Nematode Tower Power
upstart writes:
Living worm towers are recorded in the wild for the first time, a rare example of collective hitchhiking in nature
- First evidenceof "living towers" in nature: observed in rotting apples and pears from local orchards in Konstanz, Germany
- Tower function confirmed: towers can attach to passing insects and can bridge physical gaps to disperse
- A powerful model:C. elegans are a new a tool for studying the ecology and evolution of collective dispersal
Nematodes are the most abundant animal on earth, but when times get tough, these tiny worms have a hard time moving up and out. So, they play to the strength of their clade. If food runs out and competition turns fierce, they slither towards their numerous kin. They climb onto each other and over one another until their bodies forge a living tower that twists skyward where they might hitch a ride on a passing animal to greener and roomier pastures.
At least that's what scientists assumed. For decades, these worm structures were more mythical than material. Such aggregations, in which animals link bodies for group movement, are rare in nature. Only slime molds, fire ants, and spider mites are known to move in this way. For nematodes, nobody had even seen the aggregations-known as towers- forming anywhere but within the artificial confines of laboratories and growth chambers; and nobody really knew what they were for. Did towers even exist in the real world?
Now, researchers in Konstanz, Germany, have recorded video footage of worms towering in fallen apples and pears from local orchards. The team from the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz combined fieldwork with laboratory experiments to provide the first direct evidence that towering behavior occurs naturally and functions as a means of collective transport.
"I was ecstatic when I saw these natural towers for the first time," says senior author Serena Ding, group leader at the MPI-AB, of the moment when co-author Ryan Greenway sent her a video recording 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."
Greenway, a technical assistant at the MPI-AB, spent months with a digital microscope combing through decaying fruit in orchards near the university to record natural occurrences and behavior of worm towers. Some of these whole towers were brought into the lab. What was inside the towers surprised the team. Although the fruits were crawling with many species of nematodes, natural towers were made only of a single species, all at the tough larval stage known as a "dauer."
"A nematode tower is not just a pile of worms," says the first author Daniela Perez, a postdoctoral researcher at MPI-AB. "It's a coordinated structure, a superorganism in motion."
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