Tiny worms form living towers to become a super-organism

They measure just a millimeter in length, but when united, they become a super-organism. Nematodes are the most abundant animals on the planet and have one of the rarest abilities in the natural world: they can climb on top of each other until their bodies form a living tower. If food becomes scarce or competition for it becomes fierce, these tiny worms band together — sometimes by the dozens, even thousands — to reach and colonize new spaces.

Until now, such groupings were almost mythical. They had only been observed under highly controlled laboratory conditions, and never spontaneously. But researchers in Konstanz, Germany, have captured footage of Caenorhabditis worms climbing over fallen apples and pears in local orchards. The team from the Max Planck Institute of Animal Behavior and the University of Konstanz combined fieldwork with lab experiments to provide the first direct evidence that this tower-building behavior occurs in nature — and that it functions as a form of collective transportation for nematodes. The discovery was published Thursday in the journal Current Biology.

Serena Ding, a researcher at Max Planck and lead author of the study, explains that “nictation” — the behavior in which a worm stands upright, balances on its tail, and waves its body in the air as if hitchhiking — had already been studied by other research groups. However, this new investigation explores the collective dimension of dispersal, showing that the worms also group together to attach themselves to fruit flies or other insects, effectively “riding” them to new locations.

Ding had previously noticed this behavior happening spontaneously in her lab cultures when she left nematode plates unattended. “These plates often developed fungal contamination or other complex structures that the hungry worms used as scaffolds to climb,” she explains.

Then came a video that changed everything. Ryan Greenway, a co-author of the study, sent Ding a recording of a group of nematodes forming bridges between rotting fruit in an orchard near the university. “For a long time, natural worm towers existed only in our imagination,” the researcher recalls. “But with the right tools and a lot of curiosity, we found them hiding in plain sight,” she adds.

The co-author of the study set up a field microscope with which he was able to record the first video of natural towers in nematodes.Serena Ding

That wasn’t the only surprise. Traditionally, science had linked nictation to a very specific stage in the life of nematodes: the dauer stage. This refers to an “alternative” larval phase that the worms enter in order to survive under adverse conditions. “Our observations revealed that worms of all ages can form towers, which suggests that a different molecular mechanism than we thought could be involved,” explains the author.

Cooperation or death trap

A tower of nematodes is not just a pile of worms. It is a coordinated structure that shows a certain directionality during its formation, especially when the worms detect potential mass transport opportunities.

“For example,” Ding notes, “when we touch the towers with a needle, the worms tend to move more and crawl toward that signal.” In other words, they are sensitive to touch. They also tend to align themselves within the tower, with their heads pointing in the direction they intend to move, which suggests a remarkable level of coordination for such small animals.

The results of the research illustrated by one of the authors of the study.Daniela Perez

When placed on agar — a gelatinous substance used as a growth medium in microbiology — without food and with a toothbrush bristle serving as a post, the hungry worms began to self-assemble. Within two hours, living towers emerged that remained stable for over 12 hours and were capable of extending exploratory arms into their surroundings. Some even formed bridges across gaps to reach new surfaces.

“We suspect that in addition to touch, odor detection in nematodes could play an important role,” Ding explains. “Chemical cues could help worms locate resources or vectors, improving the efficiency of collective dispersal.”

Compared with other collective transport systems in animals — like schools of fish or flocks of birds — worm towers are somewhat different. “There is a very strong physical overlap between individuals and very little long-distance coordination,” the expert explains.

Furthermore, despite the architectural complexity of these structures, the worms inside them showed no obvious role differentiation, suggesting a form of egalitarian cooperation. “We are exploring whether there is a division of labor — which would suggest cooperation — or social cheating — which would be competition between individuals — in the formation of towers, since only some individuals in the group manage to disperse successfully.”

The new study opens up a path to explore how and why animals move together. Additionally, given that worms have limbless, sticky bodies, their ability to form tall structures is quite remarkable. If scientists can understand how these non-adhesive organisms build and maintain towers, it could inspire new ideas in mechanics and materials engineering.

“Although it’s still early days, this could have applications in the design of soft robotics, bio-inspired materials, or in understanding collective mechanics in other biological or technological systems,” says Ding.

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