Hydrodynamics of the bladderwort feeding strike

Otto Berg, Matthew D. Brown, M. Janneke Schwaner, Maxwell R. Hall, Ulrike K. Müller

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The aquatic bladderwort Utricularia gibba captures zooplankton in mechanically triggered underwater traps. With characteristic dimensions <1 mm, the trapping structures are among the smallest known that work by suction—a mechanism that would not be effective in the creeping-flow regime. To understand the adaptations that make suction feeding possible on this small scale, we have measured internal flow speeds during artificially triggered feeding strikes in the absence of prey. These data are compared with complementary analytical models of the suction event: an inviscid model of the jet development in time and a steady-state model incorporating friction. The initial dynamics are well described by a time-dependent Bernoulli equation in which the action of the trap door is represented by a step increase in driving pressure. According to this model, the observed maximum flow speed (5.2 m/s) depends only on the pressure difference, whereas the initial acceleration (3 × 104 m/s2) is determined by pressure difference and channel length. Because the terminal speed is achieved quickly (~0.2 ms) and the channel is short, the remainder of the suction event (~2.0 ms) is effectively an undeveloped viscous steady state. The steady-state model predicts that only 17% of power is lost to friction. The energy efficiency and steady-state fluid speed decrease rapidly with decreasing channel diameter, setting a lower limit on practical bladderwort size.
Original languageEnglish
Pages (from-to)29-37
JournalJournal of Experimental Zoology Part A: Ecological and Integrative Physiology
Volume333
Issue number1
DOIs
Publication statusPublished - 1 Jan 2020
Externally publishedYes

Funding

We thank Johan van Leeuwen for the opportunity to present our research at this commemorative symposium for R McN Alexander as part of the 8th World Congress of Biomechanics. This study was supported by the National Science Foundation (NSF‐BIO‐IOS #1352130 to U. K. M.) and California State University, Fresno. We thank Johan van Leeuwen for the opportunity to present our research at this commemorative symposium for R McN Alexander as part of the 8th World Congress of Biomechanics. This study was supported by the National Science Foundation (NSF-BIO-IOS #1352130 to U. K. M.) and California State University, Fresno.

FundersFunder number
NSF-BIO-IOS
National Science Foundation1352130
California State University

    Fingerprint

    Dive into the research topics of 'Hydrodynamics of the bladderwort feeding strike'. Together they form a unique fingerprint.

    Cite this