Flagellates are unicellular organisms that use long, slender appendages (flagella) to create flows that propel them, support their nutrient and prey uptake, but also expose them to flow-sensing predators.
We present an analytical hydrodynamics model that represents the cell as a solid sphere and the flagellar beat as a number of steady or time-varying forces on the water. We show that in a breast-stroke swimming mode with two symmetrically arranged flagella, not only the backwards pointing power stroke, but also the concomitant transversal strokes contribute to propulsion. For an organism with both a longitudinal and a transversal flagellum (figure) we find the trajectory to be helical, the shape of which can be tuned by adjusting the forces produced by the two flagella relative to each other. The transversal flagellum can lead to strong feeding currents to localized capture sites on the cell surface. The model is especially useful for the investigation of prey and nutrient uptake on the cell for different flagellar arrangements and beat patterns due to its generality and adequate representation of the flow close to the cell surface.
Read the paper here.
Julia Dölger, Tomas Bohr and Anders Andersen. An analytical model of flagellate hydrodynamics. Physica Scripta 92, 044003 (2017)