A species of sea snail, aptly known as the Sea butterfly, flaps its wings to produce lift and propel itself though the water.
Georgia Institute of Technology researchers went to the Pacific Ocean to scoop up hundreds of the 3mm marine molluscs (pteropods) and then used high-speed cameras to watch how they move. They found that Sea butterflies Limacina helicina, don’t paddle like most small water animals. Instead, they flap their wings in a way more reminiscent of flying insects (scroll down for video).
"Snails evolutionarily diverged from flying insects 550 million years ago," said Donald Webster, a professor in Georgia Tech’s School of Civil and Environmental Engineering. "Hence, it is amazing that marine snails are using the same figure-eight wing pattern that is typical of their very distant airborne relatives."
Another amazing similarity between the pteropods and insects is the use of a clap-and-fling wing motion. Each species claps its wings together, then rapidly flings them apart to generate enhanced lift.
"Almost all other plankton use their appendages as paddles, kind of like a turtle," said David Murphy, who led the study. "Sea butterflies are honorary insects."
The team did find one major difference in sea butterflies and flying insects. Nearly two-thirds of the plankton’s body is its shell. When it’s not moving forward, it sinks to the ocean floor. To avoid sinking, the pteropod rotates its body up to 60 degrees with each stroke. The rotation puts its wings in the proper position to flap downward during every half-stroke (about 10 times per second) and move in an upward, zig-zag path in the water.
"Insects and birds don’t typically rotate their bodies in a similar manner to generate lift," said Webster. "By rotating their shell during each stroke, sea butterflies put their wings in a position to always generate upward thrust and fly forward."
You can watch these unusual animals in motion in the video below.