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PATTERNS OF LOCOMOTION ACTIVITY DURING HYPER-GRAVITY IN LARVAL DROSOPHILA MELANOGASTER.  M.J. Potthoff and J.N. Thompson, Jr.  Dept. of Zoology, Univ. of Oklahoma, Norman.  

   Adult Drosophila are highly mobile and can detect and respond to changes in gravity.  Since larvae are slower and more limited in movement, it might be expected that their gravitational responses would be slight.  In contrast, we hypothesize that hypergravity can be a stress that will impede their mobility significantly.  A 22"-diameter centrifuge was constructed with a metal armature attached to a bearing assembly.  A pulley system was used to reduce the rate of revolution.  The drive wheel was attached to the power source, a variable-speed drill regulated by a rheostat.  RPM was quantified with a photocontact tachometer, and a gravitational force of 4 g could be maintained for extended periods.  Larval D. melanogaster were placed in a plastic arena where their behavior could be observed and videotaped using a miniature high resolution videocamera (ALM-2453 2.4 GHz Wireless Miniature Camera, 10ґ mag.).  Larval locomotion rate was measured by digitizing the larval position coordinates continuously during experimental periods of 70 minutes each (10 min taped acclimation;   30 min at 4 g;  30 min at 1 g).  Locomotion rate declined during exposure to 4 g (units of linear movement at 4 g: 1000.66 ± 884.47 s.d.; control: 1490.51 ± 1212.87;  t₁₅₀ = 2.68, P < 0.01), but began to return to normal when larvae returned to 1 g (for those that showed movement, 0-10 min post treatment = 938.29 ± 914.07; 20-30 post treatment = 1457 ± 1192.00;  t₆₆ = 2.03, P < 0.05).  Larvae were frequently observed to exhibit an enhanced escape-like behavior (positive geotaxis) during and after exposure to hypergravity.   Locomotion is reduced under hypergravity, but larvae are still able to move effectively and feed.  Treatment at 4 g is stressful enough to stimulate escape reactions, and we predict that increased hypergravity and exposure time will make these even stronger. 

(Supported by NASA: NAG2-1427; and UROP Undergraduate Research Grant).