Department of General Zoology and Neurobiology, Ruhr-University Bochum, D-44780 Bochum, Germany.
J Exp Biol. 2010 Jan 1;213(1):161-71. doi: 10.1242/jeb.030940.
The graviperception of the hypotrichous ciliate Stylonychia mytilus was investigated using electrophysiological methods and behavioural analysis. It is shown that Stylonychia can sense gravity and thereby compensates sedimentation rate by a negative gravikinesis. The graviresponse consists of a velocity-regulating physiological component (negative gravikinesis) and an additional orientational component. The latter is largely based on a physical mechanism but might, in addition, be affected by the frequency of ciliary reversals, which is under physiological control. We show that the external stimulus of gravity is transformed to a physiological signal, activating mechanosensitive calcium and potassium channels. Earlier electrophysiological experiments revealed that these ion channels are distributed in the manner of two opposing gradients over the surface membrane. Here, we show, for the first time, records of gravireceptor potentials in Stylonychia that are presumably based on this two-gradient system of ion channels. The gravireceptor potentials had maximum amplitudes of approximately 4 mV and slow activation characteristics (0.03 mV s(-1)). The presumptive number of involved graviperceptive ion channels was calculated and correlates with the analysis of the locomotive behaviour.
使用电生理学方法和行为分析研究了旋口虫（Stylonychia mytilus）的重觉感知。结果表明，旋口虫可以感知重力，并通过负向重趋性来补偿沉降速度。重响应由速度调节的生理成分（负向重趋性）和额外的定向成分组成。后者主要基于物理机制，但也可能受到纤毛反转频率的影响，纤毛反转频率受生理控制。我们表明，重力的外部刺激被转化为生理信号，激活机械敏感的钙和钾通道。早期的电生理学实验表明，这些离子通道在表面膜上以两种相反的梯度分布。在这里，我们首次展示了旋口虫重感受器电位的记录，这些记录可能基于这种双梯度离子通道系统。重感受器电位的最大幅度约为 4 mV，激活特性缓慢（0.03 mV s(-1)）。计算了参与重觉感知的离子通道的假定数量，并与运动行为的分析相关联。
