Meeting Abstract

17.2  Saturday, Jan. 4 10:45  Effect of gravidity on jump performance and muscle physiology in the American locust KIRKTON, S. D.*; CARROLL, J. P.; Union College; Union College kirktons@union.edu

Trade-offs exist between different physiological characteristics. In terrestrial animals, the trade-off between gravidity (or load) on striding locomotion has been well documented. However, the effect of load on jumping performance is relatively unknown. In lizards, an increased load equal to 30% of body mass produced shorter and less frequent jumps. However in Schistocerca americana grasshoppers, 20% heavier gravid females have a similar jump performance as non-gravid females. We tested the hypothesis that grasshoppers vary their jumping muscle contraction duration to increase force produced when gravid (or loaded). We examined the effect of added mass on jump performance by attaching weights (20% or 40% of body mass) to gravid females, non-gravid females, and males. We used high speed video analysis to compare jump performance and electromyography to measure jumping muscle contraction times. Controls indicated that a 30 minute rest after electrode implantation was sufficient for the grasshoppers to regain their jumping ability. Results indicate that muscle contraction duration increases with increased weight. Thus, gravid (loaded) and non-gravid grasshoppers are equally capable of escaping predation. Unlike lizards, grasshoppers may show no effect of loading on jump performance because they use a catapult mechanism to store energy prior to jumping. Support was provided by Union College Student Research Grants.