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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7450

Sigrun Machemer-Rohnisch, Richard Braucker, and Hans Machemer; Graviresponses of Gliding and Swimming Loxodes Using Step Transition to Weightlessness. J.Eukaryot.Microbiol. 45(4):411-418, 1998

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Cells of Loxods 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 (µg) during free fall in a 500-ml drop shaft. Cellular locomotion inside a vertical experimental chamber was recorded preceding transition and during 10 sec of µg. Cell tracks from video records were used to separate cells gliding along a solid surface from free swimmers, and to determine gravitaxis and gravikinesis of gliding and swimming cells. With O2 concentrations >/_40% air saturation, gliders and swimmers showed a postivie gravitaxis. In ug gravitaxis of gliders relaxed within 5 sec, whereas gravitaxis relaxation of swimmers was not completed even after 10 sec. Rates of horizontal gliders (319 µm/sec) exceeded those of horizontal swimmers (275 µm/sec). Relaxation of gravikinesis was incomplete after 10 sec of µg. Analysis of the locomotion rates during the g-step transition revealed that gliders sediment more slowly than swimmers (14 versus 45 µm/sec). 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 >/_40% air saturation, gravikinesis of swimmers augmented the speed of the majority of cells during gravitaxis, which favours fast vertical migration of Loxodes.