An Approach to Observing and Quantifying Real-Time Mandibular Muscle Topology in the Trap-Jaw Ant Odontomachus monticola by Synchrotron Imaging

The antOdontomachus monticolahas a pair of elongated mandibles that can manipulate a variety of objects including food, brood and nestmates. Anatomical and theoretical studies indicate that different tasks may require modification of mandible speed and force which is achieved by modulating the respective activity of three sets of muscles. Despite the advanced investigations on how muscles separately control the mandible movements in trap-jaw ants, real-time visualization of the muscle activity has remained elusive. In this investigation, we developed an approach based on the synchrotron imaging technique to elucidate the real-time topology of the muscles in the head of the ant. Using synchrotron imaging, we described the topology of the living ant's mandible muscles and calculated area changes in the intracranial muscles, which reflected the respective muscle's activities in the strike of mandibles. This study provides the first visualization evidence which validates that the mandible strike is facilitated by the contraction of adductor muscles, without the activation of abductor muscles.