Trypanosome Motion Represents an Adaptation to the Crowded Environment of the Vertebrate Bloodstream
Figure 5
The plane-rotational motion of directionally swimming trypanosomes.
(A) Bright-field images from a xyt-series acquired with 500 fps (Video S8). Each image shows the beginning of successive up- or down-strokes of the flagellar tip, meaning a new wave starts at the anterior end of the flagellum every two images, i.e. after 28 frames. At each point in time, 2–3 wave crests are visible progressing from the anterior (tip of flagellum) towards the posterior part of the swimming cell. Every single up- and down-stroke causes forward motion in the opposite direction of wave propagation, seen as discrete translocations of about 0.7 µm, due to the helical path of the body and rotation of the cell body by about 25 degrees counter-clockwise. The cell was swimming at a speed of 25 µm s−1 and travelled 9.2 µm in 364 ms. In this period the flagellum produced 6.5 beats. (B) Illustration of the plane-rotational mode of motion compared to a bihelical mode (14). The latter requires a reversal of the rotational motion of the cell body after a turn of 180 degrees (marked by red asterisk), while the plane-rotational motion results in a continuous rotation in the same direction. Although the overall impression of these models appears rather similar, the physics underlying these two types of motion are fundamentally different.