[Changes in the otolithic apparatus of rats and fish after long-term rotation with increased acceleration]

Otolith membranes of the utriculus and sacculus of rats exposed to 2 g during a month showed a typical size-related distribution of otoconia, which had optic activity. The length (L) and diameter (D) of utricular otoconia were linearly correlated as follows: D = 0.4 + + 0.4 L (microns). During chronic acceleration the mean size of utricular otoconia tended to diminish. Guppy fish were rotated at 1.8-2.2 g for 4 months and showed an absolute and a relative increase of the saccular mass when compared to the mass of the utricular or lagenar otolith. During chronic centrifugation the microrelief of the auditory sulcus of the saccular otolith changed. It can be concluded that prolonged centrifugation causes structural changes in the otolith apparatus of terrestrial and water animals which are probably of adaptive character.