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Assessing Functional Group Contributions to Pathogen Outbreaks: Insights from Myrmica rubra

par Avanzi, Quentin ;Detrain, Claire
Référence Colloque UIEIS (31: 28 au 30 août 2023: Toulouse)
Publication Non publié, 2023-08-28

Communication à un colloque

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Résumé :

Ant colonies are at risk of disease outbreaks due to the density of genetically related workers living in a confined nest. To limit the impact of pathogens such as Beauveria bassiana, ants have developed a variety of collective behaviours grouped into a concept called ‘social immunity’. In this study, we have investigated how different functional groups respond to an urgent pathogen threat within the colony. Specifically, we tried to understand whether the discarding of contaminated items is carried out by a specific functional group or by workers from any group that specialise in the short term. We also analysed how the pathogen exposure can alter the survival of different functional groups. By tagging ants and following Myrmica rubra workers individually for three days, we were able to establish an accurate behavioural profile for half the colony members. We then exposed the colony to uninfected and infected cadavers and followed individual responses to the threat. Intermittent foragers were more involved in necrophoresis than any other functional group, as they touched, moved, and discarded more corpses. Domestic workers also contributed significantly to the rejection of infected corpses. Foragers and Inactive ants were the less committed in corpses discarding, respectively due to their spatial position outside the nest and their higher response threshold. Nurses, to a lesser extent, were also involved in the management of fungus infected cadavers, which is surprising considering their primary role in brood care. These findings raise questions about the trade-off between having a small number of highly specialised workers or many nestmates who can perform the collective task more quickly in the context of sanitary care. We explain this discrepancy between 'specialisation' for uncontaminated corpses and 'speed' for contaminated ones to an overall lower response threshold for infected bodies. Finally, the individuals engaged in necrophoresis were the ones that most performed prophylactic grooming suggesting the existence of hygienist workers inside the ant colony.