Joint Receptors in the Antennule of Panulirus Argus Latreille

1. A single elastic strand organ, presumably a chordotonal proprioceptor, occurs at each of the three distal joints of the antennule in Panulirus argus. These organs are essentially identical with those described at the joints of the pareiopods. 2. Movement at the second and third joints is along one dorso-ventral axis. Unidirectional movement and position receptors responding to flexion and extension occur at both joints. 3. Movement at the first joint is biaxial, either dorso-ventral or medio-lateral. Many unidirectional movement and position receptors are non-specific to axis, and respond to flexion along both axes or to extension along both axes. In addition, some completely specific position and movement receptors occur that respond to extension or to flexion only along one axis. No bi-directional axis-specific receptors were found. 4. Accessory strands act in conjunction with the main elastic strand during joint movement to produce differential stretch according to direction or axis of movement. It is suggested that such differential mechanical distortion is responsible for the part receptor specificity observed.