Antennal motor system of the cockroach, Periplaneta americana

Abstract

The organization of the antennal muscles, nerves, and motor neurons has been investigated in the cockroach, Periplaneta americana. Antennal movements have been observed by video analysis, muscle actions have been determined by dissection and direct mechanical testing, and the motor neurons innervating each muscle have been defined with a recently developed selective backfill method. A model of the antennomotor system of Periplaneta has thus been established and compared with that of crickets. Five muscles located within the head capsule insert on the most proximal antennal segment, the scape. By their action, they allow the scape to move in essentially any direction within the dorsoventral and anteroposterior planes. An additional pair of muscles, one dorsal and one ventral, are found within the scape. They insert on the pedicel and move the pedicel in the dorsal-ventral plane. These seven muscles are controlled by at least 17 motor neurons with somata located in the deutocerebrum. By their action, these motor neurons enable cockroaches to move the long flagellum of each antenna through a wide range of positions in the frontal space, medio-laterally, and also allow depression toward the substrate and elevation well above the level of the head. The antennal motor neurons have been classified into five morphological types based on soma and axon location. Each morphological type has been correlated with a particular pattern of muscle innervation and control. The neurites of all motor neurons are located along the medial aspect of the dorsal lobe of the deutocerebrum.