All animals possess a nervous system which controls their functions and behaviour. That is, all but a few! The tiny pancake-like marine animal Trichoplax is one of the very few exceptions to this rule, being able to perform complex functions and movements without neurons or muscle. 

Trichoplax crawls on substrates such as rocks and corals thanks to the beating of thousands of motile cilia present on its lower epithelium. To change the direction of its movements (for example in response to different attractive or repulsive cues) Trichoplax needs to change the orientation of its ciliary beating, but how exactly this occurs has been a mystery until recently. 

In a paper recently published in Current Biology, members of the ‘Evolution and morphogenesis of epithelia’ and ‘Physical approaches to cell dynamics and tissue morphogenesis’ teams showed that ciliary beating reorientation is due to the reorientation of the Basal Bodies, the structures that anchor each cilium within the cytoplasm of epithelial cells. Following mechanical stimulation, Trichoplax Basal Bodies are swiftly and co-ordinately reoriented throughout the lower epithelium, allowing the animal to modify the direction of its movements. Remarkably, this phenomenon is dependent on the influx of Ca2+ within the cells. 

These data show that a very simple cellular events can generate complex and sophisticated outputs at the whole organism scale.