Seen as a light-colored plume, water jets out from the back of a larval dragonfly. Credit: Chris Roh and Mory Gharib/Caltech - Seen as a light-colored plume, water jets out from the back of a larval dragonfly.
A new understanding of the mechanics of dragonfly larvae respiration and maneuvering could lead to the next generation of prosthetic heart valves, say Caltech engineers. Mory Gharib (PhD '83), the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering in the Division of Engineering and Applied Science, and postdoctoral researcher Chris Roh (MS '13, PhD '17) studied Anisopteran dragonfly larvae, which live in water and both breathe and move by inhaling water, extracting oxygen from it, and then expelling the water back out through a tri-leaflet anal valve that is surprisingly similar in structure to tricuspid human heart valves. The larvae are able to control the retraction of each of the three leaves individually, and this, Gharib and Roh discovered, gives them fine control over the size and symmetry (or asymmetry) of the valve opening. "The dragonfly larva is the only insect that uses jet propulsion to move and the only arthropod known to use reciprocal jetting-inhaling and exhaling through the same orifice-for underwater breathing," says Roh, the lead author of a paper on the larval jets that was published online by the journal Bioinspiration & Biomimetics on May 30. To observe how the larvae directed the flow of water using the leaves on their anal valves, Gharib and Roh set up high-speed cameras around an aquarium filled with a colored dye and tethered 96 dragonfly larvae-one at a time-in front of the cameras using dental wax. They found that when the larvae retracted all three leaves, the water jet flows straight out, pushing the animals straight forward.
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