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Nature seems to offer you the escapism of urban life, but the world under you may tell a different story. Even in the shade of fruit trees, you could be surrounded by small skyscrapers – not steel or concrete, but microscopic worms wiggle and wrapped in the shape of a long vertical tower.
These miniature architects, known as nematodes, are found all over the Earth’s surface, but German scientists recently witnessed their impressive architectural techniques in nature for the first time.
A few months after carefully inspecting rotten pears and apples in local orchards, researchers from the Max Planck Institute for Animal Behavior and the University of Constance found that worms 1 millimeter long (0.04 inches) were able to climb each other and accumulate structures up to ten times their individual sizes.
For more information on the mystical physics of the soft, slimy tower, the researchers brought samples of nematodes called caenorhabditis elegans into the laboratory and analyzed them. There, scientists realized that worms could be assembled in a few hours. Some people detected the environment, searched for buildings accordingly, and reached out from the twisted chunks as “arms” to explore the buildings. However, it was not immediately clear why the worm formed the structure.
The team’s findings published Thursday in the Journal Current Biology show that even the smallest animals can encourage big questions about the evolutionary purpose of social behavior.
“What we got was more than a worm standing above each other,” said Senior Research Author Serena Din, who is the leader of the largest Planck research group in genes and behavior. “It’s a coordinated super-body, acting as a whole and moving.”
To find what motivates the nematode building’s behavior, the research team tested the worm’s response to being thrust, protruding, and even visiting by fly while stacked in tower formation.
“We found that they were very responsive to the presence of stimuli,” said Daniela Perez, the first author of the study. “They feel it, and then the tower goes towards this stimulus, and our metal picks and flies become lively.”
This coordinated response suggests that hungry nematodes can come together and ride large animals such as insects and easily frown to transport them to green pastures (not) to eat more rotten fruits.
“When you think about it, an animal 1mm long cannot craze all the way to the next fruit two meters (6.6 feet) apart. It could easily die along the way or be eaten by a predator,” Perez explained. She added that nematodes can hitchhike solos too, but once they arrive in a new area within the group, they may be able to continue recreating.
The structure itself could also serve as a mode of transport, Perez noted, as evidenced by the way some worms form bridges throughout the gap in the Petri dish, reaching from one surface to another.
“The discovery is really exciting,” said Oritt Pereg, an associate professor of computer science who studies life systems at the University of Colorado Boulder’s Biofrontier Institute. “It both have established ecological functions that make towers, and really opens the door to conducting more controlled experiments to try to understand the perceptual world of these organisms and how they communicate within large groups.” Peleg was not involved in this study.
As a next step, Perez said her team wanted to know if the formation of these structures was a collaborative or competitive action. In other words, do towering nematodes behave socially to help each other, or do their towers resemble the stampedes on Black Friday sales?
Studying the behavior of other self-organizing creatures could provide clues to nematode social norms and help answer this question, Ding said.
David Who, professor of mechanical engineering and biology at Georgia Tech, is one of the few creatures known to cooperate like nematodes, ants assembled to form buoyant rafts to survive floods. Hu was not involved in the research.
“Alis are incredibly sacrificial to each other and generally do not fight within the colony,” Hu said. “It’s because of their genetics. They’re all from the same queen, so they’re like brothers.”
Like ants, nematodes do not appear to exhibit distinctive role differentiation or hierarchy within tower structures, Perez said. Each worm from the base to the top of the structure is equally mobile and powerful, indicating that the competition is not working. However, since lab-grown worms were essentially cloned from each other, it is not clear whether role differentiation occurs more frequently in nature, where nematode populations may have more genetic differences, she noted.
Furthermore, socially supportive creatures tend to use some form of communication, Peleg said. In the case of ants, it could be their pheromone trail, but bees rely on ritual dance routines, while slime-shaped ones use pulsating chemical signals.
However, in nematodes it is not yet clear how they communicate, or whether they communicate at all, Ding said. “The next step for (the team) is to actually choose the next question.”
In particular, there is a lot of interest in studying cooperative animal behavior among the robotics community, Hu said. One day, he added, he could use information about the complex social nature of creatures like nematodes to inform how technologies, such as computer servers and drone systems, communicate.