A gravity-induced regulation of swimming speed in Euglena gracilis

We investigated the autotrophic flagellate Euglena gracilis for gravity-induced modulation of the speed of swimming as previously documented for larger protozoan cells. Methods of video-tracking of swimming and sedimenting cells under 1 g and hypergravity up to 2 g, and computer-assisted data proces...

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Bibliographic Details
Published in:Journal of Comparative Physiology 1999-12, Vol.185 (6), p.517-527
Main Authors: Machemer-Röhnisch, S., Nagel, U., Machemer, H.
Format: Article
Language:English
Subjects:
Acceleration
Augmentation
Chain dynamics
Data processing
Euglena
Euglena gracilis
Gravitation
Hypergravity
Immobilized cells
Linear functions
Molecular motion
Protozoa
Sedimentation
Swimming
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Summary:We investigated the autotrophic flagellate Euglena gracilis for gravity-induced modulation of the speed of swimming as previously documented for larger protozoan cells. Methods of video-tracking of swimming and sedimenting cells under 1 g and hypergravity up to 2 g, and computer-assisted data processing were applied. The vertical and horizontal swimming speed, and sedimentation rates of immobilized cells, were found to be linear functions of acceleration. Accounting for sedimentation in the observed upward and downward movements of Euglena, the active component of speed (propulsion) rose in proportion to acceleration. No saturation of gravikinesis was seen within the g-range tested. Gravity-dependent augmentation of speed was maximal in upward swimmers and decreased continuously over horizontal to downward swimmers. Linear extrapolations of the data to zero-g conditions suggest the absence of a threshold of gravikinesis in Euglena. Energetic considerations indicate a high sensitivity of gravitransduction near the level of Brownian molecular motion.
ISSN:0340-7594
1432-1351
DOI:10.1007/s003590050412