Pulsing prosthetic gives jellyfish super speed

Engineers in the US have used a small pulsing prosthetic device that directs jellyfish to swim at up to three times their normal speed.

Acting like a pacemaker, the prosthetic encourages jellyfish to speed up their natural pulsing motion, which they use to move through the oceans and capture prey. Typically, this motion sees the creatures move at around 2cm per second. With the device attached, that speed increases to between 4cm and 6cm per second.

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Measuring around 2cm in diameter, the microelectronic prosthetic is naturally buoyant and attaches to the animals via a small wooden barb. Once removed, the jellyfish return to their normal swimming speed and the researchers claim that the process does not appear to cause stress to the creatures. It is hoped that the bionic jellyfish could one day be used to help in ocean exploration. The research is published in Science Advances.

"We've shown that they're capable of moving much faster than they normally do, without an undue cost on their metabolism," said Stanford graduate student Nicole Xu, co-author of the study. "This reveals that jellyfish possess an untapped ability for faster, more efficient swimming. They just don't usually have a reason to do so."

In addition to making the jellyfish faster, the electrical jolts also made them swim more efficiently. Although the jellyfish swam three times faster than their usual pace, they used just twice as much energy to do so, as measured by the amount of oxygen consumed by the animals while swimming. This combination of speed and efficiency opens up the possibility of using jellyfish to help gather data from across the world’s oceans.

"Only a small fraction of the ocean has been explored, so we want to take advantage of the fact that jellyfish are everywhere already to make a leap from ship-based measurements, which are limited in number due to their high cost," said research lead John Dabiri, Professor of Aeronautics and Mechanical Engineering at Caltech.

"If we can find a way to direct these jellyfish and also equip them with sensors to track things like ocean temperature, salinity, oxygen levels, and so on, we could create a truly global ocean network where each of the jellyfish robots costs a few dollars to instrument and feeds themselves energy from prey already in the ocean."

Currently, the prosthetic can direct jellyfish to start swimming and control its pace. The next step will be to develop a system that guides them in specific directions and allows them to respond to signals from onboard sensors, according to Dabiri, who hopes to develop even smaller electronic controls that could be completely embedded in the animal's tissue.