Press release: Decades-old museum specimens reveal ten extraordinary new worms
No. 113 - 02.09.2026
International research team mines museum collections to solve 147-year-old evolutionary mystery
Scientists have discovered that one of the most unusual creatures in the animal kingdom is far more diverse and evolutionarily complex than previously known. An international team led by the University of Göttingen has reconstructed the evolutionary history of branching marine worms – rare annelids that live hidden inside sea sponges and whose bodies branch repeatedly into multiple posterior ends. Until now, only three species of branching worms have been identified. By combining DNA sequencing of museum specimens with newly collected specimens and detailed anatomical analyses, the researchers discovered ten new species and solved a long-standing puzzle dating back to the nineteenth century. The results were published in the Zoological Journal of the Linnean Society.
Branching worms are among the strangest animals known to science. Unlike typical worms, they possess a single head that gives rise to a tree-like network of branches. These species live in symbiosis with and inside sponges, where their unusual body architecture allows them to spread throughout their host. Using genomic data obtained from both newly collected specimens and decades-old museum material, the researchers found that branching worms form a distinct evolutionary group comprising two major lineages: one group belongs to the genus Ramisyllis, while the second was assigned to a completely new genus, Cladosyllis. “Our findings would have been impossible without access to valuable museum specimens. These collections are not just repositories of old samples, but resources that continue to generate new discoveries,” said Professor Maria Teresa Aguado, Scientific Curator of the Biodiversity Museum at Göttingen University and leader of the study.
The researchers also found a remarkable level of hidden diversity, which had remained undetected for more than a century despite these worms being present in a huge part of the world’s oceans. The team identified thirteen distinct forms of branching worms, including at least ten likely new species distributed across the Indo-Pacific, the Red Sea and New Zealand. The study suggests that specialization on different sponge hosts played a key role in driving diversification and evolution: some species inhabit deep-sea glass sponges at depths of up to 1,000 metres, while others live in shallow-water sponges.
“For over a century, the rare branching worms were all classified as a single widespread species. However, we have shown that – like their bodies – their family tree has many branches, each closely associated with its own sponge species and located in specific areas,” said Dr Guillermo Ponz Segrelles, coauthor of the study. Beyond solving the puzzle of how to classify these creatures, the research provides new insights into the evolution of animal bodies. The study demonstrates that all branching worms descended from a common ancestor, meaning that their extraordinary body architecture evolved only once. The researchers also discovered that, despite their overall similarity, the two major lineages produce their branches in different ways, highlighting the developmental flexibility that can arise during evolution.
“Some of the sponges hiding these worms came from the Senckenberg collection and date back to 1914,” notes Dr Ekin Tilic at the Senckenberg Research Institute and Natural History Museum Frankfurt and co-author of the study. “We were able to reveal the worms without damaging the sponges by using microCT imaging – modern techniques are helping us rediscover hidden biodiversity in centuries-old collections.” The researchers believe that many more branching worm species remain undiscovered and that these animals could be an important model for studying the evolution of complex body forms, symbiosis and biodiversity in marine ecosystems.
Original publication: Aguado et al (2026). Many Branches, One Lineage: Museomic Insights into the Diversity and Evolution of Branching Syllid Worms. Zoological Journal of the Linnean Society. DOI: 10.1093/zoolinnean/zlag120
Contact:
Professor M Teresa Aguado
Scientific Curator Biodiversity Museum
University of Göttingen
Animal Evolution and Biodiversity Research Group
Tel: +49 (0)551 39-25536
Email: aguadomolina@uni-goettingen.de
www.uni-goettingen.de/en/623758.html
Dr Guillermo Ponz-Segrelles
IES Profesor Máximo Trueba, Madrid, Spain
Tel: +34 (0)689402289