Planet Earth

Is an Ant Colony's Caste System Determined by Epigenetics?

80beatsBy Joseph CalamiaAug 27, 2010 10:00 PM


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What does it take to be a long-living queen? Change your gene expression, say researchers who analyzed both worker ant and queen ant genes in two ant species--making the humble bug the second social insect (after the bee) to get sequenced. Their results appear today in Science and suggest that epigenetic changes--molecular switches that alter gene expression--may mean the difference between the queen's long life, and the workers' short one. Epigenetic changes don't actually modify the underlying genetic code, instead they're carried out by mechanisms that act like on and off switches for genes. That could explain how a queen and worker ant can have the same genetic blueprints but very different lives.

“Ants are extremely social creatures and their ability to survive depends on their community in a very similar way to humans,” says [co-author Danny] Reinberg, who is also a member of the NYU Cancer Institute. “Whether they are workers, soldiers or queens, ants seem to be a perfect fit to study whether epigenetics influences behavior and aging.” [Arizona State University]

The two types of ants live in very different societies. The carpenter ants (Camponotus floridanus) live together in the thousands with one queen, and once the queen dies the whole colony is a goner. The jumping ants (Harpegnathos saltator) live in smaller groups of around 60 and when a queen dies they fight to take over the egg-laying throne. The researchers analyzed ants in the same and different castes in both species, looking at gene expression and epigenetic differences--for example when a molecule known as a methyl group attaches to part of the genome. They spotted those methyl groups in both ants' genomes, suggesting that this methylation may be a mechanism that shapes ant behavior. Among the jumping ants, they also noted that when a new female replaced a queen she increased her expression of two genes also associated with human longevity.

"We think that's pretty exciting," says Shelly Berger, a geneticist at the University of Pennsylvania Medical School in Philadelphia and another lead author on the study. "It means that we are going to be able to understand how these epigenetic systems are involved in these behavioural transitions." [Nature News]

The researchers hope that sequencing the genomes of more ant species will deepen their understanding of the epigenetic influence on biology and behavior. Also, they note that ants are a bit easier logistically to study than rats and mice. Christopher Smith, a cell biologist who wasn't involved with the study, comments:

"Ants' true strength is an epigenetic system," Smith says. Mice also have a complex epigenetic profile, but they can be more troublesome for bigger studies because, as Smith notes of experimental animals, "once you have a backbone, you have a lot of paperwork and expense.... What we have been lacking," Smith notes "is a good invertebrate social model system." Although the honeybee genome was published in 2006, ants, he explains, "are a lot easier to keep in a lab." [Scientific American]

Related content: 80beats: Parasite-Infested Zombie Ants Walked the Earth 48 Million Years Ago 80beats: Ant’s Chemical Signal Tells Nest Mates: “I’m Not Dead Yet” 80beats: Finally, a Predator to Control the Notorious Cane Toad: Meat Ants? 80beats: Tricky Caterpillars Impersonate Queen Ants to Get Worker Ant ProtectionImage: Design by Robert Bonasio; Photography by Jurgen Liebig

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