Nematodes, the most abundant animals on our planet, face challenges in their mobility during difficult times. These minute worms, when confronted with food scarcity and increasing competition, turn to an ingenious survival strategy that leverages the strength of their population. When resources dwindle, they instinctively migrate toward their fellow nematodes, creating interwoven structures that rise toward the sky. These formations, known as towers, allow them to potentially hitch a ride on passing animals, seeking more favorable and spacious environments.

For many years, scientists speculated about the existence of these aggregates, which enable several organisms to move in unison. Such collective movement is rarely observed in nature, with only a handful of species like slime molds, fire ants, and spider mites known to exhibit similar behavior. However, prior to recent research, even the concept of nematode towers was largely theoretical, as no one had documented their formation outside of laboratory settings. This raised significant questions: Do nematode towers truly exist in the wild, and if so, what purpose do they serve?

In an exciting breakthrough, researchers from Konstanz, Germany, have captured video evidence of these worm towers in their natural habitat, specifically within decaying apples and pears from local orchards. The collaborative team from the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz combined rigorous fieldwork with controlled laboratory experiments to document the first concrete proof that nematodes do indeed form towers in nature as a means of collective movement.

“I was ecstatic when I saw these natural towers for the first time,” expressed senior author Serena Ding, who leads a group at the MPI-AB. This moment of discovery came when co-author Ryan Greenway sent her the captivating video footage during their research. “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.”

Greenway, a technical assistant at MPI-AB, dedicated months to studying decaying fruit in local orchards using a digital microscope, meticulously documenting instances of natural worm tower formations. His efforts led to the collection of some of these towers, and what the team found inside was unexpected. While various nematode species inhabited the fruits, the towers themselves were composed solely of a single species, all in the resilient larval stage known as “dauer.”

“A nematode tower is not just a pile of worms,” stated Daniela Perez, the first author and a postdoctoral researcher at MPI-AB. “It’s a coordinated structure, a superorganism in motion.” This statement underscores the complexity and functionality of these towers, which were observed to wave in unison, akin to individual nematodes that elevate themselves on their tails to attach to passing insects. Key findings revealed that entire towers could respond to physical contact, detach from surfaces, and collectively latch onto insects like fruit flies. This behavior effectively allows them to migrate en masse to new environments.

To delve deeper into the mechanics behind this behavior, Perez constructed a controlled tower in the lab using cultured C. elegans nematodes. When placed on food-free agar alongside a small vertical post, the hungry worms began to self-organize. In a remarkable display, living towers formed within two hours, remaining stable for over 12 hours and demonstrating the ability to extend exploratory “arms” to engage with their surroundings. Some even constructed bridges to span gaps and reach new surfaces.

“The towers are actively sensing and growing,” Perez explained. “When we touched them, they responded immediately, growing toward the stimulus and attaching to it.” This fascinating behavior was not limited to the dauer larval stage observed in natural samples; adult C. elegans and all larval stages in the laboratory also exhibited the ability to form towers. Such findings hint that this towering behavior may represent a more ubiquitous strategy for collective movement than previously understood.

Despite the apparent complexity of these structures, the researchers noted that no significant role differentiation was observed among the worms. Individuals at both the base and the top of the tower demonstrated similar mobility, fertility, and strength, suggesting an egalitarian style of cooperation among the nematodes within the tower. However, the authors cautioned that this observation was confined to the controlled laboratory environment. “C. elegans is a clonal culture, so it makes sense that there is no differentiation within the tower. In natural towers, we might see diverse genetic compositions and roles, prompting intriguing questions about cooperation and competition among different nematodes.”

As scientists continue to investigate the evolution of group behaviors—ranging from insect swarms to bird migrations—these microscopic worm towers may unlock significant insights into how and why animals move collectively. “Our study opens up a whole new system for exploring how and why animals move together,” Ding emphasized, as she leads ongoing research into the behavior and genetics of nematodes. “By utilizing the genetic tools available for C. elegans, we now have a powerful model for studying the ecology and evolution of collective dispersal.”