A radically different swimming technique enables creatures like eels and jellyfish to be highly efficient swimmers, traveling from point A to point B while expending far less energy than any other type of aquatic creature ever measured, according to a new study.
Dr. Brad Gemmell, an assistant professor in the University of South Florida’s Department of Integrative Biology, and his colleagues conducted a series of experiments to find out how these creatures move using undulating, wave-like body motions. They discovered that eels and jellyfish do not push through the water, but instead pull it towards 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, lead author of a new Nature Communications paper detailing the findings.
“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,” he added.
Findings could benefit underwater vehicles, other technology
Understanding how eels and jellyfish move is essential for understanding their ecological impact and their evolutionary history, the study authors explained. Knowing how such creatures are able to move so efficiently through the water could also be beneficial to engineers, allowing them to adapt these biological traits to improve the efficiency of submersible vehicles.
As part of their experiments, Gemmell’s team observed eel-like creatures known as lampreys as they swam through a tank of water filled with tiny glass beads that were illuminated using a laser. Their movements perturbed the beads in such a way that the scientists were able to see the flow and timing of bead movement as it correlated with the lamprey movements.
Then they used high-speed digital cameras to measure the overall “hydrodynamic efficiency” of the swimming process, and found that when the lampreys undulated to swim, they made a pocket of low-pressure water inside every bend of their body. Doing so caused the water ahead of them to fill this pocket, and the motion of this in-flowing water caused them to be pulled forward.
While the body shape of jellyfish differs from that of lampreys, the authors said that both types of creatures used the same basic approach to swimming. The findings, Gemmell and his fellow researchers said, provide a new perspective to evolutionary adaptation and “functional ecology” while also presenting the opportunity to adapt these mechanisms for use in technology.
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Feature Image: Thinkstock
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