Most insects use chemical signals for a wide variety of functions, such as communicating species and sex. Social insects, such as ants that live in colonies, can also differentiate the different castes — workers, queens, and drones — according to the chemical cues.
If these chemicals could be isolated, they could theoretically be exploited to control pest species and could possibly replace insecticides. However, isolating these chemicals and determining their absolute configurations and functions has been challenging because the chemicals occur in complex mixtures which are hard to separate.
Now entomologists and chemists at the University of California, Riverside have devised a straightforward method for purifying these compounds that could result in new “green” methods for controlling pest species, like ants, by disrupting the organization of their colonies.
“In so-called social insects that live in large colonies, such as ants and bees, these chemicals have additional functions,” said co-author Jocelyn G. Millar. “The queen in these colonies, for example, uses the chemicals to prevent her workers from laying eggs of their own, ensuring that she remains the only reproducing female in the colony.”
The researchers devised a technique that allowed them to isolate 36 pure hydrocarbon molecules from the complex chemical blends of 20 randomly-chosen insect species. After the compounds could be conclusively identified, the effects of the individual chemicals could be tested. Their technique is described in the Proceedings of the National Academy of Sciences.
The research team’s efforts were complicated by the fact that these chemicals can occur in “right-handed” or “left-handed” forms. The two forms share the same molecular structure, but are mirror images of each other.
“This is critical information for biological activity, because if you have the wrong form, it is like trying to put your right hand into a left-hand glove,” Millar said. “The wrong form of the chemical will simply not fit into its biological receptor.”
The team was able to solve this problem by showing that all 20 insects that were tested had — regardless of species, sex, or life stage — the right-handed form of these chemicals.
“This suggests strongly that nearly all insects are likely to produce the R form of these chemicals,” Millar said. “Knowing this will be of great help in unraveling what these signals do and how they work.”
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