Jellyfish aren't known for their speed, but new research suggests they may be the most efficient "propulsors" in the ocean.
Even though the often underestimated jellyfish won't be winning a race anytime soon, they are able to swiftly multiply and overrun almost any aquatic habitat they can get their tentacles on, a Marine Biological Laboratory (MBL) news release reported.
"It seems counterintuitive," lead author Brad Gemmell, an MBL postdoctoral scientist with John Costello of Providence College and Sean Colin of Roger Williams University, said.
"Fish are visual hunters; they can detect prey from a distance and they have very good chemosensory capabilities. Jellyfish, by comparison, are seemingly poor predators. They need direct contact with their prey through their tentacles, to feed, and they aren't fast swimmers," he said.
The researchers found jellyfish are able to be so dominant because of the energy they save by swimming more leisurely than other aquatic species.
"A jellyfish expends far less energy getting from point A to point B," Gemmell said.
For every gram of food the cunning jellyfish eats, it can put more energy into its ocean population takeover.
The research team believes the creature's secret is the previously overlooked relaxation phase.
"The contraction phase is when the animal is moving the fastest," Gemmell said. "That is when you see these vortex rings [in the water] being ejected behind the animal." The relaxation phase was primarily thought to be a period of reset for the next contraction. However, the scientists discovered that, during relaxation, a second vortex ring comes up the underside of the animal and gives it a second locomotive boost."
The secondary vortex ring is responsible for about 30 percent of the distance the jellyfish travels with each gooey contraction.
It's a neat little trick they use. The animal is paused; it's not expending any additional energy, but it is still accelerating. They call this new locomotive mechanism "passive energy recapture," Gemmell said.
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