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![(a) Schematic of a single Stentor with key morphological features highlighted. The membranellar band [8] comprises rows of oral cilia arranged in parallel stacks (each approx. 7.5 µm × 1.5 µm). (b) Confocal immunofluorescence images highlighting the structure and organization of the membranellar band (MB), cortical striation patterns and associated rows of short body cilia. Note the abrupt change in width at the locus of stripe contrast (LSC). (c) Top view of the frontal field (FF) and gullet region (G). Antibody used in (b,c) was anti-α-tubulin (scalebars = 10 µm).](profile/Kirsty-Wan/publication/334062089/figure/fig1/AS:952283915370496@1604053586356/a-Schematic-of-a-single-Stentor-with-key-morphological-features-highlighted-The.png)
(a) Schematic of a single Stentor with key morphological features highlighted. The membranellar band [8] comprises rows of oral cilia arranged in parallel stacks (each approx. 7.5 µm × 1.5 µm). (b) Confocal immunofluorescence images highlighting the structure and organization of the membranellar band (MB), cortical striation patterns and associated rows of short body cilia. Note the abrupt change in width at the locus of stripe contrast (LSC). (c) Top view of the frontal field (FF) and gullet region (G). Antibody used in (b,c) was anti-α-tubulin (scalebars = 10 µm).
Source publication
The phenomenon of ciliary coordination has garnered increasing attention in recent decades, with multiple theories accounting for its emergence in different contexts. The heterotrich ciliate Stentor coeruleus is a unicellular organism which boasts a number of features which present unrivalled opportunities for biophysical studies of cilia coordinat...
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Context 1
... unicellular ciliates occur widely in both freshwater and marine habitats, and exhibit both free-swimming and sedentary characteristics depending on environmental circumstance. Individual cells undergo dynamic and extensive shape changes owing to a highly contractile cortical structure, assuming a pear or tear-drop shape when free-swimming, contracting into a ball when disturbed, or else extending up to 1 mm in a rest state in which cells become attached to substrates via a posterior holdfast ( figure 1a). ...
Context 2
... coeruleus, also called the Blue Stentor [7,9], was favoured historically for cytological studies owing to its large size and moniliform macronucleus [10] and has been the subject of recent genomic studies [11]. The conical surface of the organism bears longitudinal stripes of distinctive colouration extending from the anterior all the way down to the tapered holdfast ( figure 1a). The stripes have graded width around the cell; the region where stripe gradation becomes discontinuous is called the locus of stripe contrast (LSC), or 'ramifying zone'. ...
Context 3
... end of the MB terminates freely, while the other end spirals into a funnelshaped invagination or gullet. Comprising around 250 stacked membranelles, the entire MB encloses the frontal field (FF), which is distinguished by a change in stripe orientation ( figure 1c). The FF contains stripes that originated as ventral stripes that have migrated upwards over the course of regeneration (see §2). ...
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... body cilia (which do not undergo regeneration) remained motile but beat only intermittently throughout the oral regeneration process, and were capable of producing large-scale flows. We verified that the unsteady nature of body cilia activity also pertains to organisms that were not surfaceadhered (electronic supplementary material, figure S1). This unsteadiness could underlie switching between swimming and feeding states: a stroke pattern optimized for feeding may reduce swimming efficiency [29], or vice versa. ...
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... fully regenerated Stentor, the membranelles exhibit robust phase coordination and metachronal waves (MCW), the establishment of which is associated with a sharp transition to faster flows (on the order of 100 µm s −1 ) and with the appearance of the feeding vortex. Structurally similar flow fields were also measured in Stentor that have not been adhered to a substrate, but rather were attached spontaneously by their posterior holdfast (electronic supplementary material, figure S1). The morphology of these flow fields compares well with feeding flows around isolated Vorticella (a contractile, stalked ciliate that bears strong resemblance to Stentor) in the presence of a no-slip boundary [31,32]. ...
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... that are arranged randomly in the anarchic field, consistent with the lack of ciliary coordination that we have observed. Between 4 and 5 h post sucrose shock these cilia undergo restructuring to assemble into regularly stacked rows of membranelles, with fibrillar structures connecting neighbouring membranelles also appearing at this stage ( figure 1a, and fig. 32 from [8]). A rotation in direction of fluid pumping from longitudinal (with respect to the cell axis) to transverse (figure 2d,e) is fully consistent with the transition from a longitudinally directed beat pattern to a transversely directed beat [25]. We attribute the intermittent coordination between nearby membranelles observed at ...
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Protists appeared relatively early in evolution, about 1.8 billion years ago, soon after the first prokaryotic organisms. During this time period, most species developed a variety of behavioral, morphological, and physiological strategies intended to improve the ability to capture prey or to avoid predation. In this scenario, a key role was played...
Citations
... In this view, ciliary metachrony is clearly visible, and the wave propagates in the −e θ direction. The 2D (time-space) autocorrelation of image intensity along the ciliary array as a function of time is used to estimate MCW parameters [28] (Fig. 3h). Wavecrests appear as diagonal lines, whose spacing in κ and t give the wavelength and period respectively (Fig. 3h). ...
... In the stroke direction, steric interactions promote in-phase synchronization since interciliary spacing is so small (0.1L); in the transverse direction however, phase shifts help prevent collisions between closely-packed beating cilia [44]. From protists to humans, the organisation and patterning of cilia undergoes precise developmental control [28,45], so improved pumping efficiency due to diaplectic metachronism could be a key evolutionary driver for ciliary placement and basal-body orientation. ...
Larval dispersal is critical to the survival of coral reefs. As the only motile stage of the reproductive cycle, coral larvae choose a suitable location to settle and mature into adult corals. Here, we present the first detailed study of ciliary propulsion in the common stony reef coral Acropora millepora. Using high-speed, high-resolution imaging, particle image velocimetry, and electron microscopy, we reveal the arrangement of the densely packed cilia over the larval body surface, and their organisation into diaplectic (transversely propagating) metachronal waves. We resolve the individual-cilium's beat dynamics and compare the resultant flows with a computational model of a ciliary array, and show that this form of ciliary metachronism leads to near-maximal pumping efficiency.
... This means that while diffusion alone is sufficient to ensure prokaryotes are well-stirred, eukaryotes must have acquired alternate means of advecting flows. Cilia and flagella are often used to create large-scale flows (up to mm/s) for filter feeding, or for replenishing the local nutrient concentration around cells [302,303]. For a cell with length L, moving at speed U, the importance of advection over diffusion is captured by the Péclet number [302,304], the ratio between advective (L/U) and diffusive timescales (L 2 /D). ...
All living cells interact dynamically with a constantly changing world. Eukaryotes in particular, evolved radically new ways to sense and react to their environment. These advances enabled new and more complex forms of cellular behavior in eukaryotes, including directional movement, active feeding, mating, or responses to predation. But what are the key events and innovations during eukaryogenesis that made all of this possible? Here we describe the ancestral repertoire of eukaryotic excitability and discuss five major cellular innovations that enabled its evolutionary origin. The innovations include a vastly expanded repertoire of ion channels, endomembranes as intracellular capacitors, a flexible plasma membrane, the emergence of cilia and pseudopodia, and the relocation of chemiosmotic ATP synthesis to mitochondria that liberated the plasma membrane for more complex electrical signaling involved in sensing and reacting. We conjecture that together with an increase in cell size, these new forms of excitability greatly amplified the degrees of freedom associated with cellular responses, allowing eukaryotes to vastly outperform prokaryotes in terms of both speed and accuracy. This comprehensive new perspective on the evolution of excitability enriches our view of eukaryogenesis and emphasizes behaviour and sensing as major contributors to the success of eukaryotes.
Cilia and flagella are fundamental units of motion in cellular biology. These beating, hair-like organelles share a common basic structure but maintain widely varying functions in systems ranging from the isolated flagella of swimming algae to the dense ciliary carpets that pump fluid in the brains of mammals. Experiments and models have begun to elucidate the inner workings of single cilia as complex nonlinear oscillators, and the variety of hydrodynamical phenomena that result from beating dynamics. These results have shed light on complex locomotion strategies observed in single-celled microorganisms and collective phenomena observed in microbial suspensions. In animal systems, dense ciliary arrays exhibit a variety of emergent phenomena, including active filtration, noise robustness and metachronal waves. Surprising phenomena have been observed in neuronally controlled ciliary arrays, demonstrating the need for new physical models of cilia that include central control, defect dynamics and topology. We review the emergent physics of cilia across scales, starting from the microscale dynamics of single cilia, and then proceeding to microorganisms and animal systems.
