Some of nature’s most unusual finds remain unrecognized for decades, or even centuries, after their initial discovery—and that has proven true once again with several strange new creatures recently uncovered in museum collections and from other sources.
The findings reveal at least ten new examples of some of the animal kingdom’s strangest worms, showcasing their remarkable diversity and a few unusual traits, such as bodies that appear to repeatedly branch into multiple different ends, almost evoking the fantastic beasts of ancient mythology.
Such characteristics, however, are what earned these creatures their unique name: branching worms. These marine animals belong to a group of creatures known as annelids and possess a single head but grow elaborate, almost plant-like networks of branching bodies.
The creatures are known to science, although they are reclusive, spending most of their lives hidden inside sea sponges that thrive in a range of different ocean environments, with their many branching appendages spreading throughout the internal structures of their aquatic hosts.
New Examples of Earth’s Strangest Worms
Previously, only three varieties of these oceanic oddities were known. However, a new study published in the Zoological Journal of the Linnean Society has revealed as many as ten likely new species, some of which had been hidden away in museum collections for more than a century.
The study, led by researchers at the University of Göttingen, used the specimens, along with genetic data and other information, to reconstruct the evolutionary history of the animals with the help of DNA sequencing, anatomical analyses, and several newly collected specimens.
Based on their findings, a total of thirteen distinct forms of branching worms are now known, which are found across the Indo-Pacific, the Red Sea, and the ocean waters near New Zealand. Based on the available genetic data, these creatures appear to stem from two major evolutionary lineages: Ramisyllis, a genus that was already known to researchers, and now an entirely new genus, which has been dubbed Cladosyllis.
“Our findings would have been impossible without access to valuable museum specimens,” said study leader Professor Maria Teresa Aguado, Scientific Curator of the Biodiversity Museum at Göttingen University. “These collections are not just repositories of old samples, but resources that continue to generate new discoveries.”
Hidden in Plain Sight
Remarkably, some of these specimens had been accessible to researchers for more than a century. Several of the newly assessed early specimens were retrieved from within sponges held in the Senckenberg collection, which dates to 1914.
Researchers were successfully able to reveal these “hidden” specimens without damaging their hosts by using micro-computed tomography (micro-CT) imaging.
However, along with the discoveries, a few answers to longstanding questions have also emerged.
Going back to the nineteenth century, many of these rare branching worms were classified as a single widespread species. However, now researchers say that a far more diverse evolutionary family exists, with various kinds associated closely with specific sponge hosts in each of the geographic regions where they reside.
Some of the newly identified specimens inhabit sponges that thrive in shallow water, while others dwell within glass sponges, a species that is found at depths exceeding 1,000 meters below the surface. This reveals the level of specialization among different hosts, which the research team believes has been a driving force behind the diversity of these bizarre worms that have evolved to rely on them.
Despite their special adaptations, it is nonetheless believed that all branching worms evolved from a common ancestor, meaning that their very unusual body plan evolved only once, and thereafter produced two major lineages with some physical differences.
The research team believes there are likely to be other undiscovered varieties of branching worms out there, and thanks to the new research, discovering them could be more feasible in the near future, and may reveal additional insights into these bizarre ocean worms and their unique evolutionary place in marine biodiversity.
The study, “Many Branches, One Lineage: Museomic Insights into the Diversity and Evolution of Branching Syllid Worms,” appeared in the Zoological Journal of the Linnean Society.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.