New theory sheds light on how soft bodies move

New theory sheds light on how soft bodies moveCreeping along slowly, star fish are propelled by hundreds of tube feet, but these are no ordinary limbs.The feet have more in common with your tongue or an elephant's trunk.Without bones for support, these so-called hydrostatic structures depend on internal fluid pressure to deform and move, 'like pressing on a water balloon', says Matt McHenry from University of California (UC), Irvine, USA, explaining that by squeezing a hydrostatic structure with muscles, it can expand in other directions, like sticking out your tongue.However, as McHenry and his colleagues Olaf Ellers and Amy Johnson (Bowdoin College, USA) looked closer into how star fish tube feet work, they began to realise that no one really understood how these fleshy structures exert forces.McHenry recalls, 'Amy and Olaf were supposed to be in my lab on sabbatical', but COVID19 put paid to that, so the team got their heads together over Zoom instead to create a theory for how hydrostatic skeletons exert forces and how those forces change as hydrostatic limbs extend.