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Full-Text Articles in Life Sciences
Spider Silk: A Brief Review And Prospectus On Research Linking Biomechanics And Ecology In Draglines And Orb Webs, Todd Blackledge
Spider Silk: A Brief Review And Prospectus On Research Linking Biomechanics And Ecology In Draglines And Orb Webs, Todd Blackledge
Todd A. Blackledge
Spiders construct a wide variety of silk structures, ranging from draglines to prey capture webs. Spider silks rank among the toughest materials known to science, and these material properties are critical for understanding how silk structures, such as webs, function. However, the mechanics of spider silk are often ignored in the study of webs. This review aims to show how the material properties of silk proteins, the structural properties of silk threads, and the architectures of webs ultimately interact to determine the function of orb webs during prey capture. I first provide a brief introduction into spider silk and how …
Unraveling The Mechanical Properties Of Composite Silk Threads Spun By Cribellate Orb-Weaving Spiders, Todd Blackledge, Cheryl Hayashi
Unraveling The Mechanical Properties Of Composite Silk Threads Spun By Cribellate Orb-Weaving Spiders, Todd Blackledge, Cheryl Hayashi
Todd A. Blackledge
Orb-web weaving spiders depend upon the mechanical performance of capture threads to absorb the energy of flying prey. Most orb-weavers spin wet capture threads with core fibers of flagelliform silk. These threads are extremely compliant and extensible due to the folding of their constituent proteins into molecular nanosprings and hydration by a surrounding coating of aqueous glue. In contrast, other orb-weavers use cribellate capture threads, which are composite structures consisting of core fibers of pseudoflagelliform silk surrounded by a matrix of fine dry cribellar fibrils. Based on phylogenetic evidence, cribellate capture threads predate the use of viscid capture threads. To …
Can A Spider Web Be Too Sticky? Tensile Mechanics Constrains The Evolution Of Capture Spiral Stickiness In Orb-Weaving Spiders, Todd Blackledge, Ingi Agnarsson
Can A Spider Web Be Too Sticky? Tensile Mechanics Constrains The Evolution Of Capture Spiral Stickiness In Orb-Weaving Spiders, Todd Blackledge, Ingi Agnarsson
Todd A. Blackledge
Orb-weaving spiders rely on sticky capture threads to retain prey long enough to be located and attacked. The evolution of viscid silk is associated with the high diversity of araneoid orb-weaving spiders, in part because it is cheaper to produce than the primitive dry cribellate fibrous adhesive used by deinopoid orb-weaving spiders. Unlike cribellate threads, viscid glue contributes little to the tensile strength of the capture spiral it decorates. However, viscid silk utilizes a unique suspension bridge mechanism, absent in cribellate silk, which increases total stickiness by recruiting the adhesion of multiple glue droplets. Here, we analyze the relationship between …
Polarized Light Microscopy, Variability In Spider Silk Diameters, And The Mechanical Characterization Of Spider Silk, Todd Blackledge, Richard Cardullo, Cheryl Hayashi
Polarized Light Microscopy, Variability In Spider Silk Diameters, And The Mechanical Characterization Of Spider Silk, Todd Blackledge, Richard Cardullo, Cheryl Hayashi
Todd A. Blackledge
Spider silks possess a remarkable combination of high tensile strength and extensibility that makes them among the toughest materials known. Despite the potential exploitation of these properties in biotechnology, very few silks have ever been characterized mechanically. This is due in part to the difficulty of measuring the thin diameters of silk fibers. The largest silk fibers are only 5–10 μm in diameter and some can be as fine as 50 nm in diameter. Such narrow diameters, coupled with the refraction of light due to the anisotropic nature of crystalline regions within silk fibers, make it difficult to determine the …
Convergent Evolution Of Behavior In An Adaptive Radiation Of Hawaiian Web-Building Spiders, Todd Blackledge, Rosemary Gillespie
Convergent Evolution Of Behavior In An Adaptive Radiation Of Hawaiian Web-Building Spiders, Todd Blackledge, Rosemary Gillespie
Todd A. Blackledge
Species in ecologically similar habitats often display patterns of divergence that are strikingly comparable, suggesting that natural selection can lead to predictable evolutionary change in communities. However, the relative importance of selection as an agent mediating in situ diversification, versus dispersal between habitats, cannot be addressed without knowledge of phylogenetic history. We used an adaptive radiation of spiders within the Hawaiian Islands to test the prediction that species of spiders on different islands would independently evolve webs with similar architectures. Tetragnatha spiders are the only nocturnal orb-weaving spiders endemic to the Hawaiian archipelago, and multiple species of orb-weaving Tetragnatha co-occur …
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 …
Post-Secretion Processing Influences Spider Silk Performance, Todd Blackledge, Sean Blamires, Chun-Lin Wu, I-Min Tso
Post-Secretion Processing Influences Spider Silk Performance, Todd Blackledge, Sean Blamires, Chun-Lin Wu, I-Min Tso
Todd A. Blackledge
Phenotypic variation facilitates adaptations to novel environments. Silk is an example of a highly variable biomaterial. The two-spidroin (MaSp) model suggests that spider major ampullate (MA) silk is composed of two proteins-MaSp1 predominately contains alanine and glycine and forms strength enhancing β-sheet crystals, while MaSp2 contains proline and forms elastic spirals. Nonetheless, mechanical properties can vary in spider silks without congruent amino acid compositional changes. We predicted that post-secretion processing causes variation in the mechanical performance of wild MA silk independent of protein composition or spinning speed across 10 species of spider. We used supercontraction to remove post-secretion effects and …
Reconstructing Web Evolution And Spider Diversification In The Molecular Era, Todd Blackledge, Nikolaj Scharff, Jonathan Coddington, Tamas Szuts
Reconstructing Web Evolution And Spider Diversification In The Molecular Era, Todd Blackledge, Nikolaj Scharff, Jonathan Coddington, Tamas Szuts
Todd A. Blackledge
The evolutionary diversification of spiders is attributed to spectacular innovations in silk. Spiders are unique in synthesizing many different kinds of silk, and using silk for a variety of ecological functions throughout their lives, particularly to make prey-catching webs. Here, we construct a broad higher-level phylogeny of spiders combining molecular data with traditional morphological and behavioral characters. We use this phylogeny to test the hypothesis that the spider orb web evolved only once. We then examine spider diversification in relation to different web architectures and silk use. We find strong support for a single origin of orb webs, implying a …
The Phylogenetic Placement Of Psechridae Within Entelegynae And The Convergent Origin Of Orb-Like Webs, Todd Blackledge, Matjaz Gregoric, Matjaz Kuntner, Ingi Agnarsson
The Phylogenetic Placement Of Psechridae Within Entelegynae And The Convergent Origin Of Orb-Like Webs, Todd Blackledge, Matjaz Gregoric, Matjaz Kuntner, Ingi Agnarsson
Todd A. Blackledge
Evolutionary convergence of phenotypic traits provides evidence for their functional success. The origin of the orb web was a critical event in the diversification of spiders that facilitated a spectacular radiation of approximately 12 000 species and promoted the evolution of novel web types. How the orb web evolved from ancestral web types, and how many times orb-like architectures evolved in spiders, has been debated for a long time. The little known spider genus Fecenia (Psechridae) constructs a web that resembles the archetypical orb web, but morphological data suggest that Psechridae (Psechrus + Fecenia) does not belong in Orbiculariae, the …