In the case of an ant species, workers duel in order to establish a new leadership after the death of their queen. While these sparring games stretch over a month, changes in behavior and gene expression in the first three days of the duel can predict exactly who will triumph, according to a New York University study published in the journal Genes & Development.
"Despite ongoing social upheaval in ant colonies following the loss of the queen, the winners of these duel tournaments are easy to determine," said Claude Desplan, silver professor of biology at NYU. "Our results may provide evidence of adaptability in reproduction and aging, as workers who win the duel, or 'pseudoqueens', are given the ability to lay eggs and live much longer than the average worker ant. This suggests suggest that the environment is changing are able to dramatically affect the structure of a society. "
The caste system in social insects creates a division of labor with insects who specialize in certain tasks. The queen is responsible for reproduction while the workers tend the colony – looking after the young, foraging and hunting, cleaning and defending the nest.
In many insect communities, when the queen dies, the entire colony dies with her due to lack of reproduction. In the case of Indian jumping ants (Harpegnathos saltator), however, a "box change" occurs after the queen's death. While the queen is alive, she secretes pheromones that prevent female worker ants from laying eggs. However, when she dies, the workers feel the lack of pheromones and begin to struggle with each other to take the lead.
The ants take part in duel tournaments and fight each other with their antennae in games that can last more than a month. While most ants quickly return to their usual jobs during the tournament, the winners become pseudo-queens – also known as gamergates – and acquire new behaviors and roles. With this transition, their life expectancy increases dramatically (from seven months to four years) and they lay eggs for the colony to survive.
In their study in Genes & DevelopmentNYU researchers examined changes in the social behavior of Indian jumper ants and associated changes in gene expression in the early stages of the transition from worker to pseudoqueen.
They found that after just three days of duel, the winners can only be accurately predicted on the basis of dueling behavior. The workers who triumphed and became pseudoqueens had a much higher duel – about twice as much sparring in the first five days – while the others who remained workers did less duels and did other tasks such as cleaning and hunting.
"Despite the fact that duel tournaments last several weeks, we were able to predict which ants would become pseudoqueens in just three days," said Comzit Opachaloemphan, a graduate student in the Department of Biochemistry and Molecular Pharmacology at NYU Grossman School of Medicine and a lead author the study.
Researchers compared biological samples and gene expression from dueling and non-dueling ants, and then determined the changes associated with the transition from worker to pseudoqueen. Molecular analysis found that the brain may be driving the duel and early caste determination in the ants, while other tissues provide clues to the brain.
The researchers found that the first genes that responded to the loss of the queen were present in the brain, suggesting that the lack of queen pheromones perceived by the olfactory system affects the brain's neurohormonal factors. These changes in the brain then lead to altered social behavior and hormone-mediated physiological changes in other parts of the body, including the ovaries.
"Both behavioral and molecular data – particularly changes in gene expression in the brain – show that new pseudoqueens are quickly identified after the social structure of a colony has been disrupted by the loss of the queen," said study author Danny Reinberg, of Terry and Mel Karmazin Professor in the Department of Biochemistry and Molecular Pharmacology at NYU's Grossman School of Medicine and a researcher at the Howard Hughes Medical Institute.
Further authors of the study are the co-first authors Giacomo Mancini and Nikos Konstantinides as well as Apurva Parikh, Jakub Mlejnek and Hua Yan. The research was supported by a Collaborative Innovation Award from the Howard Hughes Medical Institute (# 2009005), the National Institutes of Health (R21-GM114457, R01-EY13010, R01-AG058762, and F32AG044971), EMBO (365-2014), and Human Frontier Science Program (LT000122 / 2015-L).