One of the most important skills in living in the ocean is swimming. Salmon is the swimmer of the ocean, and it swims like a swift torpedo. Using its strong muscles, salmon can sometimes even jump out of the water.
Compared with muscular salmon, the sea moon jellyfish is like a plastic bag drifting in the ocean, "weak, pitiful, and helpless". But surprisingly, a recent study showed that frail jellyfish exercise more efficiently than muscular salmon. Even compared to any other swimming animal, jellyfish can consume less energy and swim longer distances.
The secret lies in its fragile and transparent body. Compared to other swimming animals, the body of the sea moon jellyfish q bomb allows it to swim farther away with less energy.
In a study published in the Proceedings of the National Academy of Sciences, Brad Gemmell, a marine biologist in Massachusetts, said that the marine jellyfish has a unique way of swimming, which can recycle some of the energy consumed when swimming. In this way, the sea moon jellyfish can continue to advance in the water without expending energy during each swimming interval.
When the jellyfish swims, the swirling water vortex it produces gives it extra thrust. Image credit: brad gemmell
In order to study the unique swimming style of the sea moon jellyfish, gemmell used magnesium chloride reagent to paralyze the sea moon jellyfish and prevent the sea moon jellyfish from swimming on their own. A mechanical pusher is then used to push them forward to analyze the water flow around them.
Moon jellyfish swim by contracting the umbrella body. When the sea moon jellyfish shrinks the umbrella body, two circular water swirls are generated at the edge of the umbrella body, which looks like two "donuts". As the jellyfish umbrella body relaxes, the second "donut" rotates faster at the edge of the umbrella body and directs the water flow, forming a high-pressure area at the mouth of the jellyfish (the orange-red area in the picture below), which in turn provides the jellyfish with a second thrust. Through these "donut"-style vortexes, the sea moon jellyfish can continuously introduce water into the middle of its umbrella body and push itself forward.
A higher pressure area (reddish-orange area) is formed at the mouth and wrist of the sea moon jellyfish. Source: Brad Gemmell
In addition, the elastic umbrella body of the sea moon jellyfish can be automatically relaxed, which means that the second propulsion process does not require any additional energy. In this way, the sea moon jellyfish increased the swimming distance by 80% without expending energy.
Doesn't that sound tempting? Unfortunately, this "do more with less" approach is only suitable for low speeds and relatively small body sizes. Just like although glucose can provide energy most efficiently, human beings can't only eat glucose for a lifetime, they will have tooth decay.
However, the efficient swimming technique of the sea moon jellyfish can be applied to the design of ocean-going machines, such as buoys floating on the surface of the sea for a long time or underwater submersibles diving deep into the seabed. Gemmell said that by borrowing the swimming method of the sea moon jellyfish, these machines can be deployed for a longer period of time without additional energy or maintenance. And that could revolutionize ocean monitoring.
Who knows what kind of future this group of "love to run" jellyfish can "run"?
参考：nature--<why a jellyfish is the ocean's most efficient swimmer>
Written by: Zhang Shuling, Ni Zitai @ Hongjie played the piano