GRAVIRESPONSES OF GLIDING AND SWIMMING LOXODES USING STEP TRANSITION TO WEIGHTLESSNESS

Cells of Loxodes striatus were adjusted to defined culturing, experime ntal solution, O-2-supply, temperature, and state of equilibration to be subjected to step-type transition of acceleration from normal gravi ty (1 g) to the weightless condition (mu g) during free fall in a 500- m drop shaft. Cellular locomotion inside a vertical experimental chamb er was recorded preceding transition and during 10 s of mu g. Cell tra cks from video records were used to separate cells gliding along a sol id surface from free swimmers, and to determine gravitaxis and graviki nesis of gliding and swimming cells. With O-2 concentrations greater t han or equal to 40% air saturation, gliders and swimmers showed a posi tive gravitaxis. In mu g gravitaxis of gliders relaxed within 5 s, whe reas gravitaxis relaxation of swimmers was not completed even after 10 s. Rates of horizontal gliders (319 mu m/s) exceeded those of horizon tal swimmers (275 mu m/s). Relaxation of gravikinesis was incomplete a fter 10 s of IJ-S Analysis of the locomotion rates during the g-step t ransition revealed that gliders sediment more slowly than swimmers (14 versus 45 mu m/s). The gravikinesis of gliders cancelled sedimentatio n effects during upward and downward locomotion tending to maintain ce lls at a predetermined level inside sediments of a freshwater habitat. At greater than or equal to 40% air saturation, gravikinesis of swimm ers augmented the speed of the majority of cells during gravitaxis, wh ich favours fast vertical migrations of Loxodes.