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Full-Text Articles in Life Sciences
Darwin's Bark Spider: Giant Prey In Giant Orb Webs (Araneidae: Caerostris Darwini), Todd Blackledge, Matjaz Gregoric, Ingi Agnarsson, Matjaz Kuntner
Darwin's Bark Spider: Giant Prey In Giant Orb Webs (Araneidae: Caerostris Darwini), Todd Blackledge, Matjaz Gregoric, Ingi Agnarsson, Matjaz Kuntner
Todd A. Blackledge
Although the diversity of spider orb web architectures is impressive, few lineages have evolved orb webs larger than lm in diameter. Until recently, such web gigantism was reported only in a few nephilids and araneids. However, new studies on bark spiders (Caerostris) of Madagascar report a unique case of web gigantism: Darwin's bark spider (C. darwini) casts its webs over substantial water bodies, and these webs are made from silk whose toughness outperforms all other known spider silks. Here we investigate C darwini web architecture and provide data to begin to answer two intriguing questions to explain these extraordinary web …
Darwin's Bark Spider: Giant Prey In Giant Orb Webs (Caerostris Darwini, Araneae: Araneidae), Todd Blackledge, Matjaz Gregoric, Ingi Agnarsson, Matjaz Kuntner
Darwin's Bark Spider: Giant Prey In Giant Orb Webs (Caerostris Darwini, Araneae: Araneidae), Todd Blackledge, Matjaz Gregoric, Ingi Agnarsson, Matjaz Kuntner
Todd A. Blackledge
Although the diversity of spider orb web architectures is impressive, few lineages have evolved orb webs larger than 1m in diameter. Until recently, such web gigantism was reported only in a few nephilids and araneids. However, new studies on bark spiders (Caerostris) of Madagascar report a unique case of web gigantism: Darwin’s bark spider (C. darwini) casts its webs over substantial water bodies, and these webs are made from silk whose toughness outperforms all other known spider silks. Here we investigate C. darwini web architecture and provide data to begin to answer two intriguing questions to explain these extraordinary web …
Functionally Independent Components Of Prey Capture Are Architecturally Constrained In Spider Orb Webs, Todd Blackledge, Chad Eliason
Functionally Independent Components Of Prey Capture Are Architecturally Constrained In Spider Orb Webs, Todd Blackledge, Chad Eliason
Todd A. Blackledge
Evolutionary conflict in trait performance under different ecological contexts is common, but may also arise from functional coupling between traits operating within the same context. Orb webs first intercept and then retain insects long enough to be attacked by spiders. Improving either function increases prey capture and they are largely determined by different aspects of web architecture. We manipulated the mesh width of orbs to investigate its effect, along with web size, on prey capture by spiders and found that they functioned independently. Probability of prey capture increased with web size but was not affected by mesh width. Conversely, spiders …
Signal Conflict In Spider Webs Driven By Predators And Prey, Todd Blackledge
Signal Conflict In Spider Webs Driven By Predators And Prey, Todd Blackledge
Todd A. Blackledge
Variation in the sensory physiologies of organisms can bias the receptions of signals, driving the direction of signal evolution. Sensory drive in the evolution of signals may be particularly important for organisms that confront trade-offs in signal design between the need for conspicuousness to allow effective transfer of information and the need for crypsis of the signal to unintended receivers. Several genera of orb-weaving spiders include conspicuous silk designs, stabilimenta, in the centre of their webs. Stabilimenta can be highly visible signals to predators, warning them of the presence of a noxious, sticky silk web. However, stabilimenta can also be …
Behavioral And Biomaterial Coevolution In Spider Orb Webs, Todd Blackledge, Andrew Sensenig, Ingi Agnarsson
Behavioral And Biomaterial Coevolution In Spider Orb Webs, Todd Blackledge, Andrew Sensenig, Ingi Agnarsson
Todd A. Blackledge
Mechanical performance of biological structures, such as tendons, byssal threads, muscles, and spider webs, is determined by a complex interplay between material quality (intrinsic material properties, larger scale morphology) and proximate behaviour. Spider orb webs are a system in which fibrous biomaterials--silks--are arranged in a complex design resulting from stereotypical behavioural patterns, to produce effective energy absorbing traps for flying prey. Orb webs show an impressive range of designs, some effective at capturing tiny insects such as midges, others that can occasionally stop even small birds. Here, we test whether material quality and behaviour (web design) co-evolve to fine-tune web …
Do Stabilimenta In Orb Webs Attract Prey Or Defend Spiders?, Todd Blackledge, John Wenzel
Do Stabilimenta In Orb Webs Attract Prey Or Defend Spiders?, Todd Blackledge, John Wenzel
Todd A. Blackledge
Orb-weaving spiders are ideal organisms for the study of conflict between behavioral investments in foraging and defense because their webs provide physical manifestations of those investments. We examined the impact of including stabilimenta, designs of bright-white noncapture silk, at the center of orb webs for foraging and defense in Argiope aurantia. Our findings suggest that stabilimentum building is a defensive behavior, supporting the “web advertisement” hypothesis that the high visibility of stabilimenta can prevent birds from flying through webs. Yet, spiders often do not include stabilimenta in their webs, indicating that a serious cost is associated with them. We also …
Prey Capture As A Determinate Of Tangle Web Architecture In Dictyna Volucripes, Todd Blackledge, John Wenzel
Prey Capture As A Determinate Of Tangle Web Architecture In Dictyna Volucripes, Todd Blackledge, John Wenzel
Todd A. Blackledge
Foraging behaviors result from dynamic trade-offs made by organisms, incorporating factors such as past foraging success, reproductive effort, and predation risk. But, decision-making by animals occurs with incomplete information about the environment. We examined the relationship of web architecture and foraging decisions in the tangle web-building spider Dictyna volucripes Keyserling, a common spider in North American fields. Tangle webs are constructed over many days, which increases the total material and energetic investment in webs compared to orb-webs that are rebuilt daily. This reduces the profitability of changing web sites for tangle web spiders, making decisions about allocation of resources to …
State-Determinate Foraging Decisions And Web Architecture In The Spider Dictyna Volucripes (Araneae Dictynidae), Todd Blackledge, J Wenzel
State-Determinate Foraging Decisions And Web Architecture In The Spider Dictyna Volucripes (Araneae Dictynidae), Todd Blackledge, J Wenzel
Todd A. Blackledge
Foraging behaviors result from dynamic trade-offs made by organisms, incorporating factors such as past foraging success, reproductive effort, and predation risk. But, decision-making by animals occurs with incomplete information about the environment. We examined the relationship of web architecture and foraging decisions in the tangle web-building spider Dictyna volucripes Keyserling, a common spider in North American fields. Tangle webs are constructed over many days, which increases the total material and energetic investment in webs compared to orb-webs that are rebuilt daily. This reduces the profitability of changing web sites for tangle web spiders, making decisions about allocation of resources to …
Wet Webs Work Better: Humidity, Supercontraction And The Performance Of Spider Orb Webs, Todd Blackledge, Cecilia Boutry
Wet Webs Work Better: Humidity, Supercontraction And The Performance Of Spider Orb Webs, Todd Blackledge, Cecilia Boutry
Todd A. Blackledge
Like many biomaterials, spider silk responds to water through softening and swelling. Major ampullate silk, the main structural element of most prey capture webs, also shrinks dramatically if unrestrained or develops high tension if restrained, a phenomenon called ‘supercontraction’. While supercontraction has been investigated for over 30 years, its consequences for web performance remain controversial. Here, we measured prey capture performance of dry and wet (supercontracted) orb webs of Argiope and Nephila using small wood blocks as prey. Prey capture performance significantly increased at high humidity for Argiope while the improvement was less dramatic for Nephila. This difference is likely …
Are Three-Dimensional Spider Webs Defensive Adaptations?, Todd Blackledge, Jonathan Coddington, Rosemary Gillespie
Are Three-Dimensional Spider Webs Defensive Adaptations?, Todd Blackledge, Jonathan Coddington, Rosemary Gillespie
Todd A. Blackledge
Spider webs result from complex behaviours that have evolved under many selective pressures. Webs have been primarily considered to be foraging adaptations, neglecting the potential role of predation risk in the evolution of web architecture. The ecological success of spiders has been attributed to key innovations in how spiders use silk to capture prey, especially the invention of chemically adhesive aerial two-dimensional orb webs. However, araneoid sheet web weavers transformed the orb architecture into three-dimensional webs and are the dominant group of aerial web-building spiders world-wide, both in numbers and described species diversity. We argue that mud-dauber wasps are major …