The cooperative organization of dynamic biological processes often requires coordination via chemical signaling. Riedel et al. found that, when attached to a surface, a critical number of sperm cells self-organized into a hexagonally packed array of rotating vortices where each vortex consisted of about 10 hydrodynamically synchronized cells forming a quantized rotating wave. This spatial-temporal pattern of entrained sperm cells formed in the absence of chemical cell-cell signaling, leading to a new coordination concept of cooperative cilia and flagella. Thus, single cells and microorganisms can be hydrodynamically coordinated without the need for chemical signaling.
I. H. Riedel, K. Kruse, J. Howard, A self-organized vortex array of hydrodynamically entrained sperm cells. Science 309, 300-303 (2005). [Abstract] [Full Text]
