A newly discovered ribbon worm off the coast of northwest Spain has a strange party trick: it compresses itself into a set of tight, symmetrical rings, collapsing to just one-fifth of its full length—like a living accordion.
The species, Pararosa vigarae, was found about 30 meters underwater, lurking beneath rocks in the Galician subtidal zone. When fully stretched, it measures around 25 centimeters (nearly 10 inches). But when it contracts, it pulls itself into a tight, corrugated form, literally folding in on itself.
This isn’t just your standard worm wiggle. “These rings are not regularly distributed as observed in the accordion worm,” lead researcher Dr. Aida Verdes of Spain’s National Museum of Natural Sciences, told IFLScience. Even when fully extended, the rings are still visible—marking P. vigarae as something genuinely different from its relatives.
This Newly Discovered Worm Folds Like an Accordion and Hunts With Venom
The discovery, published in Royal Society Open Science, confirms Pararosa vigarae as not just a new species, but a new genus within the family Lineidae. It belongs to the Nemertea phylum—a group of venomous, predatory worms known for their stealthy hunting and low-key brutality in the food chain. These aren’t like your standard earthworms. Nemerteans use specialized toxins to paralyze and consume prey, and they’ve evolved to thrive in some of the ocean’s more overlooked environments.
Verdes and her team used genetic sequencing alongside physical observations to place this worm in the larger evolutionary picture. While other ribbon worms contract and wrinkle, this one folds in clearly defined rings, similar to traits found in a completely different class of ribbon worms. That might mean this accordion-style compression evolved more than once, which would make it a rare example of convergent evolution in the group.
It’s a strange enough move on its own, but P. vigarae also brings a sweet, personal detail: it’s named after Rosa Vigara, the wife of the study’s senior author, as a golden wedding anniversary gift. Not the most conventional tribute—but definitely memorable.
Verdes said the find proves how much we still don’t know, even in well-studied regions. “The coast of Galicia is the area where most nemertean species are known… [and yet] we still find new species with unique behaviors.”
Pararosa vigarae may be small, but its design is anything but simple—another example of how evolution never ceases to amaze.
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