Suction Flows Generated by the Carnivorous Bladderwort Utricularia—Comparing Experiments with Mechanical and Mathematical Models

Abstract

Suction feeding is a well-understood feeding mode among macroscopic aquatic organisms. The little we know about small suction feeders from larval fish suggests that small suction feeders are not effective. Yet bladderworts, an aquatic carnivorous plant with microscopic underwater traps, have strong suction performances despite having the same mouth size as that of fish larvae. Previous experimental studies of bladderwort suction feeding have focused on the solid mechanics of the trap door’s opening mechanism rather than the mechanics of fluid flow. As flows are difficult to study in small suction feeders due to their small size and brief event durations, we combine flow visualization on bladderwort traps with measurements on a mechanical, dynamically scaled model of a suction feeder. We find that bladderwort traps generate flows that are more similar to the inertia-dominated flows of adult fish than the viscosity-dominated flows of larval fish. Our data further suggest that axial flow transects through suction flow fields, often used in biological studies to characterize suction flows, are less diagnostic of the relative contribution of inertia versus viscosity than transverse transects.

Bladderworts, the smallest known suction feeders, generate inertia‐dominated flows to capture prey

“…We recorded 24 suction events for 15 traps of Utricularia gibba (data published in validation of a mechanical model, (Singh et al ., 2020)) and 11 traps of Utricularia australis using PIV to characterise the flow outside the trap (Fig. 1; Table S2), and 14 suction events for 14 traps of U. gibba using particle tracking to characterise the flow inside the channel (Fig.…”

“…(e) Flow speed sampled along a semicircular transect as indicated in (a). Lines show model predictions by a creeping‐flow model (Sampson, 1891) and a mechanical model simulating the flow of a bladderwort trap (Singh et al ., 2020) to facilitate comparison, the speed axis of each model curve has been scaled to yield the same flux into the hemispherical cap as calculated from the bladderwort data. (f) Axial transect measurements from 24 traps (points), with distance z scaled by the gape diameter d and speed u normalised to speed at the half‐gape point u d /2 .…”

“…Linearised Navier–Stokes equations have been developed for undeveloped steady‐state flow at a circular pipe entrance (Langhaar, 1942). These solutions have been implemented in commercial software (Wolfram Mathematica) (Berg et al ., 2020; Singh et al ., 2020); the energy balance as a function of speed could be solved with the integral values as given (Berg et al ., 2019). To solve for speed as a function of pressure drop the roots of the energy balance were found numerically.…”

Experimental Study on the Adoption of Flushing Technique in Successive Alkalinity-Producing Systems with a Focus on Influence Radius of Orifice

“…This is because if the magnitude of the ow velocity around the ori ce is large enough to move the sediment, the sediment can escape out of the pipe with the water, and if the velocity is small, the sediment remains stationary. Singh et al (2020) studied the ow phenomenon that occurs when a pipe sucks in the surrounding uid, which is similar to the phenomenon of an ori ce sucking water in a limestone bed. They presented the velocity distribution when a small pipe sucks in the surrounding uid, as shown in Fig.…”

A Tunable, Simplified Model for Biological Latch Mediated Spring Actuated Systems

“…Models have been developed to understand the extreme biomechanics of latch-mediated spring actuated organisms. Organism-specific models, including both continuum mechanics-based models (2)(3)(4)(5)(6)(7)(8)(9)(10) and physical modeling with biomimetic devices (2,(10)(11)(12)(13)(14), have been used to test hypotheses about the mechanisms of movement in specific organisms (Table 1 summarizes examples of recent work).…”