Date of Award
Locust, latch mediated spring actuated, locust jump, movement control, jumping insects.
During the adult reproductive stage, female locusts (Schistocerca americana) experience multiple ovigerous cycles during which they undergo significant weight gain. The magnitude of their weight change is thought to negatively impact the kinematics of the locust jump during the gravid phase. We hypothesized that this decrease in performance would result in an evolutionary pressure for female locusts to develop an intrinsic means to detect increases in body mass and respond with a modulation in their movement. Based on this hypothesis, we predicted that the female locusts would display a consistent jump performance in response to weight change, facilitated by a change in the contraction time of their extensor tibiae muscles. Conversely, this type of control is not expected in male locusts since they do not experience the same cycles of weight. These predictions were tested using an artificial weight gain system to induce weight gains similar to natural changes. Simultaneous high-speed video capture (1500 frames per second) and bilateral electromyogram (EMG) recordings were obtained from nine female and five male locusts during evoked escape jumps. Multiple jumps were recorded for each individual, corresponding to different artificial weight gain conditions. The peak angular velocity of the jumping legs was calculated using position tracking software (DeepLabCut) and subsequent kinematic analysis of the leg rotation using custom scripts in R. Contraction time was calculated from the extensor tibiae muscle EMG recordings. Female and male locusts maintained consistent peak angular velocity during extensions of their jumping legs in response to weight gain, indicating that both sexes modulate jump performance for different body masses. Furthermore, both sexes displayed increased contraction times for small weight increases, but contraction times for large weight increases were comparable to those of their natural body mass.
Ringer, Christopher, "The effect of weight gain on the neuromechanics of locust jumps (Schistocerca americana)" (2023). Honors Theses. 2736.