Parasites can mediate severe fitness costs and are thus important selective forces shaping the evolution of host phenotypes. Social insects are hosts for a diverse group of parasites, but their impact on the phenotypic traits of their social hosts is still poorly understood. Here, we tracked the survival of tapeworm-infected ant workers, their uninfected nestmates and of ants from unparasitized colonies. Our three-year study on the ant Temnothorax nylanderi, the intermediate host of the cestode Anomotaenia brevis, revealed a prolonged lifespan of infected workers compared to their healthy peers. Indeed, their survival rates resembled those of queens, whose lifespan can reach two decades. In contrast, uninfected workers suffered from increased mortality compared to workers from unparasitized colonies. Infected workers exhibit a metabolic rate and lipid content similar to young workers and they receive more social care than uninfected workers and queens. This increased attention could be mediated by their chemical profile, which we show to be more attractive. In conclusion, our study demonstrates an extreme lifespan extension in a social host following tapeworm infection. The long-lived infected ant workers exhibit many traits typical for young workers and future studies will tell how parasite infection alters the molecular regulation of aging.

Long-term survival data