TRIBLEHORN, J.D.*; YAGER, D.D.; Univ. of Maryland, College Park; Univ. of Maryland, College Park: Mantis auditory interneuron 501-T3 responses and the triggering of the evasive response during bat attack sequences.

Bat vocalization parameters (such as pulse repetition rate-PRR and pulse duration-PD) change predictably as they approach and capture prey. A flying mantis could use these changes to assess the level of danger posed by an attacking bat to initiate an evasive maneuver. To determine how well the mantis ultrasound-sensitive interneuron 501-T3 encodes vocalizations during a bat attack, we implanted an electrode to extracellularly record the 501-T3 responses to flying bat attacks in a large flight room. In the flight room, the bat attack sequence has three phases: approach (low PRR, >3ms PD), buzz I (increasing PRR, decreasing PD), and buzz II (very high PRR, <1.5 ms PD). 501-T3 responds to each vocalization emitted during the approach phase with multi-spike bursts containing 3-5 action potentials. 501-T3 can follow at PRRs up to 55 pulses/s. As PRR increases and PDs fall below 3 ms during buzz I, 501-T3 ceases burst responses. On average, spike bursts ceased 255.94 + 58.47 ms (72.0 + 15.14 cm away from the prep) before contact. To determine when the mantis evasive response occurs during an attack, we simulated the PRRs and PDs of several flying bat attack sequences and presented them to tethered flying mantids. For sequences with a rapid transition from the approach phase to the buzz II phase, the evasive response occurs close to the �contact� time of the simulated train. However, the evasive response occurs earlier if the transition is gradual. These results suggest that a bat could possibly circumvent the mantid�s auditory defense by increasing its PRR close to the point of capture or �tip off� the mantis by increasing its PRR too early. [Supported by: NSF IBN-9808859 (DDY) and NRSA F31MH12025 (JDT)]