Ancient Neuropeptides Shape Modern Ant Parental Care

When it comes to raising young within insect societies, it takes a village—typically a queen and the workers. Ants divide and conquer to complete tasks: Young ants care for the larvae while older ants transition to foraging outside the nest for food. These behaviors piqued the interest of Daniel Kronauer at The Rockefeller University, where he delves into the functional genetics and neuroscience behind the social evolution and behavior of ants.

To study these behaviors, Kronauer uses clonal raider ants as a social insect model system. As their name suggests, these ants are genetically identical—ideal for Kronauer’s team to probe the neuropeptides that play a role in parenting and age-related behaviors.

In a new study, published in Nature, Kronauer and his colleagues identified two neuropeptides in the ant brain that change with age and modulate parental behavior in opposite directions: One increased an ant’s tendency to nurse and be close to larvae, while the other promoted foraging.¹ The two neuropeptides are evolutionarily ancient and are known to regulate feeding in solitary animals.² Rather than losing their original role, Tomas Kay, a postdoctoral researcher in Kronauer’s group, explained that these two peptides simultaneously controlled parenting. These findings provide insight into how complex social behaviors may have evolved by co-opting existing neuromodulators.

First, the team compared the behavior of young (12-day-old) and old (four-month-old) ants. They placed ant colonies within a two-chamber system. The nest chamber contained larvae, and the other side was a foraging area. Young ants spent roughly twice as much time tending larvae, whereas older ants spent around three times longer foraging. This behavior persisted even in a one-ant and one-larvae set up within a narrow corridor assay. These results suggest that clonal raider ants exhibit age-based division of labor.

Then, to identify the potential neuropeptides driving this behavior, the researchers built a comprehensive library of the clonal raider ant neuropeptidome. They identified 70 unique neuropeptides and synthetized 61 of these molecules to see how each affected ant behavior. Of these, 24 neuropeptide candidates altered the amount of time ants spent with larvae; however, two stood out—neuropeptide F (NPF) and allatostatin A (AstA). NPF promoted nurse-like behavior typically seen in young ants, while AstA increased the tendency for forager-like behavior.

The researchers also found that levels of these neuropeptides in the brain naturally shift with age. As ants transitioned from nursing larvae to foraging, the levels of NPF declined while AstA increased.

To investigate whether these behaviors could be manipulated, the researchers used RNA interference to reduce each neuropeptide in ants. This reversed the behavioral effects, providing direct evidence that these signaling molecules help determine the age-related division of labor within ant colonies.

In addition, NPF and AstA are evolutionarily ancient. In solitary animals, such as flies, NPF and AstA act as readouts for nutritional status and regulate feeding. To find out whether this ancestral function was still conserved in clonal raider ants, the researchers assessed ant behavior under fed and starved conditions. When ants were starved, their NPF levels increased while AstA levels decreased. This is a pattern seen in solitary animals. Not only that, but these shifts also influenced brood care behavior. Food-deprived ants stayed with larvae, while fed ants explored the environment.

“It’s interesting that they had two neuropeptides with reversed functions,” said Susanne Foitzik, an evolutionary biologist and behavioral scientist at Johannes Gutenberg University Mainz, who was not involved in the study. “It demonstrates that there is somewhat of a flexibility. I can manipulate a colony…fast forward so a young individual will start to forage, or backwards.”

The team’s study underscores the developmental and age component to the division of labor among clonal raider ants. “A lot of people [might] think of them as separate phenomena, but this kind of work shows you that on a molecular level, they’re actually deeply connected,” said Kronauer.

Together, the findings add to growing evidence that the evolution of complex social behaviors often relies on co-opting ancient neuromodulators originally involved in feeding, growth, and reproduction. Rather than abandoning their ancestral functions, these molecules have acquired new roles that help coordinate parental care and social organization.

Kronauer added, “Ultimately, we might be able to have a real understanding of how insect societies actually evolved. And so, I think this study is one of the first [that] gives you a first glimpse of that.”