Machemer-Röhnisch S, Bräucker R, Machemer H (1998): Graviresponses of gliding and swimming Loxodes striatus using step transition to weightlessness

ABSTRACT. 
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 (µg) during free fall in a 500-m drop shaft.  Cellular locomotion inside a vertical experimental chamber was recorded preceding transition to µg, and during 10 s 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 concentration near 40% air saturation, gliders showed a positive gravitaxis, and this was even more pronounced in swimmers. In µg gravitaxis of gliders relaxed within 5 s, whereas gravitaxis relaxation of swimmers was not completed even after 10 s.  Analysis of the locomotion rates during the g-step transition revealed the sedimentation rates of gliders (14 µm/s) and swimmers (45 µm/s).  The gravikinesis of gliders fully cancelled the sedimentation effects during upward and downward locomotion tending to maintain cells at a given level. The gravikinesis of swimming cells augmented the speed of the majority of cells during gravitaxis.