Rotation speed of labyrinthectomized fish during short-duration weightlessness

This study used blind unilaterally labyrinthectomized goldfish of 5 to 15 cm body length. These goldfish were flown in parabolic flights to temporarily effect the loss of the second vestibular apparatus. Flights took place between 1 and 72 h after the operation. Attitude in 3 axes was recorded on video and analyzed from single-frame pictures for speed and direction of rotation about the roll (fish's body longitudinal) axis. Labyrinthectomy resulted in a rotation pattern consistent with literature under normal Earth-G conditions. Under diminished G-influence, the rotations, contrary to our expectation, did not stop, but, rather, increased in speed by a factor of 2 to 4. The direction of rotation did not change. The fish readapted to the low-G environment rapidly and returned to the rotation speeds observed before entry into the parabolas during the 5 to 7 s of parabola duration. Current theories for the generation of adaptation are discussed and their merits in explaining the experimental data are compared.