Trophallaxis: a charismatic quirk, simple food exchange, or an opportunity to conquer the world

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Adria LeBoeuf recently started her own research group at the University of Fribourg in Switzerland. She tries to understand how socially exchanged fluids evolve and how they can be co-opted by evolution to influence physiology and behavior. Here, Adria shares some information on trophallaxis in general, what, besides food, is exchanged with trophallaxis, and why you should join her lab.

A view compiled by Adria C. LeBoeuf

Charming images of ants kissing adorn classic texts like Forel’s Le Monde Social des Fourmis and many of the pop-science articles we find on the internet today. Why? Ants engaging in this mouth-to-mouth fluid exchange are not only adorable but they also remind us of the importance of cooperation and sharing. Individual ants passing fluid from one individual to another – the ant equivalent of breaking bread!

Despite this classic image, not all species of ants engage in trophallaxis. Generally, ants that don’t eat liquid food don’t tend to show this behaviour. Why bother chewing, processing and storing liquid cricket when you can carry solid cricket back home to the nest more quickly? On the other extreme, ant species that tend sugary-liquid-secreting aphids or plants routinely engage in trophallaxis. Many such ant species, most typically Formicines, engage in this behaviour all the time, so much so, that they essentially build a social circulatory system connecting all individuals in the colony.

Camponotus workers performing trophallaxis. (© Adria LeBoeuf)

While smooth flow in a distribution network is great for any cooperative group (think of the postal service or your local public transit system), some species seem to have harnessed this trophallactic distribution network for more than just food transfer, possibly resulting in… world domination. How is this possible? One key factor here is that trophallaxis doesn’t occur just between adults in a colony – in many species, larvae are fed by adults via trophallaxis. This means that the colony can collectively spike the baby bottle with hormones, growth factors and immune components to alter the growth and development of the next generation. Indeed, in some of the most prolific trophallaxers out there, Camponotus, the trophallactic fluid is full of hormones, growth factors and immune components along with typical digestive proteins. Furthermore, components transmitted by trophallaxis can, in turn, influence larval development (LeBoeuf et al. 2016, 2018). One of these hormone-regulator genes, juvenile hormone esterase, underwent a form of neofunctionalization – shifting from its classic within-individual role in insect development to an across-individual role regulating development over the social circulatory system. Taking our Camponotus as an example, we see that their evolution of developmental regulators transferred over a social circulatory system provides them with a stunningly direct means of control, presumably allowing them to adapt the colony’s maturation to its environmental conditions. Camponotus is one of the most species-rich genera of all ants present all over the world in extremely diverse ecosystems. Was their social circulatory system key to world domination? Perhaps.

Adria in the lab. (© Adria LeBoeuf)

Get involved

The LeBoeuf lab at the University of Fribourg in Switzerland just got started this year. If you want to join us on our quest to understand trophallaxis and the social circulatory system, get in touch!

More generally, one of the biggest issues holding back our understanding of trophallaxis and the social circulatory system in ants is that we don’t know which species do trophallaxis and which don’t! Help us by telling us if you see trophallaxis in your favourite species: 

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