International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Timing of individual and colony level disease defences in ants

Author(s):
Stephen Nilsson-Møller, Stephen Nilsson-Møller , Michael Thomas-Poulsen , Line Vej Ugelvig
Institution(s):
Detpartment of Biology, Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark; Detpartment of Biology, Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark ; Detpartment of Biology, Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark ; Detpartment of Biology, Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark
In ants and other social insects, defences towards incoming infectious microbes act at both the individual and the colony level. In either case, rapid detection and effective responses are crucial for success. Here we investigate the timing of individual and colony level disease defences in the leafcutter ant Acromyrmex echinatior towards the fungal pathogen Metarhizium robertsii. At the individual level, the infection process of M. robertsii includes a pre-infection stage, where its conidiospores germinate and grow on the ant cuticle. Within 1-2 days, it forms a structure that enables penetration of the ant cuticle, at which point an internal, local infection can establish. Unless the ant rapidly mounts an effective immune response, the fungus will spread through the entire ant body, destroying vital organs and ultimately killing the ant. We study immune gene expressions of individual ants to uncover whether recognition, signalling and effector molecules are up-regulated before, or only when, an internal fungal infection takes place. The immune gene expression will be correlated with fungal presence and abundance in specific tissues. At the collective level, nestmates can through sanitary care behaviours, including the use of antimicrobial substances, greatly reduce the number and viability of conidiospores on the cuticle of contaminated individuals, thereby enhancing individual and collective survival. However, this requires detection of and sanitary care towards contaminated individuals early in the pre-infection phase. We experimentally manipulate the olfactory ability of nestmates to investigate its role in regulating the onset of colony-level disease defences. This allows us to determine how a delayed response affects the survival of the contaminated individual.
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