Reorganisation of complex ciliary flows around regeneratingStentor coeruleus

Abstract

20The phenomenon of ciliary coordination has garnered increasing attention in recent decades, with multiple 21 theories accounting for its emergence in different contexts. The heterotrich ciliate Stentor coeruleus is a 22unicellular organism which boasts a number of features which present unrivalled opportunities for 23 biophysical studies of cilia coordination. With their cerulean colour and distinctive morphology, these large 24protists possess a characteristic differentiation between cortical rows of short body cilia used for swimming, 25and an anterior ring structure of fused oral cilia forming a membranellar band. The oral cilia beat 26 metachronously to produce strong feeding currents. In addition to this complex body plan, Stentor have 27 remarkable regenerative capabilities. Minute fragments of single cells can over the period of hours or days, 28 regenerate independently into new, proportional individuals. Certain environmental perturbations elicit a 29 unique programmed response known as oral regeneration wherein only the membranellar band is shed and 30 a new, ciliated oral primordium formed on the side of the body. Here, we target oral regeneration induced by 31sucrose-shock to reveal the complex interplay between ciliary restructuring and hydrodynamics in Stentor, 32which accompanies the complete developmental sequence from band formation, elongation, curling, and 33 migration toward the cell anterior. 34 35

Origins of eukaryotic excitability

“…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).…”

Ciliary propulsion and metachronal coordination in reef coral larvae

“…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).…”

“…In the stroke direction, steric interactions promote in-phase synchronization since interciliary spacing is so small (0.1 L ); 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.…”

Ciliate Biology: The Graceful Hunt of a Shape-Shifting Predator

“…After all, the assignment of 'head' and 'body' is a somewhat anthropomorphic notion. In Lacrymaria, and in many other ciliates, the head, which contains the oral apparatus, can be removed and regenerated [15]. Reputedly, ''detached heads'' can ''do everything except the backward movement'' [1].…”