Volvox colony (dancing algae)
Scientists at Cambridge University have discovered that freshwater algae can form stable groupings in which they dance around each other, miraculously held together only by the fluid flows they create.
According to their paper published in the journal Physical Review Letters, the researchers studied the multicellular organism Volvox, which consists of approximately 1,000 cells arranged on the surface of a spherical matrix about half a millimetre in diameter.
Each of the surface cells has two hair-like appendages known as flagella, whose beating propels the colony through the fluid and simultaneously makes them spin about an axis.
Volvox fluid flow
The researchers found that colonies swimming near a surface can form two types of “bound states”; the “waltz”, in which the two colonies orbit around each other like a planet circling the sun, and the “minuet”, in which the colonies oscillate back and forth as if held by an elastic band.
The researchers, which include PhD students and postdoctoral researchers, have developed a mathematical analysis that shows these dancing patterns arise from the manner in which nearby surfaces modify the fluid flow near the colonies and induce an attraction between them.
The observations constitute the first direct visualisations of the flows, which have been predicted to produce such an attraction.