Behaviour 2019
Leg loss decreases endurance and increases oxygen consumption during locomotion in harvestmen
Ignacio Escalante1, 2, Veronica Ellis2, Damian Elias2. 1University of Wisconsin, Milwaukee, Wisconsin, United States; 2University of California, Berkeley, California, United States

Animal movements are highly constrained by morphology and energetics. In addition, predictable bodily damage can constrain locomotion. We tested if losing legs affects the distance travelled over time and the metabolic costs of locomotion in Nelima paessleri harvestmen. These arachnids voluntary releases legs in response to predation attempts. We used flow-through respirometry as animals moved on a treadmill inside a sealed chamber. We found that endurance decreased gradually with an increasing number of legs lost. Interestingly, oxygen consumption increased only for harvestmen that lost three legs, but not for individuals that lost only a single leg. These results have different ecological and evolutionary implications. Reduced endurance may impair an animal's ability to continue moving away from potential predators, while increased oxygen consumption makes movement costlier. Our findings suggest that individuals have a threshold number of legs that can be lost before experiencing measurable energetic consequences. Our findings illustrate how animals respond to morphological modifications that affect the physiology of locomotion.