New research has revealed the genetic secrets behind the defiant longevity of termite queens.
Typically, there is an inverse relationship with fertility and aging. The more offspring a species produces, the more likely the female is to have a relatively short life. Conversely, less fertile species tend to live longer.
Social insects and specifically the termite queen defies the pattern.
"Macrotermes queens are the most reproductively successful terrestrial animals," biologist Judith Korb, a professor at the University of Freiburg's Institute of Zoology in Germany, said in a news release.
The queen of the largest known termite species, Macrotermes bellicosus, lays as many as 20,000 eggs a day and can live upwards of 20 years. Workers, on the other hand, have the same genome at their disposal, but produce no offspring and live no longer than a few months.
Researchers compared the gene activity in the cells of young and old termites, as well as in kings, queens and workers.
"We were very surprised by the result," Korb said. "We found hardly any differences between old and young individuals in queens and kings, but for the workers they were enormous."
Older kings and queens expressed almost the exact same genes at the beginning and end of a five-year span. Over the span of a few months, however, scientists measured thousands of differences in the genes expressed by workers.
Most of the new genes found expressed in older workers were what scientists call "jumping genes." These genes replicate indiscriminately throughout the genome, causing mutations and turning off other genes. Previous studies have linked jumping genes with the aging process.
"We already know from other model organisms that jumping genes can be related to aging," said Korb. "But the question is: why are they inactive in queens and kings?"
Journey to the center of the...termite nest? Hard to believe this termite queen will produce almost 165 million eggs in her lifetime! Credit: National Geographic
In Macrotermes bellicosus colonies, kings and queens are responsible only for reproduction. Workers farm fungus that yields nitrogen, the termite's energy source, while soldiers guard the underground nest. The operation features a sophisticated division of labor.
In the new study, published this week in the journal PNAS, researchers argue the genetic differences can be better understood when the termite colony is interpreted as the superorganism that it is.
In a multicellular organism, the cells responsible for reproduction are called the germline. Germline cells have the signaling pathways that incapacitate jumping genes, protecting the health of the organism's offspring. In workers, this "piRNA signalling pathway" is down regulated, or suppressed.
In kings and queens, which act as the germline of the superorganism, the pathway is active, preventing aging.
"We will down-regulate the piRNA signalling pathway in queens in the laboratory, and we expect that they will then also age," said Korb.
Researchers also want to study termites with less specialized social structures to see if division of labor really is the secret to a queen's
fertility and long lifespan.