Learning from the Hawaiian bobtail squid: How cilia pump, filter, and mix fluid on a microscale

Cilia are microscopic, hair-like structures on the cell surface that can propel the extracellular fluid environment. I am interested in understanding how cilia populations coordinate their beat pattern and how this collective activity generates particular flow patterns and transport functions. Here, I present a case study in the Hawaiian bobtail squid that investigates the relationship between collective ciliary activity and resulting fluid flow, leading, in this case, to the recruitment of symbiont bacteria. In particular, I will present experimental and computational data demonstrating how the squid's internal cilia act like a microfluidic device that actively filters the water for potential bacterial candidates and also provides a sheltered zone, allowing for accumulation of mucus and bacteria into a biofilm. Moreover, in this sheltered zone, cilia-driven flows enhance the spread of biochemical signals that could facilitate specific bacteria host recognition. These results suggest that studying cilia activity on the population level might reveal a diverse range of microfluidic transport and sensing functions. Studying cilia as functional building blocks could ultimately inspire the design of ciliated robots and devices.