Ant pupae secrete a never-before-seen liquid that adults and larvae drink immediately to keep the entire colony healthy, a new study finds.
Life in an ant colony is a symphony of subtle interactions between insects that act in concert, like cells in tissue, rather than individual organisms that inhabit a colony.
The previously unknown social interaction connects colony connections with ants throughout their developmental stages (adults, larvae, and pupae) and a dormant stage not unlike a butterfly’s chrysalis, where ants transition from larva to adults.
published work, Naturereveals that the health of the entire colony appears to depend on rapid consumption of this nutrient-packed fluid. The larvae need it to grow, and if the adults and larvae are unable to drink it, the pupae will die from fungal infections as fluid builds up around them.
“The way ants use this fluid creates a dependency between the different stages of development,” says Daniel Kronauer, associate professor at Rockefeller University. “It just shows to what extent the ant colonies really work as an integrated unit.”
Ant colony social interaction
The ants move in the hustle and bustle of a dense colony, creating challenges for researchers trying to observe the various interactions between ants that keep the colony running smoothly.
“These interactions are central to understanding insect societies, but have not been systematically investigated because of the inherent challenges,” says first author Orli Snir, a postdoc in Kronauer’s lab.
To address this problem directly, Snir decided to reverse engineer the ant colony to identify some of the fundamental principles that guide social interactions. To do this, he removed ants at different developmental stages from the colony and studied how social isolation affects the insects.
“For the first few days after hatching, the larvae rely on the liquid almost as much as a newborn baby relies on milk.”
One of the first things he noticed was fluid buildup around the isolated pupae. Insects do not normally secrete fluid during pupal stage, and such fluid has not been observed in ants either. This fluid was prone to fungal infections that eventually killed the pupae. The pupae only survived to adulthood when Snir manually removed the fluid. Obviously, the ant colony was somehow preventing pupal fluid from accumulating.
Kronauer, Snir and colleagues conducted dye-tracking experiments to figure out where the liquid was going, and when they discovered that the adults and larvae were drinking it, they set out to explore the liquid’s composition and observe what happened to the ants that didn’t participate.
The researchers discovered that the fluid is derived from a conserved process found in all insects, called moulting, in which insects shed their old cuticles to grow. Unsocial insects recycle molting fluid to conserve nutrients, while ant pupae share it with their nest mates.
Ant colony ‘superorganism’
The researchers found that the liquid is rich in nutrients, as well as psychoactive substances, hormones, and some components found in royal jelly, which honeybees reserve for queen bee larvae. And while ants of all ages seem to enjoy liquid, young ant larvae need it – those deprived of liquid in their first four days of life cannot grow and many eventually die.
“For the first few days after hatching, the larvae rely on the liquid almost as much as a newborn baby relies on milk,” says Kronauer. “Adults drink voraciously, too, and we’re confident it affects metabolism and physiology, although it’s not clear what it does to adults.”
After Kronauer’s team conducted the initial study in clonal raider ants, they found the same general phenomenon in each of the five major ant subfamilies; “It probably evolved once, early in ant evolution, or even before ant evolution.”
The ant colony is sometimes called a super-organism – a unified entity made up of many organisms working in harmony. Indeed, ants transmit information by exchanging chemical signals in ways similar to how cells communicate in tissue.
These often include pheromones that convey short-term information and social fluids that have the potential to influence long-term metabolic and behavioral changes. The discovery of pupal social fluid and its role in connecting adults, pupae and larvae adds context to the understanding that ant colonies are interconnected superorganisms.
“Pupal social fluid is the driving force behind a central and hitherto overlooked network of interactions in ant communities,” says Snir. “This reveals a new aspect of interdependence between larvae and pupae and between pupae and adults.”
In future work, the team will further explore the effects of this molting fluid on the inner workings of the colony. Kronauer is particularly interested in determining whether molting fluid plays a role in deciding the caste of ant larvae, and whether and how it influences the behavior of adults.
“This study provides only a glimpse into the complex interaction networks of insect communities,” says Snir. “Our long-term goal is to gain a deep understanding of the neural and molecular mechanisms that govern social organization and how these mechanisms evolve.”
Source: Joshua Krisch on behalf of Rockefeller University