Watch a sea butterfly's 'flight' through the ocean


The tiny but beautiful sea butterfly, a type of plankton, uses the same physics to 'fly' through water as a fruit fly does through air. Viviane Richter reports.


Where its snail cousins may drag their weight on a slimy foot, the plankton sea butterfly Limacina helicinaI prefers to fly – dashing through the Arctic waters propelled by tiny fleshy wings.

And it turns out their “flight” through water is closer to an insect’s than previously thought, according to researchers from the Georgia Institute of Technology.

The team imaged the fluid movement around the plankton’s delicate gelatinous body floating in a tank, using a custom 3-D camera system.

When the team analysed the dynamics around the sea butterfly’s wings they realised it resembled a fruit fly’s flight – generating the same low-pressure system that produces lift in flies.

The sea butterflies clap their wings together at the tips before dragging them apart, sucking fluid into a gap between their wings. This creates low-pressure vortices at the wings’ tips which propel the creature up.

“No one has actually been able to measure the flow around an insect doing this while it is flying, and so that was kind of the holy grail of this area of research,” said study author David Murphy.

“It really surprised me that sea butterflies turned out to be honorary insects.”

The discovery was published in the Journal of Experimental Biology.

  1. http://jeb.biologists.org/content/219/4/535
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