The presence of conifer resin decreases the use of the immune system in wood ants

Abstract

1. Wood ants (Formica paralugubris) incorporate large amounts of solidified conifer resin into their nest, which reduces the density of many bacteria and fungi and protects the ants against some detrimental microorganisms. By inducing an environment unfavourable to pathogens, the presence of resin may allow workers to reduce the use of their immune system. 2. The present study tested the hypothesis that the presence of resin decreases the immune activity of wood ants. Specifically, three components of the humoral immune defences of workers kept in resin-rich and resin-free experimental nests (antibacterial, lytic, and prophenoloxidase activities) were compared. 3. The presence of resin was associated with reduced bacterial and fungal densities in nest material and with a small decrease in worker antibacterial and lytic activities. The prophenoloxidase activity was very low in all workers and was not affected by the presence of resin. 4. These results suggest that collective medication with resin reduces pathogen pressure, which in turn decreases the use of the inducible part of the immune system. More generally, the use of plant secondary compounds might be an efficient and economical way to fight pathogens.

Genetic variation in resistance, but not tolerance, to a protozoan parasite in the monarch butterfly

“…For instance, the current study shows that monarchs possess both qualitative and quantitative resistance, and a recent study has also shown that monarchs have a behavioural defence mechanism through which they can preferentially lay their eggs on anti-parasitic host plants (T. Lefèvre, L. Oliver, M. D. Hunter & J. C. de Roode 2009, unpublished results). It is often suggested that organisms need not invest in multiple defence mechanisms at once [21,71,72], and a recent review has suggested that free-moving (as opposed to sessile) organisms may invest more heavily in defence mechanisms other than tolerance [29]. The reason for this is that sessile organisms cannot move away from parasite threats and are more dependent on dealing with unavoidable damage.…”

Pathogen-associated self-medication behavior in the honeybee Apis mellifera

“…However, by measuring immune response, the prophenoloxidase activity (part of the humoral innate immune response of insects) was very low and not affected by the presence of resin. Additionally, only a light decrease in antibacterial and lytic activities was observed (Castella et al 2008).…”

Propolis and bee health: the natural history and significance of resin use by honey bees

“…The results of this study support those of previous laboratory studies on another social insect, the wood ant Formica paralugubris, which collects and distributes resin from spruce trees throughout its nest material. Soil collected from ant nests experimentally enriched with this resin had significantly fewer pathogenic bacteria and fungi (Christe et al, 2003), and adult ants in colonies experimentally made resin-rich did not invest as much in individual immunity (indicated by decreased antibacterial ability of the hemolymph) compared to ants in resin-deprived colonies (Castella et al, 2008a), which resulted in increased survival during a pathogen challenge (Chapuisat et al, 2007). Therefore, as with F. paralugubris ants, it is likely the presence of propolis in a honey bee colony may reduce the investment in the innate immune response by acting as an external immune defense mechanism.…”