Some creatures are so extraordinary they feel like they’ve leapt straight from the pages of a science-fiction novel. Among them are the polychaetes, strange marine worms with abilities that continue to surprise scientists. Not only can these animals regenerate most of their bodies, but they also build intricate structures in a way that researchers compare to a living 3D printer.

Worms with a hidden superpower

Polychaetes, which number over 24,000 species worldwide, are equipped with appendages called parapodia — bristly outgrowths that help them swim, crawl, or dig through the seafloor. What fascinates researchers is not just their bizarre anatomy, but their unmatched skill in regeneration. According to Florian Raible, a molecular biologist at the University of Vienna, these worms “can regenerate large portions of their body far more effectively than many other organisms.”

While studying Platynereis dumerilii, postdoctoral researcher Kyojiro Ikeda observed something striking: cells in the worms called “blasts” extend and retract repeatedly, depositing chitin — a natural biopolymer — to form new bristles, teeth, or hooks. Each structure is crafted by a single cell, almost like a biological printer laying down material layer by layer.

Lessons for human health

What makes this discovery even more intriguing is its similarity to human biology. Raible notes a “remarkable resemblance” between these worm cells and the sensory cells of the human inner ear, which play a critical role in hearing. This suggests that studying polychaetes could not only advance regenerative biology but also provide insights into conditions like hearing loss.

The material they produce — chitin — is already known as the second most abundant biopolymer on Earth and is well tolerated by the human body. Scientists believe it could inspire new applications in medicine, from biodegradable surgical sutures to dental cement and even advanced adhesives.

A world stranger than fiction

Polychaetes are far from the simple “worms” many imagine. Some, like the giant Gippsland earthworm in Australia, stretch nearly three meters long. Others glow in the dark with bioluminescence, while bloodworms use venomous jaws to devour prey. Their diversity and adaptability have fascinated researchers like Conrad Helm of the University of Göttingen, who calls their biology “mind-blowing.”

During experiments, scientists even observed that polychaetes form new teeth every 30 to 40 minutes — a conveyor-belt-like process of constant renewal. For researchers, this discovery underscores the importance of fundamental science. As Helm explains, “Without basic research, materials and biological processes like these could never be applied in medicine.”

Ancient teachers of modern science

These worms have been around for more than 500 million years — predating the first trees by about 100 million. Their resilience and evolutionary success make them not just survivors, but teachers. In their overlooked, alien-like bodies may lie solutions for future medicine, materials, and our understanding of life itself.