title: Graviperception in the flagellate Euglena gracilis during a shuttle space flight.
abstract: During a recent space flight, gravitaxis of the unicellular photosynthetic flagellate, Euglena gracilis, was studied on board of the American shuttle Columbia.  Accelerations were varied between 0 and 1.5 x g using a slow rotating centrifuge microscope (NIZEMI).  The cells showed a sigmoidal response curve for the dependence of the precision of gravitaxis on acceleration which is indicative of the involvement of an active, physiological gravireceptor with a threshold at g-values < or = 0.16 x g and a saturation at g-values > or = 1 x g.  No adaptation to microgravity was found during the prolonged space mission.  After return the cells showed a normal gravitactic behavior at 1 x g.  Since the cells are heavier than water, their swimming velocity is affected by sedimentation.  The velocity distribution at different accelerations closely follows Stokes' law for sedimentation indicating that, in contrast to the ciliate Paramecium, E. gracilis, does not show any gravikinesis.
authors.affiliation: Institut für Botanik and Pharmazeutische Biologie der Friedrich-Alexander-Universität, Erlangen, Germany.
authors.forename: D P
authors.initials: DP
authors.lastname: Häder
authors.forename: A
authors.initials: A
authors.lastname: Rosum
authors.forename: J
authors.initials: J
authors.lastname: Schäfer
authors.forename: R
authors.initials: R
authors.lastname: Hemmersbach
mesh_terms: D000054:Acceleration; D000818:Animals; D002498:Centrifugation; D005056:Euglena gracilis / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D018471:Hypergravity; D007091:Image Processing, Computer-Assisted; D009068:Movement / Q000502:physiology; D013026:Space Flight; D013550:Swimming; D014893:Weightlessness