Jellyfish have been using the same pulsing motion to swim for millions of years, and new research reveals what makes this age-old technique so efficient.
A team of researchers used mathematical models to demonstrate how jellyfish and lampreys move through the water with an efficiency not seen in any other marine creature, Stanford University reported.
"It confounds all our assumptions," said John Dabiri, a professor of civil and environmental engineering and of mechanical engineering at Stanford. "But our experiments show that jellyfish and lampreys actually suck water toward themselves to move forward instead of pushing against the water behind them, as had been previously supposed."
The findings showed that as lampreys move through the water, they create a pocket of low-pressure water inside every bend of its body. Water ahead of the animal moves into these pockets, pulling the lamprey forward. Jellyfish swim in a similar fashion, using the collapse of their umbrella-shaped plume to pull water in from ahead and propel them forward. The new findings could help scientists achieve significant advances in the field of underwater vehicles.
"For nearly 100 years, it has been assumed that mimicking natural swimming meant finding ways to generate high pressures to push water backward for thrust," Dabiri said. "Now we realize we've had it backward, and so the search is on for ways to generate low-pressure suction to achieve more efficient underwater propulsion."
The findings could also shed light on evolutionary phenomena that allowed these efficient swimming methods to develop.
"Animals that move in fluids almost invariably use flexible, rather than rigid, propulsive structures. This work opens the door to understanding why evolution has converged upon particular bending patterns," said jellyfish expert John Costello of Providence College.
The findings were published in a recent edition of the journal Nature Communications.
