The role of antennal hair plates in object-guided tactile orientation of the cockroach (Periplaneta americana)

The searching behavior of blinded cockroaches was examined under unrestrain ed conditions, in an arena, and on a treadmill. When cockroaches searching in 3 circular arena touched a stationary object (metal pole) with their ant ennae, they frequently approached the object more closely, and then climbed up it. Similar orientation behavior was observed in tethered animals in op en loop conditions, walking on a Styrofoam ball. In these restrained cockro aches, a single antenna sufficed to distinguish the angular positions of an object, in the horizontal plane (0 degrees, 45 degrees, and 90 degrees). A group of mechanosensitive hairs on the basal segment of the antenna (scapa l hair plate) appears to play a major role in antennal object detection in the horizontal plane, as gauged by shaving off these scapal hair plates. In unrestrained cockroaches, shaving the scapal hair plate increased the time needed to approach an object. Under tethered conditions, the ability to tu rn towards and to establish antennal contact with a test object was signifi cantly impaired.