Biology subjects

O'Neil, J. N.

Publications and source records attributed to O'Neil, J. N..

3 recordsLinked to original sources

bioRxiv2024

Epineuston vortex recapture enhances thrust in tiny water skaters

Vortex recapture underpins the exceptional mobility of natures finest fliers and swimmers. Utilized by agile fruit flies and efficient jellyfish, this phenomenon is well-documented in bulk fluids. Despite extensive studies on organismal locomotion at the waters surface, a vital fluidic interface where diverse life forms interact, hydrodynamics of interfacial vortex recapture remains unexplored. We investigate interfacial (on water) vortical hydrodynamics in Microvelia americana, one of the smallest and fastest water striders, skating at 50 body lengths per second (BL/s) or 15 cm/s. Their middle legs shed counter-rotating vortices, re-energized by their hind legs, demonstrating interfacial vortex recapture. High-speed imaging, particle imaging velocimetry, physical models, and CFD simulations show re-energization increases thrust by creating positive pressure at the hind tarsi, acting as a virtual wall. This vortex capture is facilitated by the tripod gait, leg morphology, and precise spatio-temporal placement of the hind tarsi during the power stroke. Our study extends vortex recapture principles from bulk fluids to the interface, offering insights into efficient interfacial locomotion, where surface tension and capillary waves challenge movement. Understanding interfacial vortex hydrodynamics can guide the development of energy-efficient microrobots to explore the planets water surface niches, critical frontlines of climate change and pollution. Significance StatementInterfacial Vortex Recapture in Microvelia americana extends the vortex recapture principles to the air-water interface, revealing an efficient locomotory mode in a challenging ecological niche. By demonstrating thrust enhancement through precise vortex interactions, our study bridges biology and fluid dynamics. This discovery informs the design of energy-efficient amphibious microrobots, capable of navigating the water interface with a new tripod gait paradigm, diverging from the conventional drag-based rowing designs. These findings are foundational for exploring and monitoring the water surface, an ecological interface vital for addressing climate change and pollution impacts.

biophysics↗

bioRxiv2024

Tiny amphibious insects use tripod gait for seamless transition across land, water, and duckweed

Insects exhibit remarkable adaptability in their locomotive strategies across diverse environments, a crucial trait for foraging, survival, and predator avoidance. Microvelia, tiny 2-3 mm insects that adeptly walk on water surfaces, exemplify this adaptability by using the alternating tripod gait in both aquatic and terrestrial terrains. These insects commonly inhabit low-flow ponds and streams cluttered with natural debris like leaves, twigs, and duckweed. Using high-speed imaging and pose-estimation software, we analyze Microvelia spp.s movement across water, sandpaper (simulating land), and varying duckweed densities (10%, 25%, and 50% coverage). Our results reveal Microvelia maintain consistent joint angles and strides of their upper and hind legs across all duckweed coverages, mirroring those seen on sandpaper. Microvelia adjust the stride length of their middle legs based on the amount of duckweed present, decreasing with increased duckweed coverage and at 50% duckweed coverage, their middle legs strides closely mimic their strides on sandpaper. Notably, Microvelia achieve speeds up to 56 body lengths per second on water, nearly double those observed on sandpaper and duckweed (both rough, frictional surfaces), highlighting their higher speeds on low friction surfaces such as the waters surface. This study highlights Microvelias ecological adaptability, setting the stage for advancements in amphibious robotics that emulate their unique tripod gait for navigating complex terrains.

animal behavior and cognition↗

bioRxiv2024

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

The air-water of the planets water bodies, such as ponds, lakes and streams, presents an uncertain ecological niche with predatory threats from above and below. As Microvelia move 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 the Microvelias ability to walk on water. Removal of both hind tarsi causes Microvelia spp. to rock their bodies (yaw) while running across the water surface at {+/-}19{degrees}, compared to {+/-}7{degrees} in non-ablated specimens. This increase in yaw, resulting from the removal of hind tarsi, indicates that Microvelia use their hind legs as rudders to regulate yaw, originating from the contralateral middle legs strokes on the waters surface through an alternating tripod gait. Ablation of the ipsilateral middle and hind tarsi disrupts directionality, making Microvelia turn in the direction of their intact limbs. This loss of directionality does not occur with the removal of contralateral middle and hind tarsi. However, Microvelia lose their ability to use the alternating tripod gait to walk for water walking on the day of contralateral ablation. Remarkably, by the next day Microvelia adapt 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 of Microvelia 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.

animal behavior and cognition↗