High-speed microscopic imaging of flagella motility and swimming in Giardia lamblia trophozoites.

We report, in this paper, several findings about the swimming and attachment mechanisms of Giardia lamblia trophozoites. These data were collected using a combination of a high-contrast CytoViva imaging system and a particle image velocimetry camera, which can capture images at speeds greater than 800 frames/s. Using this system, we discovered that, during rapid swimming of Giardia trophozoites, undulations of the caudal region contributed to forward propulsion combined with the beating of the flagella pairs. It was also discovered, in contrast to previous studies with 10 times slower image sampling technique, that the anterior and posterolateral flagella beat with a clearly defined power stroke and not symmetrical undulations. During the transition from free swimming to attachment, trophozoites modified their swimming behavior from a rapid rotating motion to a more stable planar swimming. While using this planar swimming motion, the trophozoites used the flagella for propulsion and directional control. In addition to examination of the posterolateral and anterior flagella, a model to describe the motion of the ventral flagella was derived, indicating that the ventral flagella beat in an expanding sine wave. In addition, the structure of the ventrocaudal groove creates boundary conditions that determine the form of beating of the ventral flagella. The results from this study indicate that Giardia is able to simultaneously generate both ciliary beating and typical eukaryotic flagellar beating using different pairs of flagella.