In the natural world, parasitism occurs quite frequently with a variety of outcomes, often negatively affecting the quality of life. In contrast, parasitism by A. brevis in worker ants of Temnothorax nylanderi results in a lifespan at least 3 times longer than that of uninfected workers, and potentially extending to equal that of a queen. While most parasites do not cause acute or catastrophic detriment to their host, often there is an observable impairment to either lifespan or fitness. Beros et al. note that occasionally there are instances in such host-parasite systems whereby lifespan extension is imparted to the host; however, these benefits come at the cost of reduced reproductive health. Curiously, their recent studies not only characterize a parasitic relationship that provides the benefit of a robust lifespan, but one in which there seems to be no trade-off in reproductive fitness. These parasitized workers actually seem to have increased reproductive potential when compared to other fertile, yet not actively breeding, members of the colony known as nurses.
In an attempt to determine a mechanism for this phenomenon, researchers measured a variety of metabolic, physiological, and social characteristics exhibited by infected and uninfected ants. According to their observations, physiological changes to infected workers result in a phenotype more characteristic of colony members belonging to the nurse caste, including similar metabolic rates, body mass, and lipid content. Additionally, infected workers have a changed cuticular hydrocarbon profile (chemical secretions similar to pheromones) seemingly resulting in greater social caretaking being afforded to them, which again is similar to their nurse-caste colony-mates.
Although infected workers appear most similar to nurses, there may be other factors at play as nurses do not exhibit lifespans similar to queens. Previous studies by the authors have observed changes in gene expression brought about by this particular host-parasite system. These changes could represent potential novel targets of future studies and lead to insights into areas of the aging process that are as yet unexplored.
Unraveling the mechanism by which a parasite extremely alters ant lifespans could be informative to potentially extending the human lifespan.