Feeding of attached and swimming ciliates achieve hydrodynamic equivalence
Flow physics imposes no constraint on the feeding rates that are achievable by the swimming versus sessile strategies – they can both be equally competitive in transporting nutrients and wastes. The evolutionary pressures that shaped “swim” and “stay” strategies acted in concert with, not against, flow physics.
Optimal feeding of attached ciliates depends on Péclet number
Concentration and flow field around a sessile ciliate corresponding to cilia beating in the first (left) and the second (right) mode. Colormap: concentration field, from 0% (light ) to 100%(dark) of concentration background. Arrows: streamlines of flow field.
Under low Péclet number conditions, optimal feeding occurs via a ‘treadmill’ motion of surface cilia, regardless of the organism’s mobility. However, at high Péclet numbers, a symmetric dipolar surface velocity that keeps the organism stationary achieves near-optimal feeding performance for swimming ciliates and serves as an optimal solution for attached ciliates [2].
Feeding in non-uniform concentration field
Cross section of a 3D simulation of nutrients concentration evolution surrounding a sessile model ciliate feeding in a non-uniform concentration field. Surface motion and feeding follow horizontal axis-symmetry. Initial concentration field has a constant concentration gradient with higher on the right. Two concentration contour lines are at concentration level 20% (solid line), and at level 120% (dash line).
Cilia-driven flow in spherical confinement
The study of cilia-driven flow extends in embryo development, where the emergence of asymmetry is closely linked to the subsequent formation of asymmetric organs and morphological structures. Symmetry-breaking events, facilitated by ciliary-directed fluid flow, are observed across various species, including mice, Xenopus, zebrafish, among others. My interest lies in understanding of cilia function in the directional flow formation and exploring the robustness of flow patterns generated during biological development, where stochastic processes are inherent.
Reference
- Liu, J., Man, Y., Costello, J. H., & Kanso, E. (2024). Feeding Rates in Sessile versus Motile Ciliates are Hydrodynamically Equivalent. eLife, 13.
- Liu, J., Man, Y., Costello, J. H., & Kanso, E. (2024). Optimal Feeding of Swimming and Attached Ciliates. arXiv preprint arXiv:2404.13467.