Scientists have discovered that nematodes, tiny roundworms, can form coordinated living towers to hitch rides with passing insects during times of food scarcity. Researchers from the Max Planck Institute of Animal Behavior and the University of Constance documented the collective behavior in nature for the first time.

The nematodes, specifically Caenorhabditis elegans, were observed in orchards near Constance, climbing on top of each other to escape from rotting apples and pears. The researchers brought some of the natural towers into the laboratory, providing the first direct evidence that the tower-building behavior occurs naturally.

Nematodes are among the most common animals on Earth, with around 20,000 known species. They are often only one to three millimeters in size and have adapted to nearly every ecosystem, both on land and in water. Despite their small size, they demonstrate social complexity and, when the need arises, are capable of complex cooperation.

After months of inspecting rotting fruit in local orchards, the research team, which included co-author Ryan Greenway, observed hundreds of one-millimeter-long nematodes climbing on top of each other to form stable living towers. Some constructions even stretched bridges across gaps to reach new areas of nutrient medium. All life stages of the nematodes, from baby worms to adults, participated in these microscopic worm towers.

"A nematode tower is not just a pile of worms. It is a coordinated structure, a superorganism in motion," said Daniela Perez, a postdoctoral researcher at the Max Planck Institute of Animal Behavior and first author of the study, according to Smithsonian Magazine. These towers move back and forth as a unit, responding to external stimuli. When touched, they responded immediately, growing toward the stimulus and adhering to it. "They feel it, and then the tower moves toward this stimulus and attaches to our metal rod or a buzzing fly," Perez said.

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In laboratory conditions, researchers reproduced the construction process by placing hungry nematodes in a limited space. Within two hours, the worms began to self-organize, forming stable towers up to several millimeters high that maintained their structure for more than 12 hours. There was no clear role differentiation among the worms; individuals at the base or the top were equally mobile, fertile, and vital.

The researchers discovered that entire towers of worms could respond to touch, detach from surfaces, and collectively adhere to insects such as fruit flies, moving en masse to new environments. This behavior, known as phoresy, allows nematodes to be carried to new habitats, suggesting it may be a more widespread strategy of group movement than previously believed. "If you think about it, an animal that is one millimeter long cannot just crawl all the way to the next piece of fruit that is two meters away," Perez explained, according to Het Nieuwsblad.

The study, published in the scientific journal Current Biology, provides the first evidence that nematode towers serve a hitchhiking capacity in nature. The researchers noted that aggregations in which animals move their bodies as a unit are relatively rare in nature. "Our study allows us to explore in a whole new way how group movement arises and functions," said Serena Ding, head of the Max Planck research group for Genes and Behavior, according to Scientias.

The egalitarian nature of these communities is of particular interest. The scientists found that within the towers, there was no distinction between individuals; worms at the base or the top were equally capable. However, they suggest that more complex social strategies may exist in natural populations. "Perhaps some individuals contribute to the tower building, while others act as free riders, benefiting from the work of others without participating themselves," the scientists stated, according to n-tv.

The research team plans to further investigate whether the structures the worms build are a result of cooperative or competitive behavior. "We saw that they react very strongly to the presence of a stimulus," Perez said, according to Het Nieuwsblad. "With the genetic tools of C. elegans, we can finally study the ecology and evolution of collective dispersal in depth," Perez noted, according to Scientias.