Arianna Schneier writes about the longevity-altering effects of a tapeworm that infects ants.
A three-year study revealed that tapeworm-infected, compared to uninfected, worker ants exhibited increased lifespans similar to that of queen ants. The study, conducted by Susanne Foitzik from Johannes Gutenberg University with various collaborators, focused on Temnothorax nylanderi found in Central Europe. The worker ants of this species are infected with a tapeworm, Anomontaenia brevis, and act as its intermediate host. These parasites in the larval stage of their life cycle live in the ants’ body fluid known as haemolymph. This discovery is quite unexpected because parasites are usually thought to have a detrimental effect on their hosts. Thus, this parasite having a beneficial effect on the host ant, such as an increased lifespan, is quite unexpected. Additionally, overall observation of the colonies does not reveal any strong consequences of infection on the colony. It is also theorised that the increased lifespan of the intermediate host, T. nylanderi, assists with transmission into the woodpecker where it completes its life cycle.
Ants are eusocial insects meaning that they live together and cooperate by dividing tasks between different groups. The specific task group an ant is part of corresponds to the ant’s lifespan. For example, the queen is responsible for reproduction and is the most long-lived, some queens live up to two decades. This long lifespan makes sense as the queen is confined to the nest, and thus is generally safe and cared for by nurse ants. Meanwhile, the female workers exhibit a much shorter lifespan, usually from weeks to months. The tasks of the worker ants are further subdivided, with the younger workers, also known as nurses, tending to work in the nest. While the older workers are responsible for the search for food outside the nest, a much riskier task. Thus, the workers create a safe and caring environment in the nest, which is likely responsible for the extended lifespan of the queen.
Interestingly, analysis of the infected ants revealed that they share similarities, such as metabolic rate and other molecular contents, with the younger ants (e.g. similar hydrocarbon composition of the cuticle). As the tapeworm takes nutrients from the host, this may be why the infected ant’s body mass and fat content are lowered, and become similar to that of regular young ants. The infected ants are also more commonly found inside the nest, like the younger ants, thus protecting them from the dangers of scavenging. Studying the behaviour of the ants revealed that the infected ants receive as much, sometimes more care than the queen. Perhaps the same benefits that the queen reaps, such as social care and staying in the nest, provides a possible explanation for the extended age of the infected ants.
Furthermore, chemical signals from the infected ant’s cuticle are potentially responsible for the increased attention from other ants. However, more research is needed to determine the exact role these signals contribute to the increased lifespan of these ants.
The forces underlying the relationship between longevity and social standing in eusocial insects are still largely unknown. However, this study on a Central European ant species, T. nylanderi, has undoubtedly contributed to new insight into this relationship in eusocial insects.
Written by Arianna Schneier, a final year Molecular Biology student, and edited by Diana Jorge.