[VIDEO] Multi-Jet Swimming Machine: A Rare Marine Species

A rare colony of jellyfish-like species coordinates multiple jets in order to move the group as a whole, according to a recent study. This species, identified by researchers as Nanomia bijuga, divides the locomotive labor among its group members, with the younger one leading and steering and the older, larger ones providing force from the back to move the colony from the deep ocean to surface waters. Researchers who watched N. bijuga off of Friday Harbor on Washington's coast think this swimming style could help in the design of underwater vehicles with distributed propulsion. 

"This is a highly efficient system in which no developmental stage is wasted," John H. Costello, lead author from Providence College and one of those researchers, said in a news release. "It's a quite sophisticated design, for what would seem like a simple arrangement.

N. bijuga is related to jellyfish, anemones and corals. They hide in deeper, darker oceans during the day, but come to the surface at night to feed on plankton, according to the release. 

In order to observe this species' unique swimming technique, researchers videotaped the organisms, then used image analysis to determine the size and thrust of individual jets, according to the release.

Some of the members were found to be responsible for towing the others behind them. These individuals are known as the nectophores and are the jet-producing members of the colony. They make up a relatively small collective unit, behind which a larger reproductive and feeding group is attached. This species can travel up to 200 meters each day. 

The researchers also found that the younger members at the front pushed out the least amount of water with their jets, but their slightest movement can turn the whole colony. This helps the N. bijuya to quickly alter its course when needed. 

"The young members have what we call a long lever arm," Costello said in the release. "They are like the handle of a door. If you push on a door near its hinges--its axis of rotation--the door is hard to open. But if you push on the door handle, which is far from the axis of rotation, the door opens easily. A little force placed with a big lever arm has a big effect on turning."

As new members bud at the tip of the colony, older ones move towards the back, the release noted. 

The researchers explained that, "These patterns permit all members of the colony to make important contributions to the propulsion and maneuvering traits that are critical for the success of N. bijuya in its natural environment."

Their study was recently published in Nature Communications.              

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