Intelligent motility control of biological swimmers

Many biological microswimmers, including sperm and motile green alga, navigate in noisy environments. For successful navigation, these swimmers integrate their active motion and sensory perception in tight feedback loops, relying on only minimal computational resources. We first discuss a geometric sampling strategy along helical paths that allows sperm cells from marine invertebrates to find the egg, even when the read-out of chemical orientation signals is extremely noisy. Swimming along curved paths allows these cells to actively probe their environment in a stereotypic manner, thereby structuring the type of sensory information the cells will perceive.

As a second example of intelligent motility control, we will present a purely mechanical feedback mechanism that allows a breast-swimmer-alga to coordinate its two flagellar swimming arms. Physical interaction with the surrounding fluid is essential to ensure a synchronized swimming gait. The robustness of these biological control mechanisms is reviewed in the presence of active fluctuations and extrinsic noise, which can be significant at the scale of cells.