Neurophysiology of a statocyst equilibrium reflex in the crab Carcinus maenas (L.)
The statocyst of Carcinus consists of two semicircular canals at right angles to each other. The canal system is open. Within the statocyst four hair types are identified and described, thread hairs, free hook hairs, statocyst hairs and group hairs. The response of the thread hair and free hook hair nerve to oscillation about the horizontal and vertical axis was examined for they are known to provide an input to fibre 5, the command fibre involved in the righting reflex and tilt evoked reflexes. The thread hair and free hook hair have responded to oscillation: about both, the horizontal and vertical axis at frequencies up to 100Hz. The response of the thread hair was dependent on the position of the statocyst in the gravitational, field whereas that of the free hook hairs was independent. The anatomy of fibre 5 and the central projections of the motorneurones supplying the basal leg muscles was studied in the thoracic ganglionic mass as a preliminary to examination of possible neural connections by intracellular recording.