Graviperception and Graviresponses of Paramecium

The behavioral responses of a swimming sensory cell (Paramecium) were investigated under the conditions of a real (TEXUS 27, 28) and simulated weightlessness (fast-rotating clinostat). After onset of 0 g, gravitactic orientation persisted for about half a minute before random swimming was achieved. Lack of phobicresponses and straight-on swimming paths exclude depolarisation of the cell's membrane to an amount of action potential. Increased swimming velocity under 0 g might be induced by a hyperpolarisation of the membrane and/or an increase of cAMP