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Hydrodynamics of the bladderwort feeding strike
Otto Berg1, Matthew D Brown2, M Janneke Schwaner3
1Department of Chemistry, California State University, Fresno, California.
Summary
The bladderwort Utricularia gibba uses suction feeding in its tiny traps, achieving high speeds efficiently. This mechanism has a minimum size limit due to fluid dynamics and friction.
Area of Science:
- Fluid dynamics
- Biophysics
- Plant biology
Background:
- The aquatic bladderwort Utricularia gibba employs unique suction traps to capture zooplankton.
- These traps, less than 1 mm in size, operate via suction, a mechanism typically ineffective at such small scales (creeping-flow regime).
Purpose of the Study:
- To investigate the adaptations enabling suction feeding in Utricularia gibba's micro-scale traps.
- To understand the fluid dynamics governing the suction feeding mechanism at small scales.
Main Methods:
- Measured internal flow speeds during artificially triggered feeding strikes without prey.
- Compared experimental data with analytical models: inviscid time-dependent Bernoulli equation and a steady-state model with friction.
Main Results:
- Initial suction dynamics align with a time-dependent Bernoulli equation, with maximum flow speed dependent on pressure difference.
- High initial acceleration is influenced by pressure difference and channel length.
- The short duration and channel length result in an undeveloped viscous steady state, with only 17% power loss to friction.
Conclusions:
- Utricularia gibba's suction feeding mechanism is highly efficient at micro-scales.
- Decreasing channel diameter rapidly reduces energy efficiency and fluid speed, establishing a lower limit for bladderwort trap size.
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