Antennal pointing responses to physical looming in tethered and untethered crickets
The escape response is an adaptive behavioral mechanism for escape from a predator. Crickets escape with actions such as turning, running, and jumping. In addition to escape behaviors, crickets have been observed to rotate their antennae toward a looming stimulus, known as pointing. Pointing may facilitate escape through antennal contact with a predator. Due to the likely role of pointing in escape, experimental tethering, which prevents escape, may affect the pointing response in crickets. However, there has been no research directly comparing pointing in tethered and untethered crickets. The present study compared the pointing responses in tethered and untethered crickets to determine the effect of tethering on pointing. A looming stimulus, represented by a ball propelled at 45o at tethered and untethered crickets, was applied from different directions. Antennae movements were recorded with a high-speed video camera and antennae angles was calculated throughout the response. In tethered crickets, the antenna closest to the looming ball executed a pointing response toward the ball; the contralateral antenna did not. Angular change of the pointing antenna was dependent on stimulus direction. Untethered crickets pointed toward the ball, but the angular change did not depend on the stimulus direction. Therefore, tethering reveals a dependence of pointing on stimulus direction.