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Published December 6, 2022 | Published + Supplemental Material
Journal Article Open

Distributed propulsion enables fast and efficient swimming modes in physonect siphonophores


Many fishes employ distinct swimming modes for routine swimming and predator escape. These steady and escape swimming modes are characterized by dramatically differing body kinematics that lead to context-adaptive differences in swimming performance. Physonect siphonophores, such as Nanomia bijuga, are colonial cnidarians that produce multiple jets for propulsion using swimming subunits called nectophores. Physonect siphonophores employ distinct routine and steady escape behaviors but–in contrast to fishes–do so using a decentralized propulsion system that allows them to alter the timing of thrust production, producing thrust either synchronously (simultaneously) for escape swimming or asynchronously (in sequence) for routine swimming. The swimming performance of these two swimming modes has not been investigated in siphonophores. In this study, we compare the performances of asynchronous and synchronous swimming in N. bijuga over a range of colony lengths (i.e., numbers of nectophores) by combining experimentally derived swimming parameters with a mechanistic swimming model. We show that synchronous swimming produces higher mean swimming speeds and greater accelerations at the expense of higher costs of transport. High speeds and accelerations during synchronous swimming aid in escaping predators, whereas low energy consumption during asynchronous swimming may benefit N. bijuga during vertical migrations over hundreds of meters depth. Our results also suggest that when designing underwater vehicles with multiple propulsors, varying the timing of thrust production could provide distinct modes directed toward speed, efficiency, or acceleration.

Additional Information

© 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). Kayla Nease assisted with video analyses. Matt K. Fu and Alejandro Damian-Serrano provided useful comments on the manuscript. Caitlyn Webster provided the illustration for Fig. 1A. Funding was provided by the Gordon and Betty Moore Foundation (8835) and the National Science Foundation awarded to SPC (2100156 and 2114169) and JHC (2100705 and 2114170) and BJG (2100703). Author contributions: K.T.D. and K.R.S. designed research; K.T.D., B.J.G., S.P.C., J.H.C., and K.R.S. performed research; K.T.D. and J.O.D. contributed new reagents/analytic tools; K.T.D. analyzed data; and K.T.D. wrote the paper. The authors declare no competing interest.

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Published - pnas.2202494119.pdf

Supplemental Material - pnas.2202494119.sapp.pdf


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August 22, 2023
October 23, 2023