In certain ant species, there are ants that somehow manage to defy the passage of time. Not only do they survive for years, while their genetically identical sisters die off in a matter of months, they also emanate youthful pheromones that give them unmatched status among the workers. With a persistent tawny hue that is only found in young ants, they have life on easy mode, being constantly showered with gifts and attention. Their secret? Tapeworms.
This type of symbiotic yet still parasitic relationship is fairly rare and is sometimes observed between microbes and other insects such as mosquitoes, beetles, and wasps. However, the case of the infected Temnothorax ants is a bit more extreme than any of the relationships that have been observed in the past. When infected with a tapeworm, these ants can live for at least three times longer than other members of the colony, with the upper range of longevity being undetermined as of yet. However, some researchers believe that it can be more than a decade, even up to 20 years.
What’s even more interesting is that outside of this relationship with the tapeworm, the Temnothorax ant is really mundane. The colony structure is traditional, with one queen that is tended to by the workers. However, as soon as a worker ingests bird feces that are infested with tapeworm eggs, all normalcy goes out the window. The parasite will hatch inside the ant’s abdomen, where it will absorb a ton of nutrients that will help it survive. In exchange, the tapeworm will give the ant a freakishly long life.
As part of the study, researchers looked at a Temnothorax ant colony for three years in order to compare the fate of infested and non-infested workers. Unsurprisingly, most of the original workers that were not infested died during that time span. However, over half of the workers that had the parasite not only survived, but were still apparently young. They were also treated like royalty, engaging in very little work. They enjoyed being groomed, carried and fed by other members of the colony, to the point where they were often better treated than the queen of the colony.
So why is this a parasitic and not a symbiotic relationship? What are the downsides? Well, the effect was felt by the rest of the colony. In order to take care of the infested ants, the workers had to work harder, causing them to die sooner. Being that ants are social insects, the cost of parasitism is paid by the colony itself. On top of that, infected ants lose many of their ant-like traits, including the need to avoid being eaten by birds. Since this particular species of tapeworm does not produce eggs until the ant is consumed by a bird, it has to transform its ant host into easy prey and it has to ensure that the host survives for as long as needed in order for it to reproduce.