Entrapment of Ciliates at the Water-Air Interface

Ferracci, Jonathan; Ueno, Hironori; Numayama-Tsuruta, Keiko; Imai, Yohsuke; Yamaguchi, Takami; Ishikawa, Takuji

doi:10.1371/journal.pone.0075238

Cited by 26 publications

(23 citation statements)

References 22 publications

(18 reference statements)

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“…In terms of scattering when stable near surface swimming does not occur, the most extensive difference was in the extent of surface residence, though a reduction in the level of scattering was also observed. These observations can be concisely understood in terms of the reduced amount of shear and thus viscous torque near the free-surface boundary compared to the no-slip scenario [53].…”

Section: Discussionmentioning

confidence: 93%

Squirmer dynamics near a boundary

2013

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The boundary behavior of axisymmetric microswimming squirmers is theoretically explored within an inertialess Newtonian fluid for a no-slip interface and also a free surface in the small capillary number limit, preventing leading-order surface deformation. Such squirmers are commonly presented as abridged models of ciliates, colonial algae, and Janus particles and we investigate the case of low-mode axisymmetric tangential surface deformations with, in addition, the consideration of a rotlet dipole to represent torque-motor swimmers such as flagellated bacteria. The resulting boundary dynamics reduces to a phase plane in the angle of attack and distance from the boundary, with a simplifying time-reversal duality. Stable swimming adjacent to a no-slip boundary is demonstrated via the presence of stable fixed points and, more generally, all types of fixed points as well as stable and unstable limit cycles occur adjacent to a no-slip boundary with variations in the tangential deformations. Nonetheless, there are constraints on swimmer behavior-for instance, swimmers characterized as pushers are never observed to exhibit stable limit cycles. All such generalities for no-slip boundaries are consistent with observations and more geometrically faithful simulations to date, suggesting the tangential squirmer is a relatively simple framework to enable predications and classifications for the complexities associated with axisymmetric boundary swimming. However, in the presence of a free surface, with asymptotically small capillary number, and thus negligible leading-order surface deformation, no stable surface swimming is predicted across the parameter space considered. While this is in contrast to experimental observations, for example, the free-surface accumulation of sterlet sperm, extensive surfactants are present, most likely invalidating the low capillary number assumption. In turn, this suggests the necessity of surface deformation for stable free-surface three-dimensional finite-size microswimming, as previously highlighted in a two-dimensional mathematical study of singularity swimmers [Crowdy et al., J. Fluid Mech. 681, 24 (2011)].

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Section: Discussionmentioning

confidence: 93%

Squirmer dynamics near a boundary

2013

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“…Motion of a two-dimensional (2-D) treadmilling swimmer near a plane wall was analysed theoretically, with the observation of nonlinear periodic swimming orbits (Crowdy & Or 2010;Crowdy 2011). Also, Ferracci et al (2013) observed the trapping of fresh water ciliates (Tetrahymena thermophila) near a water-air interface.…”

Section: Introductionmentioning

confidence: 99%

Motion of a model swimmer near a weakly deforming interface

Shaik

Ardekani

2017

J. Fluid Mech.

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Locomotion of microswimmers near an interface has attracted recent attention and has several applications related to synthetic swimmers and microorganisms. In this work, we study the motion of a model swimmer called the ‘squirmer’ with an arbitrary time-dependent swimming gait near a weakly deforming interface. We first obtain an exact solution of the governing equations for the motion of the swimmer near a plane interface using the bipolar coordinate method, and then an approximate solution using the method of reflections. We thereby derive the velocity of a swimmer due to small interface deformations using the domain perturbation method and Lorentz reciprocal theorem. We use our solution to study the dynamics of a swimmer with steady, as well as time-reversible, squirming gaits. The long-time dynamics of a time-reversible swimmer is such that it either moves towards or away from the interface. Thus, we divide its phase space into regions of attraction (repulsion) towards (from) the interface. The long-time orientation of a time-reversible swimmer that is moving towards the interface depends on its initial orientation. Additionally, we find that the method of reflections is accurate to $O(1)$ distances of the swimmer from the interface.

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“…Ciliates have a large number of hair-like organelles, termed cilia, that beat around the whole body to induce thrust force. While the remarkable activity of ciliates is usually observed in bulk water ( 11 – 15 ), they frequently accumulate on air/fluid and solid/fluid interfaces in nature ( 16 – 20 ). Although these two major characteristics (i.e., sliding on surfaces and traveling rapidly in bulk water) are commonly recognized as instinctive behaviors, the mechanism of the sliding motion remains unclear.…”

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confidence: 99%

“…Puller swimmers, which are driven by anterior flagella (e.g., Chlamydomonas ), have been numerically analyzed to determine their attractive motions toward a wall. Finally, the neutral swimmer is used as a model for ciliates that represent a uniform driving force covering the swimmer surface, assuming that cilia are beating all over the cell surface, as in Volvox ( 32 ) and Tetrahymena ( 33 ). The trajectories of neutral swimmers near a wall have been analytically and numerically reported.…”

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confidence: 99%

Simple mechanosense and response of cilia motion reveal the intrinsic habits of ciliates

Ohmura

Nishigami

Taniguchi

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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SignificanceSingle-celled microorganisms are important in ecosystems, and their behaviors impact the Earth’s environments. To survive in harsh environments, these organisms frequently act as though exercising discretion. How do they achieve such intelligent behaviors? In this work, we focused on the accumulation of ciliates on solid/fluid interfaces, where they can obtain sufficient nutrients and a stable environment. This phenomenon is not described in the standard hydrodynamics of microswimmers. Our experiment and simulation revealed that simple principles, the anisotropic shape of the cell and the mechanosensing nature of cilia, induce the accumulation of ciliates on solid/fluid interfaces. The contribution of our work is that a simple response of the cellular apparatus and fluid dynamics explain the apparently clever behavior of ciliates.

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Entrapment of Ciliates at the Water-Air Interface

Cited by 26 publications

References 22 publications

Squirmer dynamics near a boundary

Squirmer dynamics near a boundary

Motion of a model swimmer near a weakly deforming interface

Simple mechanosense and response of cilia motion reveal the intrinsic habits of ciliates

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