  Living creatures exhibit a remarkable diversity of locomotion mechanisms,
evolving structures specialised for interacting with their environment. In the
vast majority of cases, locomotor behaviours such as flying, crawling, and
running, are orchestrated by nervous systems. Surprisingly, microorganisms can
enact analogous movement gaits for swimming using multiple, fast-moving
cellular protrusions called cilia and flagella. Here, I demonstrate
intermittency, reversible rhythmogenesis, and gait mechanosensitivity in algal
flagella, to reveal the active nature of locomotor patterning. In addition to
maintaining free-swimming gaits, I show that the algal flagellar apparatus
functions as a central pattern generator which encodes the beating of each
flagellum in a network in a distinguishable manner. The latter provides a novel
symmetry-breaking mechanism for cell reorientation. These findings imply that
the capacity to generate and coordinate complex locomotor patterns does not
require neural circuitry but rather the minimal ingredients are present in
simple unicellular organisms.
