Meeting Abstract
Earthworms locomote in confined spaces and underground via retrograde peristaltic gaits where a transient substrate anchor is formed by the contraction of longitudinal muscles. Here, via laboratory studies of the earthworm Lumbricus terrestris, we reveal how the locomotion ability of the worms is enhanced via lateral bending and buckling of body segments. Depending on absence or presence of contact between the animal’s body and environment, worms control the shape of their slender-flexible bodies (usually bending tip or tail) to generate thrust and maneuver in three dimensions. To study the benefits of this behavior, we allowed the earthworms (L = 26.95 ± 6.18 cm and m = 7.49 ± 2.04 g, n = 10) to crawl in a large acrylic tube (d = 1.0 cm, l = 1 m, d > worm diameter) while varying the tube angle from 0 to 90°. We calculated the average body length per gait cycle (BL/cyc) over several cycles. At a 0° incline, the worms had the largest (0.201 ± 0.075) BL/cyc and mostly moved by peristaltic gait. The worms had the lowest (0.076 ± 0.016) BL/cyc at a 90° incline but could still climb without significant slipping. At higher degree angles, such as 75 and 90°, the body bending was more prevalent than at lower angles, providing extra anchoring points for the forward locomotion and reducing the occurrences of slipping. Our results reveal that adequate control of body shape can help limbless terrestrial animal locomote in diverse environments. Moreover, this movement strategy has aided design of the control system of a soft earthworm-inspired robot.
