1. 1.

    Skeletal, muscular and neural organization of the two distal joints (J2 and J3) of the antenna of the rock lobster Palinurus vulgaris has been described.

  2. 2.

    Motor innervation (nine motoneurones) of the two distal joints of the antenna has been determined by anatomical and physiological methods. Extensor and flexor muscles of J2 and J3 are each innervated by one specific excitatory tonic motoneurone. One excitatory phasic motoneurone is common to both the J2 and J3 extensor muscles, another to the J2 and J3 flexor muscles. The J3 extensor muscle also receives a specific phasic motoneurone. An accessory extensor muscle which spans J2 and J3 is innervated by one excitatory motoneurone. A common inhibitory motoneurone innervates the two flexor and the two extensor muscles of J2 and J3.

  3. 3.

    Movements of J2 and J3 are sensed by a proprioceptor (chordotonal organ). Reflex patterns involving this proprioceptor have been extensively studied. Sinusoidal extension-flexion movements imposed on the J3 joint induced intra-segmental reflexes (on the J3 muscle innervations) and inter-segmental reflexes (on the J2 muscle innervations) which exclusively involved the tonic excitatory motoneurones and the common inhibitory motoneurone.

  4. 4.

    Resistance reflexes (activation of the muscle stretched by the imposed movements) occurred whatever the excitability level of the animal and involved both flexor and extensor motoneurones. The motoneurones spiked at a higher frequency when the velocity of the imposed movement was increased. The common inhibitor motoneurone was activated during extension movements.

  5. 5.

    In preparations which became ‘more excitable’, assistance reflexes could be induced by joint stimulations which formerly induced resistance reflexes. Sometimes assistance reflexes could be induced by increasing the velocity of the movements imposed on J3. Assistance reflexes mainly involved extensor motoneurones.

  6. 6.

    The role of the tonic, phasic and inhibitory innervations and the functional significance of resistance and assistance reflexes are discussed in relation to the behavioural role of the rock lobster antenna.

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