期刊
JOURNAL OF EXPERIMENTAL BIOLOGY
卷 213, 期 1, 页码 161-171出版社
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jeb.030940
关键词
Stylonychia mytilus; ciliate; behaviour; electrophysiology; mechanosensitivity; gravikinesis; gravitaxis; gravireceptor potential
类别
资金
- Deutsches Zentrum fur Luft- und Raumfahrt [50WB9923]
- Minister fur Bildung und Forschung of the Federal Republic of Germany
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.
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