Multiple beating cilia need some form of coupling to synchronise. In groups of cells, hydrodynamic coupling can be enough… but for single cells, it seems to be essential to have internal mechanical connections. In this case, does hydrodynamics play any role at all? In a new paper, just out in Physical Review Letters (Editors’ Suggestion!), we use a tip-less AFM cantilever (sub-micron thin!) to block hydrodynamic coupling between the two flagella of a single Chlamydomonas cell. The results highlight a striking difference between wild type, with its two different flagella, and the flagellar dominance mutant ptx1. This work was spearheaded by Luc Zorrilla (who’s just defended his thesis!), in collaboration with Antoine Allard (LOMA, U. Bordeaux) and Krish Desai (former MPhys student, Physics Department, U. Warwick).