USF Biologist Discovers Secret to Highly Efficient Swimming in Certain Animals, Such as Jellyfish

Previous studies have shown that jellyfish and eels can move using very low amounts of energy that would make a Toyota Prius jealous. In fact, these ocean denizens can go from point A to point B using less energy than any other swimmer, runner or flier ever measured. However the secret behind such amazing energetic efficiency has remained a mystery, until now. A team of scientists led by Dr. Brad Gemmell, an assistant professor in the University of South Florida’s Department of Integrative Biology, has revealed that these marine animals do something completely unexpected when they swim.

According to the research team, comprised of scientists from five institutions, understanding how animals move is essential to understanding their evolutionary history, their fitness and their ecological impact. Understanding how animals move so efficiently through water is also important to engineers who study bio-inspired design and take ideas from nature to make more efficient underwater vehicles. Experiments carried out to better understand the locomotion used by free-swimming jellyfish and lampreys, eel-like animals that move with undulating, wave-like body motions, has revealed that these animals move forward not by pushing against the water, but by sucking the water toward them.

“Until now, it has been widely assumed in the literature and the text books that animals swim primarily by pushing against the fluid to generate high pressure and move the animal forward,” said Gemmell. “However, it turns out that at least with some of the most energetically efficient swimmers, low pressure dominates and allows these animals to pull themselves forward with suction.Given our findings, we may have to rethink our ideas about some of the evolutionary adaptations acquired by swimming animals and how we approach vehicle design in the future.”

Their recent experiments, recounted in a paper just published in Nature Communication, aimed at better understanding lamprey and jellyfish locomotion by observing lampreys swimming through a tank of water containing tiny glass beads that were illuminated with a laser. The animals’ swimming motion perturbed the beads in such a way as to enable visualization of the flow and timing of glass bead movement in concert with the lampreys’ movements. Using high speed digital cameras that recorded movement in fractions of a second, the scientists were able to directly measure the ‘hydrodynamic efficiency’ of their swimming process.