Ant queens turn to cannibalism for controlling disease in their colonies

You know those ants you see scuttling around your garden? Have you ever thought about how they look when they are sick?

A research team led by the University of Oxford has unveiled a startling discovery about these industrious insects. Queen ants, instead of nursing their sick young, opt for a rather grim alternative.

The moment they notice an offspring showing signs of illness, they chow down on them. Yes, they eat their ailing larvae, transforming them into energy to produce new eggs.

Cannibalism for ant colony survival

But why such a seemingly harsh measure? Well, ant queens are typically lone wolves when it comes to setting up new colonies.

During these early stages, the brood is extremely prone to diseases, posing a serious threat to the colony’s survival.

To combat this, the queen puts on her chef’s hat and whips up a meal out of the sick larvae before they become infectious.

Presenting ant queens with sick larvae

How was this discovered? Well, Oxford‘s Department of Biology presented the queens of the black garden ant with larvae infected with a lethal fungal pathogen.

The infection was deadly, but not yet contagious when the queens were introduced. And then, what a feast it was. The queens devoured 92% of the uninfected larvae, leaving no trace behind.

“We observed the queens get to work immediately as they find a sick larva in their pile. They spend several hours making sure every piece is consumed,” noted Dr. Chris Pull, the lead researcher and a member of Oxford’s Department of Biology.

How do the queens avoid illness?

Interestingly, all queens survived the feast despite the potential risk of contagion.

The scientists believe that the queens shield themselves by swallowing an antimicrobial venom that they produce in a unique gland at their abdomen’s tail end.

Some queen ants were even witnessed massaging this gland during their mealting sessions.

Cannibalism gives ants a reproductive boost

And that’s not all, the queens who consumed their infected larvae saw a 55% hike in their egg production compared to their non-cannibalizing counterparts.

This suggests that the ingested offspring’s nutrients are recycled for reproduction – a process we could term, quite appropriately, ‘recycling life.’

“The queens start their colonies alone, sacrificing a lot of their own sustenance to raise their first batch of workers. The queens who churn out the most workers stand a greater chance at survival,” explained study co-author Flynn Bizzell.

“By eating and recycling infected larvae into brood production, invaluable resources are not lost.”

Ants control disease through cannibalism

Interestingly, the queens did not consume larvae that had reached the infectious stage. Instead, they sprayed the larvae with their antimicrobial venom, seemingly attempting to control the infection.

However, the majority (80%) contracted the disease and later died, emphasizing the importance of nipping the problem in the bud.

The ability of ant queens to selectively consume larvae before they become infectious and to utilize antimicrobial venom as a line of defense highlights a sophisticated evolutionary strategy for disease management.

This dual approach ensures that resources are not wasted on doomed individuals while simultaneously fortifying the remaining larvae against threats.

Maintaining the health of the colony

The venom, believed to contain potent antimicrobial compounds, plays a critical role in maintaining the health of the colony at its most vulnerable stage.

By employing this venom to spray infected larvae, queens attempt to curb disease spread and protect their investment in future generations.

The chemical composition of this venom is now a subject of rigorous inquiry, as it may offer insights into developing new biocontrol agents and therapeutic compounds in broader biological applications.

Optimal use of limited resources

This intriguing cannibalism behavior unveils the complex calculus of reproductive strategy in ants, where every action is directed towards maximizing the colony’s success.

The queens’ decision to consume their sick offspring not only enhances their immediate reproductive output but also secures the long-term viability of the colony.

By effectively ‘recycling’ the nutrients, queens ensure the optimal use of limited resources, particularly during the crucial phase of colony establishment.

Viewing this behavior through an evolutionary lens, it becomes clear that such extreme measures are the products of natural selection, fine-tuned over millennia to increase the likelihood of survival in harsh environments.

“Hygienic cannibalism” of ants

The survival strategy of ant queens, known as “hygienic cannibalism,” has only been witnessed among queens and never among mature worker ants.

Unlike queens that seal themselves into the nest, worker ants can dispose of infected larvae by carrying them out of the nest.

Ant queens, on the other hand, have found a way to turn a potential disaster into a means of long-term survival using cannibalism.

“Our findings show that cannibalism addresses disease containment and corpse disposal in the queens’ underground bunker while ensuring valuable nutrients are not wasted,” said Dr. Pull. “This significantly improves their odds of successfully establishing a colony.”

The study is published in the journal Current Biology.

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