Centre National de la Recherche Scientifique

The queens in colonies of social insects, such as ants, bees, and wasps, are considered the veritable embodiment of specialization in the animal kingdom. The common perception is that the queen's only task is to lay eggs -- and that this attribute is an inherent trait, not influenced by external factors. In contrast, recent research has demonstrated that in certain ant colonies the social environment can play a crucial role in shaping the behavioral specialization of the queens. The queens in colonies of social insects, such as ants, bees, and wasps, are considered the veritable embodiment of specialization in the animal kingdom. The common perception is that the queen's only task is to lay eggs -- and that this attribute is an inherent trait, not influenced by external factors. In contrast, recent research undertaken at Johannes Gutenberg University Mainz (JGU) has demonstrated that in certain ant colonies the social environment can play a crucial role in shaping the behavioral specialization of the queens. "With regard to the ant species we studied, it is social factors that control whether queens become specialized or not. Our findings challenge the widely accepted notion of social insect queens as inherently specialized egg-laying machines," stated Dr. Romain Libbrecht. The research was conducted by the Reproduction, Nutrition, and Behavior in Insect Societies group at JGU under the supervision of Dr. Romain Libbrecht, an evolutionary biologist. The corresponding paper has recently been published in Functional Ecology. Dr. Romain Libbrecht currently works at the Centre National de la Recherche Scientifique (CNRS) in the Insect Biology Research Institute of the University of Tours. Concept of insect societies as superorganisms consisting of specialized individuals It is generally assumed that social insect colonies consist of queens that monopolize reproduction and sterile workers responsible for all non-reproduction-related tasks, such as the care of the brood, i.e., eggs and larvae. Libbrecht's team now questioned this basic assumption. They focused on ant species where the queens found new colonies alone and without the help of workers. "Interestingly, these founding queens are not yet specialized in terms of their behavior at this stage of their lives," Libbrecht pointed out. "They themselves assume all tasks in the nest, such as brood care, to ensure successful production of the first generation of workers." In their experiments, Libbrecht's group studied the black garden ant Lasius niger that is native to Germany. They found the social environment to be a core factor in determining the behavioral specialization of founding queens. "The introduction of workers in the nests of founding queens suppressed the natural predisposition of the queens to look after their brood themselves. And, conversely, when we isolated queens specialized in egg-laying from their workers, they rapidly reverted to the brood care behavior observed in the case of founding queens, even after many years of specialization." Revision of the accepted view of the division of labor in insect societies Libbrecht emphasized that the behavior observed during the study challenges the traditional view of social insect queens as being intrinsically specialized in egg production. Instead, the findings demonstrate that the presence of workers not only triggers the egg-laying specialization of queens but also actively maintains it in established colonies. The discovery of such social control of queen specialization may reshape our understanding of the functioning of insect societies and their division of labor. Romain Libbrecht was head of the Reproduction, Nutrition, and Behavior in Insect Societies group at the Institute of Organismic and Molecular Evolution (IOME) at Johannes Gutenberg University Mainz from 2016 to 2022. Since 2023, he has been a researcher at the Insect Biology Research Institute at the CNRS of the University of Tours. He is particularly interested in examining how organisms adjust their reproduction, physiology, and behavior in response to environmental conditions.

Physicists show how patterns can emerge from chaos in turbulent fluids. The turbulent motion of a tumbling river or the outflow from a jet engine is chaotic: that is, it contains no obvious pattern. But according to a new study, regular patterns can emerge from the turbulent motion of fluids. What you need is an intriguing property called "odd viscosity" that arises under certain conditions, such as when the particles in the fluid all spin in the same direction. Though it's a specialized circumstance, there are many contexts in nature where a version of this effect may exist, such as in the corona of the sun and the solar wind. "This surprising effect may add to the growing toolbox to control and shape turbulence," said Michel Fruchart, formerly a postdoctoral researcher at UChicago, now faculty at the French Centre National de la Recherche Scientifique (CNRS) and co-first author of the paper describing the findings. The study, a collaboration between the University of Chicago, Eindhoven University of Technology in the Netherlands, and CNRS, is published March 20 in Nature. A chaotic nature Despite how much we've learned about classical physics in the past centuries, there's one problem that still resists full explanation: the phenomenon known as turbulence. Though turbulence appears every day around us -- from the clouds churning in the atmosphere overhead to the very blood flowing through our vessels -- it is still not as well understood as other common physical phenomena. "Turbulence might be commonplace in nature, but it is still only partially understood," said Xander de Wit, co-first author of the publication and a Ph.D student with Eindhoven University of Technology. This is despite the fact that if we could understand and control turbulence, we might be able to achieve many breakthroughs; perhaps we could design more efficient airplane wings, engines, and wind turbines, for example. However, there are things scientists do know about turbulence. If you shake a bottle of water, you'll see eddies forming. They start out at roughly the size of the length of the bottle; then the eddies split into smaller eddies, and then again into smaller eddies, and so on until the eddies dissipate. This is known as a cascade. But if you do the same thing but confine the water to a thin layer, the eddies will instead merge to form one big vortex -- the Great Red Spot on Jupiter's surface is an example of this phenomenon, said Fruchart. The group of scientists wondered if it was possible to make, and hold, medium-size eddies -- neither one big eddy, nor smaller and smaller ones. The answer is yes -- if your fluid has is displaying a property known by the term "odd viscosity." Viscosity usually means a measurement of how hard it is to stir -- for example, it's harder to stir a jar of honey versus a jar of water. In normal viscosity, the movement dissipates the energy you've injected to it by stirring with your spoon. But "odd viscosity" changes the way objects move but doesn't dissipate energy. It's been seen in certain rare conditions in the laboratory. The researchers built a simulation where the particles displayed 'odd viscosity,' -- in this case, by making all of the particles of the fluid spin like tops. Then, by tweaking the parameters, such as how fast the particles spin, the researchers found a surprise. At a particular point, they began to see patterns instead of random eddies. "The trick, we found, is to create a mixed cascade, where large eddies tend to split and small eddies tend to merge," said Fruchart. "If you get the balance just right, you see patterns form." "When we first saw these effects, we didn't fully understand what we were looking at, but you could tell there was something different even to the unaided eye," said study co-author and UChicago Ph.D student Tali Khain. "We had to develop a theory to explain it, and that was really exciting." Though not all particles in fluids spin like tops, there are examples in nature. For example, electrons or polyatomic gases in a magnetic field do behave this way. "In addition to the sun and solar wind, there are diverse contexts where a version of this effect may exist, including atmospheric flows, plasmas and active matter," said UChicago Prof. Vincenzo Vitelli, one of the senior authors on the paper. As the scientists work to develop a fuller understanding of their findings, they hope it will lead to a better understanding of the interplay between eddies and waves in turbulent flows. "We are only at the beginning," Vitelli said, "but I am fascinated by the idea that you can take a turbulent state that is the epitome of chaos, and use it to make patterns -- that is a profound change made by just a twist on the smallest scale."

Tiny particles such as ice crystals or ash particles tend to oscillate as they settle through the atmosphere. In their experiments, the scientists were able to track non-spherical particles of size smaller than 1 millimeter with unprecedented accuracy. Their observations gave rise to a model which can help to refine prediction on air pollutants or weather forecasts. Tiny particles such as ice crystals or ash particles tend to oscillate as they settle through the atmosphere. In their experiments, the scientists were able to track non-spherical particles of size smaller than 1 millimeter with unprecedented accuracy. Their observations gave rise to a model which can help to refine prediction on air pollutants or weather forecasts. The atmosphere contains many tiny solid particles. Scientists from the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) and the University of Göttingen in collaboration with the Centre national de la recherche scientifique (CNRS) in France and the university of Gothenburg, Sweden, now studied how such non-spherical particles settle in air. For this, they used a new precision apparatus equipped with high-speed cameras and a novel particle injection mechanism. Using a 3D-printer, they created particles of different shapes resembling discs of thickness as low as 50 micrometer and rods of length as high as 880 micrometers. Thanks to this setup, they could observe that particles tend to oscillate as they settle in quiescent air. "So far, most studies on the behavior of such small particles were done with models in liquids since experiments in air are extremely challenging," Mohsen Bagheri, group leader at MPI-DS, describes previous approaches. "However, the true settling dynamics could not be explored this way. They were now revealed in our experimental setting, directly measuring the motion of real-size particles, which are much heavier than the surrounding environment," he continues. The observed oscillation could impact the collision of individual particles, their travelling distance in the atmosphere and their interaction with the solar radiation. Predicting the dynamics of particles Typically, atmospheric particles are not perfectly spherical, but rather flattened or elongated structures. The scientists developed and tested a model to describe and predict the movement of such particles, which very accurately captures the experimental results. The new model can be used to study the dynamics and formation of particles clusters and the resulting effects in everyday life. "In particular, our results can help to better predict how long pollutants reside in the atmosphere or how precipitation is initiated in clouds," summarizes Alain Pumir. The CNRS researcher developed the model together with his colleagues Bernhard Mehlig and Kristian Gustavsson. In total, these new insights contribute to a more accurate understanding of atmospheric particles, and how they affect our environment and climate.