Wet webs work better: Humidity, supercontraction and the performance of spider orb webs

Boutry, Cecilia; Blackledge, Todd A.

doi:10.1242/jeb.084236

Cited by 32 publications

(26 citation statements)

References 41 publications

(65 reference statements)

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“…Changes in humidity over the course of a day affect the web's ability to both withstand prey impact and retain intercepted prey. Webs of Argiope trifasciata and Nephila clavipes were better able to absorb the kinetic energy of simulated prey strikes at high humidity than at low humidity (Boutry and Blackledge, 2013). Our study demonstrates that fine-scale, humidity-mediated changes in capture thread droplet adhesion affect prey retention times.…”

Section: Discussionmentioning

confidence: 68%

Humidity-mediated changes in an orb spider's glycoprotein adhesive impact prey retention time

Opell

Buccella

Godwin

et al. 2017

Journal of Experimental Biology

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Properties of the viscous prey capture threads of araneoid orb spiders change in response to their environment. Relative humidity (RH) affects the performance of the thread's hygroscopic droplets by altering the viscoelasticity of each droplet's adhesive glycoprotein core. Studies that have characterized this performance used smooth glass and steel surfaces and uniform forces. In this study, we tested the hypothesis that these changes in performance translate into differences in prey retention times. We first characterized the glycoprotein contact surface areas and maximum extension lengths of Araneus marmoreus droplets at 20%, 37%, 55%, 72% and 90% RH and then modeled the relative work required to initiate pull-off of a 4 mm thread span, concluding that this species' droplets and threads performed optimally at 72% RH. Next, we evaluated the ability of three equally spaced capture thread strands to retain a house fly at 37%, 55% and 72% RH. Each fly's struggle was captured in a video and bouts of active escape behavior were summed. House flies were retained 11 s longer at 72% RH than at 37% and 55% RH. This difference is ecologically significant because the short time after an insect strikes a web and before a spider begins wrapping it is an insect's only opportunity to escape from the web. Moreover, these results validate the mechanism by which natural selection can tune the performance of an orb spider's capture threads to the humidity of its habitat.

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Section: Discussionmentioning

confidence: 68%

Humidity-mediated changes in an orb spider's glycoprotein adhesive impact prey retention time

Opell

Buccella

Godwin

et al. 2017

Journal of Experimental Biology

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“…Supercontraction will also affect transverse wave propagation, even though a change in modulus does not ( figure 4c,d ). Supercontraction has been shown to generate stresses of around 50 MPa when constrained [46 -48] and this 'supercontraction stress' is thought to increase stress in radial threads following supercontraction to prevent sagging [45,47,49,50], which will increase the speed and amplitude of transverse waves (table 1).…”

Section: Longitudinal Waves and Modulusmentioning

confidence: 99%

Tuning the instrument: sonic properties in the spider's web

Mortimer

Soler

Siviour

et al. 2016

J. R. Soc. Interface.

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Spider orb webs are multifunctional, acting to absorb prey impact energy and transmit vibratory information to the spider. This paper explores the links between silk material properties, propagation of vibrations within webs and the ability of the spider to control and balance web function. Combining experimental and modelling approaches, we contrast transverse and longitudinal wave propagation in the web. It emerged that both transverse and longitudinal wave amplitude in the web can be adjusted through changes in web tension and dragline silk stiffness, i.e. properties that can be controlled by the spider. In particular, we propose that dragline silk supercontraction may have evolved as a control mechanism for these multifunctional fibres. The various degrees of active influence on web engineering reveals the extraordinary ability of spiders to shape the physical properties of their self-made materials and architectures to affect biological functionality, balancing trade-offs between structural and sensory functions.

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“…The covering of the axial threads with the aqueous glue causes the flagelliform silk to considerably shrink and increase in extensibility. This enables the kinetic energy of impacting prey to be imparted onto the web, reducing the probability of the prey bouncing off the web [24], [25]. The mechanical properties of spiral and gumfoot threads differ, most likely as a consequence of the different properties of the respective axial silks [19], [26]–[28], although differences in the biochemistries of the glues may also play a role [29].…”

Section: Introductionmentioning

confidence: 99%

Nutrient Deprivation Induces Property Variations in Spider Gluey Silk

et al. 2014

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Understanding the mechanisms facilitating property variability in biological adhesives may promote biomimetic innovations. Spider gluey silks such as the spiral threads in orb webs and the gumfoot threads in cobwebs, both of which comprise of an axial thread coated by glue, are biological adhesives that have variable physical and chemical properties. Studies show that the physical and chemical properties of orb web gluey threads change when spiders are deprived of food. It is, however, unknown whether gumfoot threads undergo similar property variations when under nutritional stress. Here we tested whether protein deprivation induces similar variations in spiral and gumfoot thread morphology and stickiness. We manipulated protein intake for the orb web spider Nephila clavipes and the cobweb spider Latrodectus hesperus and measured the diameter, glue droplet volume, number of droplets per mm, axial thread width, thread stickiness and adhesive energy of their gluey silks. We found that the gluey silks of both species were stickier when the spiders were deprived of protein than when the spiders were fed protein. In N. clavipes a concomitant increase in glue droplet volume was found. Load-extension curves showed that protein deprivation induced glue property variations independent of the axial thread extensions in both species. We predicted that changes in salt composition of the glues were primarily responsible for the changes in stickiness of the silks, although changes in axial thread properties might also contribute. We, additionally, showed that N. clavipes' glue changes color under protein deprivation, probably as a consequence of changes to its biochemical composition.

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Wet webs work better: Humidity, supercontraction and the performance of spider orb webs

Cited by 32 publications

References 41 publications

Humidity-mediated changes in an orb spider's glycoprotein adhesive impact prey retention time

Humidity-mediated changes in an orb spider's glycoprotein adhesive impact prey retention time

Tuning the instrument: sonic properties in the spider's web

Nutrient Deprivation Induces Property Variations in Spider Gluey Silk

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