Limb loss and specialized leg dynamics in tiny water-walking insects

Abstract

AbstractThe air-water of the planet’s water bodies, such as ponds, lakes and streams, presents an uncertain ecological niche with predatory threats from above and below. AsMicroveliamove across the water surface in small ponds, they face potential injury from attacks by birds, fish, and underwater invertebrates. Thus, our study investigates the effects of losing individual or pairs of tarsi on theMicrovelia’sability to walk on water. Removal of both hind tarsi causesMicrovelia spp. to rock their bodies (yaw) while running across the water surface at ±19°, compared to ±7° in non-ablated specimens. This increase in yaw, resulting from the removal of hind tarsi, indicates thatMicroveliause their hind legs as ‘rudders’ to regulate yaw, originating from the contralateral middle legs’ strokes on the water’s surface through an alternating tripod gait. Ablation of the ipsilateral middle and hind tarsi disrupts directionality, makingMicroveliaturn in the direction of their intact limbs. This loss of directionality does not occur with the removal of contralateral middle and hind tarsi. However,Microvelialose their ability to use the alternating tripod gait to walk for water walking on the day of contralateral ablation. Remarkably, by the next dayMicroveliaadapt and regain the ability to walk on water using the alternating tripod gait. Our findings elucidate the specialized leg dynamics within the alternating tripod gait ofMicrovelia spp., and their adaptability to tarsal loss. This research could guide the development and design strategies of small, adaptive, and resilient micro-robots that can adapt to controller malfunction or actuator damage for walking on water and terrestrial surfaces.