Researchers have discovered that ants secrete a milk-like liquid that feeds other members of the colony.
The research, published in Nature on 30 November, reveals that as pupae–an otherwise inactive developmental stage–ants produce a nutrient-rich fluid that is consumed by both adults and larvae.
Larvae that have just been hatched depend on this fluid for growth and survival, much like how newborn mammalian mammals depend on milk. The fluid can build up and become contaminated with fungi if the larvae and adults of ants don’t consume it. This can kill the pupae.
” We identified a mechanism that unites colony, binding an ant across developmental stages–adults larvae and pupae- forming a coherent entity called the superorganism,” said Orli Snir (a biologist at Rockefeller University in New York City).
” It is quite surprising that no one else has noticed this before,” says Patrizia d’Ettorre, an ethologist from Sorbonne Paris North University in France. “The pupae were thought to be useless because they are immobile. They spin a cocoon around themselves in some species. They don’t eat and are just moved about by [ant] workers. So they [wouldn’t] contribute anything for ant society.” This paper proves that this is false .”
Snir and her colleagues made the discovery by observing clonal raider ants (Ooceraea biroi) kept in isolation at different stages of their life cycle, to investigate what makes ant colonies so integrated.
Researchers were shocked to find fluid droplets on isolated ant pupae. The fluid built up and drowned the pupae, but it was removed.
By injecting blue food coloring into the pupae, and following its path, the researchers found that adult ants consume the fluid as it is released. They also carry the larvae to the pupae. This prevents the fluid from accumulating. Snir says that the adults are taking care of the pupae, cleaning them and putting the larvae on the pupae to eat.
The team tested the molecular composition of the fluid and identified 185 proteins that were specific to it, as well as more than 100 metabolites such as amino acids, sugars and vitamins. The moulting fluids are fluids that larvae shed as they become pupae. Adria LeBoeuf (a biologist at University of Fribourg in Switzerland) says that it is an opportunistic recycling of the ants inside the colony… and a metabolic division of labor.
The researchers also found pupal’milk” in five species of the five largest ant subfamilies. This suggests that it may have played a role in the evolution and structure of ant social networks. Daniel Kronauer, a Rockefeller University biologist, said that it could have evolved shortly after ants became eusocial.
The team is now studying the effects of pupal secretions on larvae and adults in terms both of behaviour and physiology. Kronauer says that the fluid they have access to may influence whether larvae become queens or workers.
Karsten Schonrogge is an ecologist at UK Centre for Ecology & Hydrology, Wallingford. He would like to see research to determine “if the secretion from the pupae can also be useful in the transfer intestinal microbial communities that help ants digest food.”
This article is reproduced with permission and was first published on November 30 2022.