Data from: Ant societies buffer individual-level effects of parasite infections

Parasites decrease host fitness and can induce changes in host behavior,
morphology, and physiology. When parasites exploit social insects, they
influence not only infected individuals but the society as a whole.
Workers of the ant Temnothorax nylanderi are an intermediate host for the
cestode Anomotaenia brevis. We studied a heavily parasitized population
and found that while parasite infection had strong and diverse
consequences for individual workers, colony fitness remained unchanged. On
the individual level, we uncovered differences among the three worker
types: infected and healthy workers from parasitized colonies and healthy
workers from non-parasitized colonies. Infected workers were smaller than
healthy ones and had, as parasite load increased, smaller heads.
Behavioral changes extended to all workers from parasitized colonies,
which were less active but groomed more. Healthy workers from parasitized
colonies showed behavioral patterns intermediate to those of infected
workers and healthy workers from non-parasitized colonies. Despite the
lower activity level, an important fitness parameter - per-worker
productivity - remained unaltered in parasitized colonies. However, the
investment strategies of parasitized colonies changed as their sex ratio
became male-biased and male body size increased. In short, ant colonies
can buffer the drain of resources by the parasite despite strong effects
on individual workers.