期刊
EUROPEAN JOURNAL OF PROTISTOLOGY
卷 45, 期 2, 页码 98-111出版社
ELSEVIER GMBH
DOI: 10.1016/j.ejop.2008.09.001
关键词
Bursaria truncatella; Gravikinesis; Gravitaxis; Electrophysiology; Mechanosensitivity; Microgravity
类别
资金
- Deutsches Zentrum far Luft- und Raumfahrt (DLR) [50WB93193]
- Minister fur Wissenschaft und Forschung of the State of Nordrhein-Westfalen [A1-21600588]
Bursaria truncatella is a giant ciliate. Its volume of 3 x 10(7) mu m(3) and a sedimentation rate of 923 mu m s(-1) would induce the cell to rapidly sink to the bottom of a pond unless compensating mechanisms exist. The upward swimming behaviour of a cell population (negative gravitaxis) may be either a result of reorientations of the cells (graviorientation) and/or direction-dependent changes in propulsion rate (gravikinesis). The special statocyst hypothesis assumes a stimulation of mechanosensitive ion channels by forces of the cytoplasmic mass acting on the lower membrane. Here, we present basic electrophysiological data on B. truncatella. Investigation of the mechanosensitivity reveals a polar distribution of depolarising and hyperpolarising mechanosensitive channels at least on the dorsal membrane of the cell. Analysis of swimming behaviour demonstrates that Bursaria orients against the gravity vector (r(Oc) = 0.34) and performs a negative gravikinesis (-633 mu m s(-1)) compensating the sedimentation rate by 70%. Under hypergravity conditions gravitaxis in Bursaria is enhanced. Microgravity experiments indicate an incomplete relaxation of graviresponses during 4s of weightlessness. Experimental data are in accordance with the special statocyst hypothesis of graviperception, as was demonstrated in other ciliates. (C) 2008 Elsevier GmbH. All rights reserved.
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