Worm towers: Nematodes build living structures that puzzle scientists

Long believed to be confined to the lab, the bizarre and cooperative behavior of “worm towers” has now been documented in nature.

An international team of researchers has recorded the first direct evidence of nematodes forming vertical, living structures in decaying fruit in German orchards. It’s a phenomenon once thought to be mythical.

These living towers, built from worm bodies, act as a collective vehicle to reach new environments and improve survival under stress.

Worm towers step into nature

For years, scientists suspected that nematodes might build these structures in the wild, but evidence was lacking.

Although seen in labs and chambers, no one had documented them in the wild – until now. Researchers from the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz have changed that.

“I was ecstatic when I saw these natural towers for the first time,” said Serena Ding, senior author and group leader at MPI-AB, recalling the moment a colleague shared video footage from the field.

“For so long natural worm towers existed only in our imaginations. But with the right equipment and lots of curiosity, we found them hiding in plain sight.”

Ryan Greenway, a technical assistant at MPI-AB, spent months scouring rotting apples and pears with a digital microscope in local orchards near the University of Konstanz. His patience paid off.

In several cases, he observed the worms forming elaborate, upright clusters. When the team brought some into the lab for study, they made a surprising discovery. Despite many nematode species, the towers were made only from one kind, in a tough, immobile “dauer” larval state.

More than a pile of worms

“A nematode tower is not just a pile of worms,” said first author Daniela Perez, a postdoctoral researcher at MPI-AB. “It’s a coordinated structure, a superorganism in motion.”

In the wild, individual dauer-stage nematodes stand on their tails to latch onto passing animals, hitching rides to new environments. But this study revealed that entire towers – dozens of worms high – can perform the same trick collectively.

The towers responded to touch, detached from surfaces, and even managed to cling en masse to insects like fruit flies. It’s group movement on a microscopic scale.

To test the behavior under controlled conditions, Perez created worm towers in the lab. She used Caenorhabditis elegans, a commonly studied nematode species.

By placing starved worms on food-free agar with a bristle, she saw them build towers within two hours. These structures remained stable for over 12 hours, sometimes forming exploratory “arms” that extended into the surrounding space or bridged gaps to reach new surfaces.

“The towers are actively sensing and growing,” Perez said. “When we touched them, they responded immediately, growing toward the stimulus and attaching to it.”

Climbing together as one

In the wild, only dauer-stage worms built towers, but in the lab, Perez saw adults and other larval stages also built them. This suggests the behavior may be more common and versatile than previously believed.

Despite their impressive structure, the towers showed no evidence of specialization. Worms at the base were just as mobile and fertile as those at the top.

“C. elegans is a clonal culture and so it makes sense there is no differentiation within the tower,” the authors explained. “In natural towers, we might see separate genetic compositions and roles, which prompts fascinating questions about who cooperates and who cheats.”

This kind of egalitarian cooperation – where no individual appears to dominate or be sacrificed – raises new questions about how group behaviors evolve and how individual actions contribute to collective success.

Worm towers inspire models

These findings place nematodes in a very exclusive group. Until now, only a few animals – like slime molds, fire ants, and spider mites – were known to use body-linking for collective motion.

The discovery that nematodes, Earth’s most abundant animals, do the same in nature opens vast research possibilities.

“Our study opens up a whole new system for exploring how and why animals move together,” Ding said. “By harnessing the genetic tools available for C. elegans, we now have a powerful model to study the evolution of collective dispersal.”

As scientists continue to explore how cooperative behaviors arise in everything from insect colonies to migrating birds, the humble worm tower may now rise – literally and figuratively – as a new cornerstone in the study of group movement.

What was once a lab oddity has become a natural wonder, twisting upward in decaying fruit, silently revealing how animals – even the tiniest – can work together to reach for better places.

The study is published in the journal Current Biology.

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