In a fascinating revelation, nematodes have been witnessed forming writhing towers of tiny worms in their natural habitat for the first time. This significant finding was reported in the esteemed journal Current Biology. Previously, this bizarre behavior was only observed in controlled experimental settings, where it was thought to be a competitive strategy to escape from the group. However, recent footage captured in the wild suggests a more mutually beneficial motivation behind this intriguing behavior.
The captivating images of these worm towers were recorded by a team of researchers from the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz. The footage was taken in local orchards, specifically on fallen apples and pears, showcasing nematodes engaging in their tower-forming behavior. By combining these natural observations with subsequent laboratory experiments, the researchers were able to demonstrate that this “towering” behavior occurs naturally and serves as a means of mass transit for the worms.
“I was ecstatic when I saw these natural towers for the first time,” expressed Serena Ding, the senior author and group leader at MPI-AB. She recalled the moment when co-author Ryan Greenway, a biologist at the University of Konstanz, shared a video from the field. “For so long, natural worm towers existed only in our imaginations. But with the right equipment and a lot of curiosity, we found them hiding in plain sight.”
This research also unveiled interesting aspects of worm cooperation. While many nematode species were observed crawling inside the fruit, only one species in a specific developmental stage, known as the “dauer” larval stage, actively participated in the construction of the towers. This level of species specificity suggests that there are underlying factors driving this behavior, rather than it being a random clustering of creatures.
“A nematode tower is not just a pile of worms,” noted Daniela Perez, the study's first author and a postdoctoral researcher at MPI-AB. “It’s a coordinated structure, a superorganism in motion.” The findings propose that these observations might serve as a missing link in understanding the behavior of similar organisms. While towering behavior has been observed in other species like slime molds, fire ants, and spider mites, it remains relatively rare in nature.
To investigate whether other types of worms could also form such a “superorganism,” the researchers created conditions to encourage the well-studied roundworm Caenorhabditis elegans to assemble into similar structures. Using a toothbrush bristle as a scaffold on a food-free agar plate, the team unleashed the worms. Remarkably, within two hours, the C. elegans formed a tower around the bristle, with some worms extending exploratory “arms” and others bridging gaps between spaces.
When researchers tapped the top of the tower with a glass pick, the worms responded by wriggling toward the stimulus. “The towers are actively sensing and growing,” said Perez. “When we touched them, they responded immediately, growing toward the stimulus and attaching to it.” This observation led the researchers to ponder whether a worm hierarchy dictated the activities within the tower. Did younger or stronger worms do most of the work? Surprisingly, the study revealed that the roundworms displayed a remarkably egalitarian approach, with worms of various life stages contributing equally to the tower formation.
This suggests that towering may be a more generalized strategy for group movement than previously thought. “Our study opens up a whole new system for exploring how and why animals move together,” concluded Ding. The discovery of nematodes forming towers in the wild not only enhances our understanding of these intriguing creatures but also sheds light on the complexities of animal behavior and cooperation.
