Are all ants created equal? They sure look the same, and for the most part, even act the same. So how do they tell one another apart? Researchers now believe they have identified the exact mechanism that allows ants to tell friend from foe.
It should be noted that researchers have known that ants use their sense of smell to identify a foe, almost like a dog would. In some cases relatively mindless workers and soldiers will reject an unrecognizable invader Spartan style, kicking or grappling them from great heights.
However, how exactly they do this, and whether or not they can likewise distinguish different castes (worker, soldier, drone, queen) within their own colony via smell has long been disputed. And yet, we do know that this distinction occurs, with individuals even regulating one another to various posts, including toilet duty!
"Until now, very little was understood about how ants use olfactory detection of pheromones to recognize individuals belonging to different castes or different colonies in their societies," research lead Anandasankar Ray, a neuroscientist and entomologist at the University of California, Riverside, said in a statement. "To address this problem, we decided to focus our attention on the worker ants' antennal neurons and their responses to hydrocarbons on the cuticle. What we wanted to study was how ants detect sophisticated pheromones which organize their behaviors efficiently." (Scroll to read on...)
Ray and his team reportedly exposed workers to one distinct hydrocarbon and trained them to recognize it as 'friendly' by associating it with a sugar reward. The researchers then introduced a foreign but very similar hydrocarbon into the same closed environment. Without fail, the worker ants flocked to the friendly smell while avoiding the unfamiliar one. They theorize that this would likewise work with invaders, where a learned threat to a hive would prompt an aggressive response to the trained hydrocarbon and indifference for the addition. The results of the study were published in the journal Cell Reports.
What's more, the researchers learned that ants have very sensitive 'noses,' capable of distinguishing even the most similar of odors. As a result, Ray likens an ant's body odor to that of a barcode. Products from the same store all have very similar barcodes, but slight differences can tell a clerk where everything belongs. Likewise, a product from another store will have a very different barcode, and will go unrecognized or even get thrown out. (Scroll to read on...)
[Credit: University of California, Riverside / Kavita Sharma ]
And the need for a high-end 'code scanner' could explain why ants have a sophisticated olfactory receptor system with the largest odorant receptor gene family (more than 400 genes) known in insects.
"The evidence suggests that this large number of receptors is probably needed to smell out the complex bouquet of hydrocarbons each individual emits," Ray added.
Still, this is not to say the smell sense of ants is infallible. In the deserts bordering Arizona and Mexico, biologists know of two distinct ant species that actually survive off deceiving one another, regularly bumbling into one another's colony to have mistaken sex sessions with the enemy queen. Likewise, the larvae of Maculinea butterflies reportedly 'sing' to a colony's workers, tricking them into caring for it until maturity. How exactly these ants remain so oblivious of invaders remains a mystery - one that Ray and his team may help solve in the future.
"We are [now] closing in to finding the functional roles [key] receptors, and, in particular, finding the olfactory receptors that detect pheromones from the queen who regulates much of the order in the colony," he said.
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