Canadian researchers have discovered how to make a certain kinds of ants develop into "supersoldiers" with huge oblong heads and giant vicious jaws.
The findings are significant because they show there is dormant genetic potential that can be invoked by changes in the environment and locked in place for a very long time, said lead author Ehab Abouheif, a McGill University biology professor, whose research was published Friday in the journal Science.
The authors suggest that hanging on to ancestral developmental toolkits can be an important way for organisms to evolve new physical traits.
"Birds with teeth, snakes with fingers and humans with ape-like hair – these are ancestral traits that pop regularly in nature," Abouheif said. "But for the longest time in evolutionary theory, these ancestral traits were thought to go nowhere … the Barnum and Bailey of evolution. So they've been an unappreciated source of evolutionary variation."
Typically, supersoldier ants are biological anomalies that occur rarely in nature and only in limited geographical regions. But the McGill researchers found these supersoldiers in unexpected regions and also created them by manipulating hormones.
Pheidole (big-headed) ant colonies contain millions of ants, including minor workers and soldiers. Depending on the food ants are fed, certain hormones are triggered in the ant larvae and they either develop into soldiers or minor workers.
Then there are supersoldier ants that block their nest entrance with their extra-large heads and fight with invading ants during army ant raids.
Abouheif and his team unexpectedly found supersoldier ants in the Pheidole species in Long Island where they aren't normally seen. They were then able to artificially induce them in the lab by by dabbing the larvae with juvenile hormone, indicating that environmental cues can switch on the genetic machinery that produces supersoldiers.
"The kind of environmental stressors that evoke this dormant potential are there all the time, so when the need arises natural selection can take hold of the potential and actualize it," said Abouheif.
"So what we're showing is that environmental stress is important for evolution because it can facilitate the development of novel phenotypes. Any time you have a mismatch between the normal environment of the organism and its genetic potential you can release them – and these things can be locked in place for 30 to 65 million years."