Harboring a parasitic tapeworm is usually not a desirable condition. But the life of an infected ant, known as Temnothorax nylanderi hits different.
Suppose an ant of this species, as a young larva, nibbles on the droppings of a woodpecker and contracts a tapeworm (Anomotaenia brevis). It could end up living three times longer than its peers, if not longer, and will rarely need to move a lower jaw.
Uninfected ants do the worker’s chores, carrying them around, feeding them, and caring for them for the rest of their days. These spoiled ants rarely leave the nest.
A research team led by entomologist Susanne Foitzik from the Johannes Gutenberg University in Germany has now found a possible explanation for this strangely idyllic lifestyle.
When a tapeworm takes up residence in an ant’s gut, it appears to do so pump antioxidants and other proteins into the creature’s bloodstream.
It’s still unclear what the health effects of these special proteins are, but there’s a real chance they might help infected ants stay young and tasty.
In the anomotenia In the life cycle of a tapeworm, an ant is not its final home. Reproduction in adulthood occurs inside a woodpecker’s body, meaning the parasite has a vested interest in keeping its transient host looking young, plump, and tasty. That way it could become a bird’s breakfast once it’s grown.
What happens to the ant colony is not the parasite’s concern as long as the infected ants survive until a woodpecker arrives.
In 2021, Foitzik and some of her other colleagues in Germany discovered this temnothorax Ants infected with tapeworms lived comfortably, the uninfected in a colony paying for the laziness of their fellow ants.
These worker ants, now busy tending to their infected brethren, died much, much sooner. And while neither the infected ants nor their vigilant handlers seemed to show any physiological signs of stress, the workers tended to their queens less lovingly while tending to the infected, which could spell trouble for the colony.
Because the infected ants looked so young, the researchers were still curious to find out what might help them live longer.
In their new study, which has yet to be peer-reviewed, the researchers again compared infected and uninfected ants, this time looking at the protein levels in the ants’ hemolymph (the equivalent of an invertebrate’s bloodstream).
They found that a tapeworm’s proteins make up a “significant fraction” of the proteins that flow through an individual’s hemolymph, and that two of the most abundant proteins were antioxidants.
A few other proteins could explain why infected ants are treated like royalty – although many of these were undetectable and there was no known equivalent in other organisms.
A protein called vitellogenin-like A, which is found in high levels in infected individuals, is not produced by the parasite but by the ant itself. It is known to regulate the division of labor and reproduction in ant communities.
Therefore, researchers hypothesize that this protein could influence ant behavior in a way that entices others to take an interest in them.
It is still unclear whether the tapeworm actively manipulates the gene expression of ant proteins such as vitellogenin-like A, or whether this is an accidental by-product of the parasitic infection.
“Since caste differences in social insects are usually not due to genetic differences but are controlled by differential gene expression, adopting pre-existing regulatory pathways that make an individual more queen-like could be an elegant strategy from the parasite’s perspective,” Foitzik and Colleagues point this out.
Still, it would be incredibly difficult, if not impossible, to prove that a parasite manipulates an ant’s body, rather than that an ant’s body responds to an intruder. The authors say that this potential manipulation route should be interpreted with caution.
The team in Germany plans to further study the parasite’s proteins to better understand how they might affect ant behavior, appearance and longevity.
The study was published on the preprint server bioRxiv before the peer review.