Thorny devil water transport figure S3 from Adsorption and movement of water by skin of the Australian thorny devil (Agamidae: Moloch horridus) (original) (raw)
Related papers
Adsorption and movement of water by skin of the Australian thorny devil (Agamidae: Moloch horridus )
Royal Society Open Science, 2017
Moisture-harvesting lizards, such as the Australian thorny devil Moloch horridus , have remarkable adaptations for inhabiting arid regions. Their microstructured skin surface, with channels in between overlapping scales, enables them to collect water by capillarity and passively transport it to the mouth for ingestion. We characterized this capillary water transport for live thorny devils using high-speed video analyses. Comparison with preserved specimens showed that live lizards are required for detailed studies of skin water transport. For thorny devils, there was no directionality in cutaneous water transport (unlike Phrynosoma ) as 7 µl water droplets applied to the skin were transported radially over more than 9.2 mm. We calculated the total capillary volume as 5.76 µl cm −2 (dorsal) and 4.45 µl cm −2 (ventral), which is reduced to 50% filling by the time transportation ceases. Using micro-computed tomography and scanning electron microscopy of shed skin to investigate capilla...
Cutaneous water collection by a moisture-harvesting lizard, the thorny devil (Moloch horridus)
The Journal of experimental biology, 2016
Moisture-harvesting lizards, such as the Australian thorny devil, Moloch horridus, have the remarkable ability to inhabit arid regions. Special skin structures, comprising a micro-structured surface with capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and transport it to the mouth for ingestion. The ecological role of this mechanism is the acquisition of water from various possible sources such as rainfall, puddles, dew, condensation on the skin, or absorption from moist sand, and we evaluate here the potential of these various sources for water uptake by M. horridus The water volume required to fill the skin capillary system is 3.19% of body mass. Thorny devils standing in water can fill their capillary system and then drink from this water, at approximately 0.7 µl per jaw movement. Thorny devils standing on nearly saturated moist sand could only fill the capillary channels to 59% of their capacity, and did not drink. Ho...
Water and energy balance of the thorny devil Moloch horridus: is the devil a sloth?
Amphibia-Reptilia, 1995
Rates of turnover of water, energy and sodium were measured for free-ranging thorny devils (Moloch horridus), which are myrmecophagous agamid lizards, in a semi-arid Western Australian habitat. There were significant differences in body water content and water turnover rate (WTR) measurements for cool, wet, average and hot periods, although the field metabolic rate (FMR) and sodium turnover (NaTR) rate did not differ significantly between weather conditions. The thorny devil had a substantially lower field WTR during dry periods (10-15 ml kg-1 d-1) than expected for semi-arid and arid lizards, although the WTR was higher in wet conditions (30-35 ml kg-1 d-1). The field metabolic rate of thorny devils (0.134 ml CO2 g-1 h-1) was only slightly less than that expected for a semi-arid/lizard (0.178 ml CO2 g-1 h-1), despite the apparently slothful nature of the thorny devil. The sodium turnover rate of the thorny devil (1.5-2.5 mmol kg-1 d-1) was within the range reported for other semi-a...
Freshwater Biology, 1993
1. Drag coefficients of cylindrical-case caddis iarvae from running waters were investigated in the laboratory using an artificial stream channel. 2. Dead Iarvae of the limnephilids AUogamus auricollis (first to fifth instars), fifth instars of Potamophylax cingulatus, Chaetopteryx fusca, Drusus monticola, Metanoea rhaetica and fourth instars of the brachycentrid Micrasema minimum, were exposed to different current speeds. When the heads of the larvae were directed towards the water flow (frontal position), the current necessary to dislodge the larvae ranged from 3.00cms"' (A. auricollis, first instar) to 70.50cms"' (P. cingulatus). With flow normal to the long axis of the case (lateral position), these speeds ranged from 2.20cms"' (M. minimum) to 20.80cms"' (P. cingulatus). 3. In frontal position, individual Reynolds numbers at the moment of dislodgement ranged from 74 {A. auricollis, first instars) to 14100 (P. cingulatus), and from 14 (M. minimum) to 1143 (P. cingulatus) in lateral position. Regression equations correlating case length, mean case width or fresh weight with Reynolds numbers at the moment of dislodgement (frontal and lateral position) were very highly significant with r^ 5^ 0.91. 4. For the range of Reynolds numbers given above, the drag coefficient varied between 5.05 (A. auricollis, first instars) and 0.26 (P. cingulatus) in frontal case position and from 2.97 (M. minimutn) to 0.69 (C, fusca) in lateral case position. Furthermore, the relationship between Reynolds number and drag coefficient was found to be linear on a In/ln scale for both frontal and lateral case position.
The Integument of Water-walking Arthropods: Form and Function
Advances in Insect Physiology, 2007
We develop a coherent view of the form and function of the integument of water-walking insects and spiders by reviewing biological work on the subject in light of recent advances in surface science. Particular attention is given to understanding the complex nature of the interaction between water-walking arthropods and the air-water surface. We begin with a discussion of the fundamental principles of surface tension and the wetting of a solid by a fluid. These basic concepts are applied to rationalize the form of various body parts of water-walking arthropods according to their function. Particular attention is given to the influence of surface roughness on water-repellency, a critical feature of water-walkers that enables them to avoid entrapment at the interface, survive the impact of raindrops and breathe if submerged. The dynamic roles of specific surface features in thrust generation, drag reduction and anchoring on the free surface are considered. New imaging techniques that promise important insights into this class of problems are discussed. Finally, we highlight the interplay between the biology, physics and engineering communities responsible for the rapid recent advances in the biomimetic design of smart, waterrepellent surfaces.
Fluid and particle passage in three duiker species
European Journal of Wildlife Research, 2011
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Liquid dispensing in the adhesive hairy pads of dock beetles
Journal of The Royal Society Interface, 2020
Many insects can climb on smooth inverted substrates using adhesive hairy pads on their legs. The hair–surface contact is often mediated by minute volumes of liquid, which form capillary bridges in the contact zones and aid in adhesion. The liquid transport to the contact zones is poorly understood. We investigated the dynamics of liquid secretion in the dock beetleGastrophysa viridulaby quantifying the volume of the deposited liquid footprints during simulated walking experiments. The footprint volume increased with pad–surface contact time and was independent of the non-contact time. Furthermore, the footprint volume decreased to zero after reaching a threshold cumulative volume (approx. 30 fl) in successive steps. This suggests a limited reservoir with low liquid influx. We modelled our results as a fluidic resistive system and estimated the hydraulic resistance of a single attachment hair of the order of MPa · s/fl. The liquid secretion in beetle hairy pads is dominated by passi...
The hydrodynamics of water-walking arthropods
2010
We present the results of a combined experimental and theoretical investigation of the dynamics of water-walking insects and spiders. Using high-speed videography, we describe their numerous gaits, some analogous to those of their terrestrial counterparts, others specialized for life at the interface. The critical role of the rough surface of these water walkers in both floatation and propulsion is demonstrated. Their waxy, hairy surface ensures that their legs remain in a water-repellent state, that the bulk of their leg is not wetted, but rather contact with the water arises exclusively through individual hairs. Maintaining this water-repellent state requires that the speed of their driving legs does not exceed a critical wetting speed. Flow visualization reveals that the wakes of most water walkers are characterized by a series of coherent subsurface vortices shed by the driving stroke. A theoretical framework is developed in order to describe the propulsion in terms of the transfer of forces and momentum between the creature and its environment. The application of the conservation of momentum to biolocomotion at the interface confirms that the propulsion of water walkers may be rationalized in terms of the subsurface flows generated by their driving stroke. The two principal modes of propulsion available to small water walkers are elucidated. At driving leg speeds in excess of the capillary wave speed, macroscopic curvature forces are generated by deforming the meniscus, and the surface behaves effectively as a trampoline. For slower speeds, the driving legs need not substantially deform the surface but may instead simply brush it: the resulting contact or viscous forces acting on the leg hairs crossing the interface serve to propel the creature forward.