Limacina helicina, a species of tiny sea snails found in the chilly waters near the North and South Pole, are often called “sea butterflies” for the way they beat their wing-like appendages to glide through water. Now, scientists from Johns Hopkins have discovered that the snails don’t just look like butterflies, they use the same type of winged motion to “fly” through the water that insects use to move through the air.
The video footage below, captured by David Murphy, demonstrates the first time anyone has been able to analyze the motion of these tiny creatures in detail. His team set up four high-speed cameras in a tank and focused them on a cube of water only two centimeters long on each side. By mixing tiny particles with the seawater and illuminating them with lasers, they were able to track water flow as the snails moved through the tank.
While this may not seem like a shocking finding, it is pretty strange compared to other small marine life. Most zooplankton use their appendages as paddles to push themselves through the water, relying on drag to keep themselves in motion. Sea butterflies, however, flap their wings like a fruit fly to generate lift. Their wings move in the same distinct figure-eight pattern as an insect, but much, much slower.
In fact, studying sea butterflies might actually help scientists better understand the movement of insects. Fruit flies beat their wings at a rate of 200 beats per second, making it incredibly hard to track the aerodynamics of their flight. Sea snails, on the other hand, move along at a pace of just five beats per second. Still, it’s not a perfect comparison: while insect bodies stay relatively still in flight, the sea snails’ bodies can roll up to 60 degrees in each direction with every beat.
Perhaps the most exciting implication of this finding is what it means for the development of small flying vehicles and robots. It’s possible the propulsive mechanism sea butterflies use could lend an extra advantage to man-made devices in the future. More information on this research has been published in the Journal of Experimental Biology.
Via New Scientist
Images via Wikipedia