The sea butterfly, or Limacina helicina, is a zooplankton snail that lives in cold oceans.
The sea butterfly (Limacina helicina), a zooplankton snail that lives in cold oceans, truly lives up to its name. Georgia Tech researchers went to the Pacific Ocean to scoop up hundreds of the 3-millimeter marine mollusks and then used high-speed cameras to watch how they move. They found that sea butterflies don’t paddle like most small water animals. Instead, they’re like flying insects, flapping their wings to propel themselves through the water.
“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 these 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.
The team did find one major difference between 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), thereby enabling it to move in an upward, zig-zag path through the water.
The research was reported in The Journal of Experimental Biology. — Jason Maderer