96-7 Monday, Jan. 6 15:00 - 15:15 Gait Rhythmogenesis and Spatiotemporal Ordering in Self-propelling Unicellular Microorganisms WAN, KY; University of Exeter, UK email@example.com http://www.micromotility.com
Interlimb coordination is a highly dynamic phenomenon which enabled the first vertebrates to negotiate terrestrial habitats during the evolutionary transition from sea to land. Surprisingly, attainment of complex limb coordination is by no means exclusive to organisms that possess a nervous system. Instead, single-celled microeukaryotes, which may be mere microns in size, can also enact complex movement gaits for swimming using multiple, fast-moving locomotor appendages called cilia and flagella. These appendages are structurally and functionally similar to epithelial cilia, which in mammalian systems are responsible for directional flow generation and transport. Here, I demonstrate novel features of spatiotemporal flagellar coordination in unicellular algae. I show that the algal flagellar apparatus - comprising basal bodies and interflagellar fibres - actively couples groups of flagella to achieve dynamic locomotor patterning. Resolving gait dynamics at the single-flagellum level in both free-swimming and micropipette-fixed individuals, I will demonstrate spontaneous transitions in behaviour including gait-intermittency, reversible rhythmogenesis, and gait-mechanosensitivity. In particular, during forward propulsion quadriflagellate algae can actuate four flagella to assume trotting or gallop gaits, but oscillations can be activated/inactivated selectively in subsets of the flagella. These findings suggest that a network of intracellularly-coupled algal flagella can function as a central pattern generator, which allows for distinguishable control and ordering of individual oscillators in the network and thus complex symmetry-breaking dynamics. Such symmetry-breaking processes provide a means for cell reorientation (such as towards light for photosynthesis) and responsive navigation in complex environments.