Developing termite turrets with no blueprint

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PICTURE: The interior of a termite nest shows complex, interconnected floors and ramps. view More

Photo Credit: (Courtesy Guy Theraulaz / Harvard SEAS)

After a series of studies of the physiology and morphogenesis of termite mounds over the past decade, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have now developed a mathematical model to explain how termites construct their intricate mounds.

The research is published in the Proceedings of the National Academy of Sciences.

“Termite mounds are among the greatest examples of animal architecture on our planet,” said L. Mahadevan, professor of applied mathematics, organismic and evolutionary biology and physics and lead author of the study at Lola England de Valpine. “What are they for? How do they work? How are they built? These questions have puzzled many scientists for a long time.”

In previous research, Mahadevan and his team have shown that day-to-night temperature fluctuations encourage convective flow in the mound, which not only aerates the colony but also moves pheromone-like cues that trigger building behavior in termites.

Here the team zoomed in further to understand how termites build the closely interconnected soils in individual mounds without a plan or planner. With experimenters from the University of Toulouse, France, led by Guy Theraulaz, the researchers mapped the internal structures of two nests using CT scans and quantified the distance and arrangement of floors and ramps. Adding to the complexity of the nests is the fact that termites not only build simple ramps to connect floors, but also spiral ramps, like the ramps in parking garages, to connect several floors.

Using these visualizations and incorporating previous insights into how factors such as daily temperature shifts and pheromone flows drive building, OEB PhD students Alexander Heyde and Mahadevan constructed a mathematical framework to explain the layout of the hill.

Heyde and Mahadevan viewed every component of the mound – the air, the mud, and the termites – as mixed fluids that differed in space and time.

“We can imagine the accumulation of hundreds of thousands of termites as a liquid that can perceive and act on their surroundings,” said Heyde. “Then you have a real fluid, air, that carries pheromones through that environment, which leads to new behaviors. Finally, you have mud that is moved by the termites and changes the way the pheromones flow. Our mathematical framework provided us with clear predictions for the distance between the layers and showed the spontaneous formation of linear and helical ramps. “

“Here is an example where we see the usual separation between the study of non-living matter and living matter breaking down,” Mahadevan said. “The insects create a microenvironment, a niche, in response to pheromone concentrations. This change in physical environment alters the flow of pheromones, changing the behavior of the termites and combining physics and biology with a dynamic architecture that is modulated and modulated by behavior.”

In addition to partially solving the mystery of how these mounds work and are built, research can well have implications for swarm intelligence in a number of other systems and even understand aspects of tissue morphogenesis.

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The research was written jointly by Lijie Guo and Christian Jost. It was supported in part by the U.S. and French National Science Foundation under grant numbers DGE-1144152, ANR-06-BYOS-0008, and PHY1606895.

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