Meeting Abstract

16-7  Thursday, Jan. 5 11:30 - 11:45  Extreme asymmetry in the energy transfer rate of trap-jaw ant mandibles KUO, C-Y*; RUTA, A; THOMPSON, C; PATEK, SN; Duke University; Duke University; Charles E. Jordan High School; Duke University

Extremely high speeds and accelerations are achieved through power amplification: a class of mechanisms that reduce the duration over which work is performed. Animals contract slow, forceful muscles to store elastic potential energy in springs and then suddenly release potential energy through latch or catch mechanisms, which act as the critical barrier between the slow accumulation of potential energy and the rapid transduction to kinetic energy. Such asymmetry in energy flow and resultant power amplification is typically inferred, rather than measured, due to the challenges of measuring these movements at exceedingly short time scales. Therefore, a fundamental understanding of latching dynamics is still needed in order to fully incorporate the asymmetric energy flow of energy storage and release into the mechanisms of power amplification. We measured the timing of energy storage and latch release in the trap-jaw ant Odontomachus brunneus, which uses power-amplified mandible strikes for prey capture and escape jumps. Using high-speed videography (up to 300,000 frames/sec), we measured the duration of energy storage and captured the fleeting process of latch release in O. brunneus (energy storage: 8 ants; latch release: 11 ants; head length: 2.01-2.83 mm). Coupled with existing data on the duration of mandible strikes, we found that the temporal scales of the three stages spanned four orders of magnitude (energy storage: 10-1 s; latch release: 10-5 s; mandible strikes: 10-4 s). We also observed variation in the duration of energy storage and latch release both within and among individuals, although how this variation translates to variable kinematic output remains to be tested. These results highlight the extreme temporal asymmetries of energy flow and the critical role of latch release for fast, power-amplified movements.