Humans often view being multicellular as an advantage, but most life on Earth is single-celled, thriving in extreme conditions. The evolution of multicellular life, starting about 2.5 billion years ago with cyanobacteria forming colonies, remains a mystery, including the benefits it provided to early cells.
A study from the Marine Biological Laboratory highlights how cooperative feeding by Stentor, a large unicellular organism, might have influenced the evolution of multicellular life.
The research examines why independent organisms initially formed colonies before becoming fixed together. John Costello, senior author, emphasizes this backward look into evolutionary processes to uncover the forces driving such cooperation.
A stentor is a trumpet-shaped, single-celled organism up to 2 mm long. It uses its holdfast to anchor to surfaces in ponds or lakes, while its trumpet end creates a vortex to draw in food, such as bacteria.
In the lab, researchers observed that when placed in water dishes, Stentors form colonies by touching their holdfasts on the glass. Together, neighboring Stentors generate stronger vortexes, doubling the water flow to their mouths. This enables them to capture more prey, including faster-swimming ones, by pulling water from farther away.
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The feeding benefits between neighboring Stentors are uneven, with the weaker one benefiting more. When paired, their trumpet ends sway together, increasing fluid flow but oscillating apart.
Using mathematical models, researchers found that Stentors switch between partners in a “promiscuous” manner, optimizing feeding benefits. While one moves away from a neighbor, it gets closer to another, maximizing energy gain. This behavior benefits the colony, ensuring more food for all.
The Stentor of today isn’t multicellular, and its colonies are temporary, easily dispersing with a slight disturbance. While working together provides collective benefits, they separate when food becomes scarce.
Scientists observed that Stentors stay in colonies when food is abundant but go solo to forage when resources are limited—a behavior similar to how humans cooperate in times of plenty but compete when resources dwindle.
Unlike early multicellularity in models like Volvox cateri, where genetically identical cells formed colonies and later differentiated, Stentor colonies consist of genetically distinct individuals.
Researchers believe this model represents an even earlier stage in evolution when single cells temporarily cooperated for mutual benefits before returning to independence—long before multicellularity became permanent, which occurred at least 25 times across different lineages.
Journal Reference
- Shekhar, S., Guo, H., Colin, S. P., Marshall, W., Kanso, E., & Costello, J. H. (2025). Cooperative hydrodynamics accompany multicellular-like colonial organization in the unicellular ciliate Stentor. Nature Physics, 1-8. DOI: 10.1038/s41567-025-02787-y
