Research · Ten New Branching Worm Species Hiding in Sea Sponges — One Traced to a 1914 Japanese Specimen
Researchers at the University of Göttingen have identified thirteen distinct forms of branching marine worms — at least ten of them likely new species — using genomic data combined with anatomical analysis.
These bizarre animals live in symbiosis inside sea sponges, each with a single head leading into a tree-like network of branches that spreads through its host. Adapting to different sponge hosts appears to have driven their diversification: some inhabit deep-sea glass sponges at depths of up to 1,000 metres, while others live in shallow-water sponges. The team found the unusual branching body plan evolved only once, then split into two major lineages — one in the genus Ramisyllis and another placed in an entirely new genus, Cladosyllis.
For more than a century, these worms were classified as a single widespread species despite turning up across the world's oceans — a taxonomy puzzle dating back to the nineteenth century. Museum collections proved decisive: using micro-CT imaging, the team revealed a worm of the new genus Cladosyllis inside a deep-sea glass sponge collected in 1914 from Sagami Bay, Japan. The result is a reminder that natural-history collections can still generate discoveries from biodiversity that went undetected for over a hundred years.
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