It turns out sea anemones had a back before it was cool. A new study reveals that these ancient creatures use a molecular mechanism so fundamental, it may date back 600 million years — rewriting our understanding of animal evolution.
Key Points at a Glance
- Sea anemones use a “BMP shuttling” system to form their back-to-belly body axis
- This mechanism was thought unique to bilaterally symmetric animals
- Findings suggest BMP shuttling predates the split between cnidarians and bilaterians
- Discovery opens new perspectives on the evolutionary roots of body plans
In a discovery that links modern developmental biology to the dawn of complex life, researchers at the University of Vienna have shown that sea anemones — those tentacled, flower-like marine creatures — use a molecular system for organizing their bodies that was previously thought exclusive to more complex animals like humans, frogs, and flies.
Published in Science Advances, the study reveals that sea anemones use a process called BMP shuttling to pattern their body axis from back to belly. This same process, involving a protein called Chordin that distributes and modulates Bone Morphogenetic Proteins (BMPs), is used in a wide array of bilaterian animals — those with bilateral symmetry like vertebrates and insects.
“We discovered that sea anemones, which appear radially symmetrical, actually use the same molecular tricks to build a bilateral body layout as animals that have clear left and right sides,” said postdoctoral researcher David Mörsdorf, lead author of the study. “That mechanism seems to be incredibly ancient.”
To find this out, the team blocked the production of Chordin in sea anemone embryos, which halted BMP signaling and disrupted body axis formation. They then introduced two versions of Chordin — one that was fixed in place and one that could diffuse through the embryo. Only the diffusible version restored the proper patterning, proving that Chordin in sea anemones acts as a BMP shuttle, just like in frogs or flies.
This matters because it challenges the view that bilateral symmetry — and the complex body structures it supports — evolved independently in multiple animal lineages. Instead, it supports the idea that a shared ancestor of bilaterians and cnidarians, some 600–700 million years ago, already had the molecular machinery for creating a body axis using BMP shuttling.
“We might never be able to fully confirm if symmetry evolved once or multiple times,” said Grigory Genikhovich, senior author of the study. “But the presence of this shared molecular mechanism across radically different animals makes a strong case for a common evolutionary origin.”
Although not all animals use BMP shuttling — for example, fish don’t, while frogs do — its repeated appearance across evolutionary distant species hints at its deep evolutionary roots. The findings also show how much complexity can be hidden in seemingly simple creatures.
Sea anemones might not look like they have a “back,” but at the genetic and molecular level, they do — and they use ancient developmental tools to build it. This opens new doors in understanding how body plans evolved in early animals, potentially offering fresh insights into the origins of complexity itself.
The research, supported by the Austrian Science Fund, underscores how investigating evolutionary relics like sea anemones can illuminate the shared biology underlying life’s diversity.
Source: University of Vienna
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