Meeting Abstract
Cockroaches show remarkable robustness to leg loss, but locomotion is more energetically costly. Previously, we discovered that the loss of one and both middle legs increased the cost of locomotion for cockroaches, Blaberus discoidalis. Here, we test the hypothesis that the increased cost relates to a decrease in endurance. We ran cockroaches on a treadmill until they could no longer match the set speed (30-220 m/s) and used the time to exhaustion as a measure of endurance. Simultaneously, we measured steady-state oxygen consumption, stride frequency, and ground contact time. We compared endurance for individuals missing one and two middle legs to intact controls. For all conditions, oxygen consumption increased with speed from 30 to 170 mm/s, but ceased to increase above 170 mm/s, the maximum aerobic speed. There was not a significant change in endurance associated with the loss of one leg. After the loss of two legs, endurance decreased across the range of speeds. At the maximum aerobic speed, endurance decreased by 34% to 10.6 min. Endurance correlated more strongly with stride frequency and ground contact time than with the rate of oxygen consumption. After losing two middle legs, cockroaches took shorter, faster steps to maintain the same speed and fatigued more quickly. Although leg loss altered the relationship between speed and stride frequency and between speed and ground contact time, differences in leg number did not affect the relationship between endurance and these two metrics. The decline in endurance appears to depend on the increased rate of force production.
