Is gravikinesis in Paramecium affected by swimming velocity?

Negative gravikinesis is an acceleration-activated modulation of vertical swimming velocity which can neutralize the passive sedimentation of ciliates. This paper investigates effects of swimming velocity levels on gravikinesis. Evaluation of a large number of data of free swimming cells with veloci...

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Bibliographic Details
Published in:European journal of protistology 1996-10, Vol.32, p.90-93
Main Authors: Machemer, Hans, Machemer-Röhnisch, Sigrun
Format: Article
Language:English
Subjects:
Gravikinesis
Mechanosensory transduction
Paramecium
Rheokinesis
Swimming velocity
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Summary:Negative gravikinesis is an acceleration-activated modulation of vertical swimming velocity which can neutralize the passive sedimentation of ciliates. This paper investigates effects of swimming velocity levels on gravikinesis. Evaluation of a large number of data of free swimming cells with velocities ranging from 500 to 2000 μm/s show that the ratio of vertically upward (and downward) swimming cells over horizontally swimming cells is represented by linear functions with slopes of 1. This is equivalent to a constant value of gravikinesis ( Δ) in upward swimming cells ( Δ U) and downward swimming cells ( Δ D) irrespective of the swimming rate. Mechanoresponses due to velocity-dependent membrane deformations (rheokinesis) do not affect determinations of gravikinesis and may not exist at all. DC-field stimulation interferes with the slopes of swimming rates depressing vertical velocities as referred to horizontal velocity. The reduction of slopes (< 1) in the presence of an external voltage gradient implies a feedback of voltage-dependent activation of gravireceptor channels on the electric motor control of the cilia.
ISSN:0932-4739
1618-0429
DOI:10.1016/S0932-4739(96)80083-6