Graviresponses of gliding and swimming Loxodes using step transition to weightlessness.
Cells of Loxodes striatus were adjusted to defined culturing, experimental solution O2-supply, temperature, and state of equilibration to be subjected to step type transition of acceleration from normal gravity, (1 g) to the weightless condition (microgravity) during free fall in a 500 m drop shaft. Cellular locomotion inside a vertical experimental chamber was recorded preceding transition and during 10 s of microgravity. Cell tracks from video records were used to separate cells gliding along a solid surface from free swimmers, and to determine gravitaxis and gravikenesis of gliding and swimming cells. With O2 concentrations > or = 40% air saturation gliders and swimmers showed a positive gravitaxis. In microgravity gravitaxis of gliders relaxed within 5 s whereas gravitaxis relaxation of swimmers was not completed even after 10 s. Rates of horizontal gliders (319 micrometers/s) exceeded those, of horizontal swimmers (275 micrometers/s). Relaxation of gravikinesis was incomplete after 10 s of microgravity. Analysis of the locomotion rates during the g-step transition revealed that gliders sediment more slowly, than swimmers (14 versus 45 micrometers/s). The gravikinesis of gliders cancelled sedimentation effects during upward and downward locomotion tending to maintain cells at a predetermined level inside sediments of a freshwater habitat. At > or = 40% air saturation, gravikinesis of swimmers augmented the speed of the majority of cells during gravitaxis, which favours fast vertical migrations of Loxodes.
Machemer-Rohnisch
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S
Arbeitsgruppe Zellulare Erregungsphysiologie, Ruhr-Universitat, Bochum, Germany.
Braucker
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R
Machemer
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H
D000818:Animals; D016798:Ciliophora / Q000502:physiology*; D006112:Gravitation; D018466:Gravity Sensing / Q000502:physiology*; D008124:Locomotion; D009043:Motor Activity; D013550:Swimming; D013997:Time Factors; D014893:Weightlessness