Losing flight had huge benefits for ants, finds new study

October 18, 2020

Ants are one of the most successful groups of animals on the planet, occupying anywhere from temperate soil to tropical rainforests, desert dunes and kitchen counters. They're social insects and their team-working abilities have long since been identified as one of the key factors leading to their success. Ants are famously able to lift or drag objects many times their own weight and transport these objects back to their colony. But with previous research having focused on the social aspects of an ant colony, looking at an individual ant has been somewhat neglected.

Now, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) and Sorbonne University in Paris have investigated why individual worker ants are so strong by taking X-ray images and creating 3D models of their thorax - the central unit of their bodies - to analyze their muscles and internal skeleton. Their study, published in Frontiers in Zoology, examines the hypothesis that loss of flight in worker ants is directly connected to the evolution of greater strength.

"Worker ants evolved from flying insects," said Professor Evan Economo, who leads OIST's
Being able to fly might be a common dream amongst people but the reality of flight is that it puts strong constraints on the build of a body. In flying insects, the wing muscles occupy a major part of the thorax - sometimes more than 50%. This means that other muscles, which are used to support and move the head, legs, and abdomen are constrained and squeezed up against the exoskeleton.

But once the constraints of flight are removed, all that space in the thorax is open, which, the researchers surmised, would allow the remaining muscles to expand and reorganize.

Previous research in this area had focused on the external structure of ants but, with the technology available at OIST, the researchers were able to gain a highly detailed picture of what was going on inside the thorax. The aim was to analyze the general features common across all ants, rather than focus on the specialization of certain species. To do this, the researchers did a detailed analysis of two distantly related ant species, including both the wingless workers and the flying queens, and confirmed their findings across a broader sample of species.

They used advanced X-ray technology to scan the internal and external anatomy, like CT scans used in a hospital, but at much higher resolution. From these scans, the researchers mapped all the different muscles and modeled them in 3D. The result was a comprehensive image of the inside of the thorax. They then compared findings from these two species to a range of other ants and wingless insects.

As predicted, the researchers found that loss of flight had allowed for clear-cut reorganization of the thorax. "Within the worker ant's thorax, everything is integrated beautifully in a tiny space," said the late Dr. Christian Peeters, lead author of this paper, who was a research professor at Sorbonne University. "The three muscle groups have all expanded in volume, giving the worker ants more strength and power. There has also been a change in the geometry of the neck muscles, which support and move the head. And the internal attachment of muscles has been modified."

Interestingly, when looking at wingless wasps, the researchers found that these insects had responded to the loss of flight in a completely different way. Wingless wasps are solitary and consume food as they find it. On the other hand, ants are part of a colony. They hunt or scavenge for food that then needs to be carried back to the nest for the queen and younger nestmates, so it makes sense that there was a selection pressure to promote carrying ability.

Ants have been studied for centuries in terms of their behavior, ecology, and genetics but, the researchers emphasized, this story of strength has, so far, been somewhat overlooked. The next step is to develop more detailed biomechanical models of how different muscle groups function, do similar research on the mandible and legs, and explore the diversity seen between ant species.

"We're interested in what makes an ant an ant and understanding the key innovations behind their success" explained Professor Economo. "We know that one factor is the social structure, but this individual strength is another essential factor."
Alongside Professor Economo and Dr. Peeters, the research group included Dr. Roberto A. Keller from University of Lisbon and OIST, Mr. Adam Khalife from Sorbonne University and OIST, Dr. Georg Fischer and Mr. Julian Katzke from OIST, and Dr. Alexander Blanke from University of Cologne.

Watch an animation about this work here:

Dr. Christian Peeters

Dr. Christian Peeters passed away in early September 2020, just before this paper was published. In his scientific career, which spanned over thirty-five years and took him around the world, Dr. Peeters researched social insect societies with a focus on the evolution of ant reproductive behaviors, colony strategies, and morphological adaptations. In addition to publishing a long list of scientific papers, Dr. Peeters regularly created videos, gave talks, and contributed to online resources to make his research accessible to a non-scientific audience. OIST recognizes Dr. Peeters significant contributions to science, his passion for entomology, and the work he did in collaboration with the Biodiversity and Biocomplexity Unit.

Okinawa Institute of Science and Technology (OIST) Graduate University

Related Evolution Articles from Brightsurf:

Seeing evolution happening before your eyes
Researchers from the European Molecular Biology Laboratory in Heidelberg established an automated pipeline to create mutations in genomic enhancers that let them watch evolution unfold before their eyes.

A timeline on the evolution of reptiles
A statistical analysis of that vast database is helping scientists better understand the evolution of these cold-blooded vertebrates by contradicting a widely held theory that major transitions in evolution always happened in big, quick (geologically speaking) bursts, triggered by major environmental shifts.

Looking at evolution's genealogy from home
Evolution leaves its traces in particular in genomes. A team headed by Dr.

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.

A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.

Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?

Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Read More: Evolution News and Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.