These tiny worms form 'living towers' and become a 'superorganism' to survive

They measure just a millimeter in length, but when united they become a superorganism . 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 group together in tens or even thousands to reach and conquer new spaces.

Until now, these aggregations were almost mythological. They had only been observed in highly controlled laboratory settings, and not spontaneously . But researchers in Konstanz, Germany, have recorded images of maggots of the genus Caenorhabditis towering over fallen apples and pears in local orchards. The team from the Max Planck Institute for Animal Behavior and the University of Konstanz combined field work with laboratory experiments to provide the first direct evidence that the behavior of towering in living towers occurs naturally and functions as a means of collective transport for the nematode maggots. The finding was published this Thursday in the journal Current Biology .

Serena Ding, a Max Planck researcher and lead author of the study, explains that nicitation—the behavior in which the worm stands upright, stands on its tail, and moves its body in the air as if hitchhiking—has already been studied by other research groups. However, her latest research addresses the collective aspect of dispersal, showing that worms also group together to attach themselves to fruit flies or other insects and thus “hitchhike” on them. Ding had already noticed this behavior occurring spontaneously in her laboratory cultures when she left plates of nematodes unattended. “These plates often developed fungal contamination or other more complex structures that the hungry worms used as scaffolding to climb,” she explains.

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

That wasn't the only surprise. Traditionally, science had linked nicitation to a very specific life stage of nematodes: the dauer stage. This is the name given to an "alternative" larval stage that worms adopt to survive in 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 nematode tower isn't just a pile of worms. It's a coordinated structure that displays a certain directionality during its formation, especially when they sense the presence of potential mass transportation. "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're sensitive to touch. They also tend to line up within the tower, with their heads pointing in the direction they want to move, which suggests an unusual degree of coordination for such a small animal.

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, they emerged as living towers that remained stable for more than 12 hours and were able to extend their exploratory arms into the surroundings. Some even formed bridges across certain gaps to reach new surfaces.

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

Compared to other collective transport systems in animals—such as 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 a new avenue for exploring how and why animals move together. Furthermore, with their slimy, limbless bodies, the formation of tall structures in worms is quite remarkable. If scientists can understand how these non-adherent 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,” Ding ventures.