Physical and physiological properties of the crayfish antennal flagellum.

(1) Mechanoreceptors in the crayfish antennae are divided into four functional categories: vibration (13%), bidirectional displacement (19%), unidirectional displacement (45%), and position (23%) receptors. The distribution of receptors along the length of the flagellum follows a logarithmic progression, decreasing from about 40% at the base to less than 5% at the tip. (2) Vibratory stimulation of the antennae was found to induce a traveling wave. Because of an impedance gradient along the length of the flagellum, the traveling wave moves most efficiently from base to tip. The wave was observed to travel at an average velocity of 6.0 m/sec. (3) Large deflections of the tip are not uniformly transferred to the base, but decrease logarithmically. This due to the existence of the impedance gradient. (4) Receptor output probability was found to be greatest when low frequency/high intensity stimulation was applied to the flagellar base. (5) Characteristics of large (2 cm) posterior-going deflections of the flagellar tip that are effective in producing response differences are displacement: (a) amplitude, (b) velocity, and (c) acceleration.