Regensburg 2022 – scientific programme
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BP: Fachverband Biologische Physik
BP 14: Active Matter 3 (joint session BP/CPP/DY)
BP 14.6: Talk
Wednesday, September 7, 2022, 11:00–11:15, H16
Rheotaxis of the ciliate — •Takuya Ohmura1, Yukinori Nishigami2, and Masatoshi Ichikawa3 — 1Biozentrum, University of Basel, Switzerland — 2Research Institute for Electronic Science, Hokkaido University, Japan — 3Department of Physics, Kyoto University, Japan
Rheotaxis, a property of organisms to move against an external flow, has a crucial role to stay in living environment. For instance, freshwater fishes in rivers swim upstream to avoid being swept away to the sea. Interestingly, recent studies reported that not only fish but also swimming cells show rheotaxis. We elucidated the rheotaxis of the ciliate, Tetrahymena, a well-known single-celled freshwater microorganism swimming by cilia [1]. While that microorganism doesn*t have a sensor to detect flow direction and micrometer-sized particles are swept away downstream in a viscous flow, what dynamics underlie the rheotaxis of the ciliate? Our experiments revealed that the ciliate slid upstream along a wall, which indicates that the cells receive rotational torque from shear flow to align swimming orientation. To evaluate the shear torque, we performed a numerical simulation with a hydrodynamic model swimmer adopting cilia dynamics in a shear flow. The result suggests that the ciliate automatically slides upstream by using cilia-stalling mechanics.
[1] T. Ohmura, et al., Science Advances, 7(43), eabi5878 (2021).