food resources and nesting sites. "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," says Ed LeBrun.
Their population can only be checked by human intervention or extreme climatic conditions such as severe cold or arid soil. Research has shown that when allowed to proliferate crazy ants affect the population of arthropods such as insects, spiders, centipedes, and crustaceans thereby reducing the food sources for birds, reptiles, and other animals thus causing ecological damage.
Since colonies of crazy ants spread slowly, they can be localized. The only way they can spread long distances is when transported in potted plants or in vehicles which have been parked in areas where there are nests of crazy ants.
Source: LeBrun, E. Jones, N. et al. Crazy ants dominate fire ants by neutralizing their venom. Science Express. 2014.
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