Fluid from ant pupae is used as “milk” to nourish developing ants
Insects living in a colony are more like cells in tissue rather than separate species just sharing a room together; their interactions with one another create a beautiful symphony. Researchers have recently uncovered a social connection amongst ants of all developmental stages, adults, larvae, and pupae (an immobile stage similar to a butterfly’s chrysalis during which ants change from larvae to adults).
According to the study published in Nature, the pupae produce an undiscovered fluid that is quickly consumed by adults and larvae. The colony’s well-being appears to depend on the prompt consumption of this nutrient-packed fluid, since the larvae require it for growth, and the pupae die from fungal diseases as the fluid accumulates around them if neither the adults nor the larvae consume it.
According to Daniel Kronauer, the Stanley S. and Sydney R. Shuman Associate Professor at The Rockefeller University, the way the ants utilize this fluid generates a dependence across distinct developmental phases. It just goes to illustrate how well-maintained an ant colony can be.
The busy environment in which ant colonies function makes it impossible for scientists to see the multitude of interactions among ants that are essential to the colony’s regular functioning. Orli Snir, a postdoc in Kronauer’s lab and the study’s first author said that these interactions lay at the very center of understanding insect communities, but, because of the intrinsic obstacles, they haven’t been examined extensively.
Snir decided to take a head-on approach to this issue by studying ant colonies in order to deduce the underlying principles of social relationships. She did this by isolating ants at various ages from the rest of the colony to see how they would react.
Her initial observations were the accumulation of fluid surrounding the isolated pupae. Pupae seldom, if ever, produce fluid, and this was previously unknown in ants. Pupae soaked in this solution often succumbed to fungal diseases. The pupae only made it to maturity when Snir physically removed the fluid. The ant colony was obviously preventing a buildup of pupal fluid.
Kronauer, Snir, and coworkers used dye tracing studies to determine the fluid’s path, and after they learned that both adults and larvae were consuming the fluid, they began investigating the fluid’s chemical makeup and the effects on ants that refrained from drinking it.
The researchers traced the fluid back to a process called molting, which is universal across insects and involves the removal of the cuticle so that new skin may develop. In order to preserve resources, non-social insects recycle their molting fluid, whereas ant pupae provide it to their nestmates.
Psychoactive chemicals, hormones, and components of royal jelly, which honeybees save for developing queen bees were also discovered in the fluid. Not only do ants of all ages appear to love the fluid, but young ant larvae require it; without it, growth is hindered and many die within the first four days of life.
According to Kronauer, the larvae depend on the fluid almost like a baby relies on milk in the first few days after hatching. The adults consume it in large quantities, and its effects on their metabolism and physiology are unknown but likely significant.
Kronauer believes the approach of reusing molting fluid into a nourishing signaling fluid is extremely conserved, since his team identified the same basic phenomena across each of the five major ant subfamilies after doing the original investigation with clonal raider ants. It’s possible that it developed just once, well back before ants ever existed.
The ant colony has been compared to a superorganism due to the coordinated efforts of its many individual members. Like cells in a living tissue, ants exchange chemical signals to pass along information. Both pheromones, which communicate information in the immediate, and social fluids, which can influence metabolic and behavioral changes over longer periods of time, fall under this category. This concept of ant colonies as interconnected superorganisms is enriched by the discovery of the pupal social fluid and its role in linking adults, pupae, and larvae.
Snir explains that pupal social fluid is the driving force behind a crucial and unrecognized interaction network in ant communities. There was previously unknown interdependence between the larval and pupal stages.
The team plans to investigate the implications of this molting fluid on the colony’s functioning in future research. Kronauer is especially curious about whether or not molting fluid influences adult behavior, and whether or not it plays a role in determining which caste ant larvae will become.
Snir argues that the study just gives a look into the complex social networks of insect society. The researchers’ ultimate objective is to learn all they can about the neurological and molecular mechanisms behind social organization and their evolutionary roots.
Daniel Kronauer. (2022). The pupal molting fluid has evolved social functions in ants, Nature. DOI: 10.1038/s41586-022-05480-9. www.nature.com/articles/s41586-022-05480-9
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