title: A carbohydrate-rich diet increases social immunity in ants.
abstract: Increased potential for disease transmission among nest-mates means living in groups has inherent costs. This increased potential is predicted to select for disease resistance mechanisms that are enhanced by cooperative exchanges among group members, a phenomenon known as social immunity. One potential mediator of social immunity is diet nutritional balance because traits underlying immunity can require different nutritional mixtures. Here, we show how dietary protein-carbohydrate balance affects social immunity in ants. When challenged with a parasitic fungus Metarhizium anisopliae, workers reared on a high-carbohydrate diet survived approximately 2.8× longer in worker groups than in solitary conditions, whereas workers reared on an isocaloric, high-protein diet survived only approximately 1.3× longer in worker groups versus solitary conditions. Nutrition had little effect on social grooming, a potential mechanism for social immunity. However, experimentally blocking metapleural glands, which secrete antibiotics, completely eliminated effects of social grouping and nutrition on immunity, suggesting a causal role for secretion exchange. A carbohydrate-rich diet also reduced worker mortality rates when whole colonies were challenged with Metarhizium. These results provide a novel mechanism by which carbohydrate exploitation could contribute to the ecological dominance of ants and other social groups.
authors.affiliation: Department of Biology, University of St. Thomas, , St. Paul, MN, USA, School of Life Sciences, University of Sussex, , Brighton, UK, Graduate Program in EEB, Department of Zoology, University of Oklahoma, , Norman, OK, USA, Smithsonian Tropical Research Institute, , Balboa, Republic of Panama.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Kay
authors.forename: Abbie J
authors.initials: AJ
authors.lastname: Bruning
authors.forename: Andy
authors.initials: A
authors.lastname: van Alst
authors.forename: Tyler T
authors.initials: TT
authors.lastname: Abrahamson
authors.forename: W O H
authors.initials: WO
authors.lastname: Hughes
authors.forename: Michael
authors.initials: M
authors.lastname: Kaspari
mesh_terms: D000824:Animal Nutritional Physiological Phenomena / Q000276:immunology*; D000818:Animals; D001000:Ants / Q000276:immunology* / Q000502:physiology; D050260:Carbohydrate Metabolism / Q000276:immunology*; D060467:Disease Resistance / Q000276:immunology; D005247:Feeding Behavior; D006120:Grooming; D012919:Social Behavior
keywords: ants; disease resistance; ecoimmunology; geometric framework; nutrition; social behaviour