In a three-year study of parasitic infections by Anomotaenia brevis tapeworms in Temnothorax nylanderi ants, entomologist Susanne Foitzik and colleagues found something unexpected: rather than reducing its host’s fitness, as is typical of parasites, A. brevis greatly extends the lifespan of a T. nylanderi worker ant and seems to halt the effects of aging. Furthermore, those infected receive special treatment, ceasing their share of labor to sustain the colony and remaining in the nest as uninfected workers feed, groom, and transport them. By contrast, the researchers observed that uninfected workers in parasitized colonies have shortened lifespans, most likely because the ______blank