Scientists discovered a colonial jellyfish-like species that has an unusual way of moving around.
Many marine animals use jet propulsion to navigate their environments, but it is extremely rare to see an entire colony of animals coordinate multiple jets for "whole-group" locomotion, the Marine Biological Laboratory reported. New research suggests the species Nanomia bijuga uses a multi-jet propulsion system based on a sophisticated division of labor between young and old members of the community.
"This is a highly efficient system in which no developmental stage is wasted," said lead author John H. Costello of Providence College, an Adjunct Scientist and Whitman Center Investigator at the Marine Biological Laboratory (MBL) in Woods Hole.
In this system, the younger members of the group are positioned at the leading end of the colony, where they use their small jets for turning and steering; the older members use their larger jets to propel the group from the back. The jet-producing members of the physonect colony (nectophores) are genetically identical clones arranged in a propulsive unit, called a nectosome. These clones can move the equivalent of a human running an entire marathon every day while dragging the equivalent of their body mass behind them.
To make their findings, the researchers set up video cameras off Friday Harbor, Washington. They used these videos to analyze particle movement around the Nanomia group to reveal the size and power of individual jets, as well as their angle in relation to the individual animals. They determined the youngest members of the group had the lowest jet propulsion power, but have a big effect on the position of the unit.
"The young members have what we call a long lever arm," Costello said. "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."
The researchers believe the incredible system could help inspire future designs of underwater distributed-propulsion vehicles.
The findings were published in a recent edition of the journal Nature Communications.
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