Social Defences

Leaf-cutting ants returning to their colony.

Social defences

Ant societies have achieved formidable hygienic successes through sophisticated collective prophylaxis and social immune defences. We used leaf-cutting ants (Acromyrmex and Atta species) as model organisms to investigate innate immunity and behavioural defences in these social species.

Using a cross-fostering approach we addressed the influences of genotype and social rearing environment on both individual and social immune defences (Armitage et al. 2011), and we tested the influence of age and group living on innate immunity, in this case the phenoloxidase cascade (Armitage & Boomsma 2010). From a fitness perspective, we examined the trade-off between the immune system and queen ant sperm storage (Baer, Armitage & Boomsma 2006). In a collaboration with Hermogenes Fernández-Marín (INDICASAT, Panamá) and William Wcislo (Smithsonian Tropical Research Institute, Panamá) we examined the intriguing behaviour that the ants direct towards their brood: their mutualistic fungus has evolved a dual role – not only as a food source but is also actively used to cover their brood. We performed a phylogenetic study of this behaviour on 19 species (Armitage et al. 2012). Using parasitic fungal infections and behavioural assays we found that the mutualistic fungus may play a significant role in suppressing the spread of disease, thus adding a novel layer of protection to their defence portfolio (Armitage et al. 2016).