Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session P02: Invited Talk: Ciliary fluid dynamics of swimming, feeding, pumping, and sensing |
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Chair: Petia Vlahovska, Northwestern University Room: Hall 2 |
Monday, November 25, 2024 11:45AM - 12:20PM |
P02.00001: Ciliary fluid dynamics of swimming, feeding, pumping, and sensing Invited Speaker: Takuji Ishikawa Cilia are cell organelles acquired by eukaryotes more than a billion years ago that induce flow in the surrounding fluid by periodically beating in waves. Many eukaryotes, from microorganisms to humans, possess cilia. From the viewpoint of biofluid mechanics, cilia perform four major functions: swimming, feeding, pumping, and sensing. In this talk, I will explain the flow produced by cilia and its biological functions. First, the swimming speed and efficiency of ciliary swimming are discussed. It is shown that the friction between cilia and the cell surface is extremely large. Our analysis reveals that swimming efficiency is highest when the number of cilia increases in proportion to the square of the body length. The relationship of microorganisms in nature was also found to be a square relationship, suggesting that they may have survived by attaining optimal efficiency. Next, the swimming and feeding of the colony of choanoflagellate are discussed. The choanoflagellates turn their flagella inward when exposed to light and flip their flagella outward when it is dark. Why they behave this way is an interesting question. Our analysis illustrates that the inward flagellar flow is advantageous for feeding, while the outward flagellar flow is advantageous for swimming. It is amazing that microorganisms are able to adapt to their environment by altering their ciliary flow. Finally, I introduce nodal flow in mouse embryos, the direction of which determines the left-right axis of the body. Our analysis suggests that the direction of flow generated by the motile cilia must be sensed by the immotile cilia located at the edge of the nodal cavity. Further experimental investigations proved our hypothesis and found that cilia can sense not only the intensity but also the direction of flow. These studies illustrate that ciliary flow can generate a variety of biological functions and its importance in our lives. |
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