September 1, 2015

Could tiny jellyfish propulsion drive design of new underwater craft?

(September 1, 2015)  The University of Oregon's Kelly Sutherland has seen the future of under-sea exploration by studying the swimming prowess of tiny jellyfish gathered from Puget Sound off Washington's San Juan Island.

In a paper with four colleagues in the Sept. 2 issue of the journal Nature Communications, Sutherland details how a tiny type of jellyfish — colonial siphonophores — swim rapidly by coordinating multiple water-shooting jets from separate but genetically identical units that make up the animal.

Information on the biomechanics of a living organism that uses such a coordinated system ought to inspire "a natural solution to multi-engine organization that may contribute to the expanding field of underwater-distributed propulsion vehicle design," the co-authors conclude in their paper.

"This is a very interesting system for studying propulsion, because these jellies have multiple swimming bells to use for propulsion," said Sutherland, a biologist with both the UO's Oregon Institute of Marine Biology in Charleston and the Robert D. Clark Honors College on the Eugene campus. "This is relatively rare in the animal kingdom. Most organisms that swim with propulsion do so with a single jet. These siphonophores can turn on a dime, and very rapidly."

The jellies studied are Nanomia bijuga. They are members of the phylum Cnidaria, whose members have specialized stinging cells that are used mainly for capturing prey.

N. bijuga rarely exceed two inches in length but with tentacles can extend to a foot long. Samples were collected — most often at night when their translucent bodies are easily seen with light over the dark water — with cups off the floating docks at the University of Washington's Friday Harbor Laboratories. Individual colonies contained from four to 12 jet-like structures known as nectophores.

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