Many marine species use jet propulsion to swim including jellyfish and squids, but Nanomia bijuga uses not only jet propulsion but also coordinated work from its peers within a colony to move around.
Until recently, researchers didn’t notice what happened within a colony of Nanomia bijuga, but a recent study revealed that colony members are active swimmers that coordinate their moves to the benefit of the entire group.
The study was published recently in the journal Nature Communications.
The multi-jet propulsion techniques of Nanomia may help engineers design distributed-propulsion vehicles that can be employed underwater.
John H. Costello, lead author of the findings and researcher at Providence College in Providence, Rhode Island, said that the colony forms a highly efficient system in which no thrust power goes to waste.
He explained that even the little ones use their small jets to help the colony move forward and steer, while the old ones stay in the back and provide powerful thrust whenever the colony wants to go to surface.
“It’s a quite sophisticated design, for what would seem like a simple arrangement,”
N. bijuga thrives only in colonies and it is a distant cousin of corals and jellyfish. It usually feeds on plankton, but it needs to reach surface for that. Nevertheless, to avoid predators, N. bijuga goes to ocean surface during nighttime and returns to the depths in dawn.
In the upper part of the colony there is a group of genetically identical twins called nectophores which generate the jet for the entire colony. Nectophores act like a single unit called nectosome and they tow behind them feeding and reproduction units up to 200 meters every day.
Scientists were able to observe how the colony used jet propulsion to move by recording their moves and using image analysis techniques to see how the water was pushed out around the moving colony.
Interestingly, the young members of the colony had a great impact on the group although their jet power was weak. The small ones were positioned at the top of the nectosome and far from the edge where the nectosome connects with the rest of the colony, so their small but directed force could easily steer the entire colony.
Costello likened the young members of the colony to a door handle. When you try to open a door by pushing near its hinges it is very difficult. But when you use the door handle which is located far from the hinges you can open it easily.
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