Statocyst-Induced Eye Movements in the CrabScylla Serrata

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Abstract
1. Irrigation of the statocysts of the crab Scylla serrata will activate the oculomotor neurones associated with eye movements. 2. An investigation of the central mechanism of statocyst-induced nystagmus has been started with the description of the statocyst canals and a characterization of the sensory input from the hair receptors in the canals. 3. The canals are shaped like two toroids joined at approximately right angles to one another. Direct observation of isolated statoliths and glass models of them shows that when they are rotated, fluid moves around the circumference of the statocyst canals and displaces the hair receptors protruding into them. The direction of displacement of the different groups of receptors in both statocysts is related to the axes of rotation and provides a unique output for rotation about each axis. 4. Electrical recordings from the three types of receptor hairs show that the thread hairs are most probably the receptors responsible for detection of rotation about the vertical axis. The free hook hairs are sensitive enough to detect rotation about the horizontal axes. The statolith hairs are sensitive to maintained changes of position.