Sequential origin in the high performance properties of spider dragline silk

Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers.

Identification and dynamics of polyglycine II nanocrystals in Argiope trifasciata flagelliform silk

Spider silks combine a significant number of desirable characteristics in one material, including large tensile strength and strain at breaking, biocompatibility, and the possibility of tailoring their properties. Major ampullate gland silk (MAS) is the most studied silk and their properties are explained by a double lattice of hydrogen bonds and elastomeric protein chains linked to polyalanine β-nanocrystals. However, many basic details regarding the relationship between composition, microstructure and properties in silks are still lacking. Here we show that this relationship can be traced in flagelliform silk (Flag) spun by Argiope trifasciata spiders after identifying a phase consisting of polyglycine II nanocrystals. The presence of this phase is consistent with the dominant presence of the –GGX– and –GPG– motifs in its sequence. In contrast to the passive role assigned to polyalanine nanocrystals in MAS, polyglycine II nanocrystals can undergo growing/collapse processes that contribute to increase toughness and justify the ability of Flag to supercontract.

The variability and interdependence of spider viscid line tensile properties

True stress-true strain curves of naturally spun viscid line fibers retrieved directly from the spiral of orb-webs built by Argiope trifasciata spiders were measured using a novel methodology. This new procedure combines a method for removing the aqueous coating of the fibers and a technique that allows the accurate measurement of their cross sectional area. Comparison of the tensile behaviour of different samples indicates that naturally spun viscid lines show a large variability, comparable to that of other silks, such as major ampullate gland silk and silkworm silk. Nevertheless, application of a statistical analysis allowed identifying two independent parameters that underlie the variability and characterize the observed range of true stress-true strain curves. Combination of this result with previous mechanical and microstructural data suggested the assignment of these two independent effects to the degree of alignment of the protein chains and to the local relative humidity which, in turn, depends on the composition of the viscous coating and on the external environmental conditions.

Caracterización de las Propiedades Dinámicas de la Seda de Araña

El término Biomimética se ha hecho común en los medios científicos, se refiere al trabajo de diversos científicos (ingenieros, químicos, físicos, biólogos, etc.) que tratan de copiar los procesos biológicos y aplicarlos en distintas áreas tecnológicas y científicas. En este campo científico, uno de los productos naturales que llama más la atención es la telaraña. Numerosos científicos en todo el mundo tratan de copiar las propiedades de la seda que produce la araña, y lo más interesante es que hasta intentan reproducir el método que usan las arañas para fabricar la seda De la bibliografía consultada, se desprende la importancia de la seda en la vida de las arañas, pues toda actividad que realizan tiene que ver de alguna manera con este elemento. Uno de estos elementos es la tela de araña orbicular, que representa el objeto principal para la supervivencia de la araña y su especie. Las investigaciones realizadas en esta línea nos proporcionan información sobre sus magníficas propiedades mecánicas como de resistencia, elasticidad y tenacidad del hilo de seguridad (seda MA) segregada por una araña de la especie Argiope Argentata. El enfoque de la presente tesis se realiza desde una perspectiva analítica-experimental, tomando a la tela de araña como una clase especial de sistemas pretensados, llamados Tensegrity Structures. Se desarrolla un modelo conceptual que describe en forma aproximada el comportamiento dinámico de una estructura hecha de seda MA. Haciendo uso de las técnicas experimentales de vibraciones libres se realizan los ensayos experimentales. La evaluación de los resultados analíticos y experimentales reflejan claramente que la función principal de la tela de araña es la de convertir energía cinética en energía de deformación y primordialmente en energía de disipación, el cual se efectúa gracias a las propiedades viscoelásticas de la seda. La araña en forma instintiva recurre a la ayuda del aire (como elemento disipador) para el buen funcionamiento de la tela de araña al momento de la captura de las presas, disipándose el 99% de la energía total en los tres primeros ciclos de oscilación de la tela de araña luego del impacto de la presa. ABSTRACT The term Biomimetic has become a very common word in the scientific world to describe the reproduction of the biological processes and its application in the different technogycal and scientific areas. One of the most notably natural product of this field is the Spiderweb. In the present days, many scientists of the world are active working in the reproduction of the proprieties of the Spiderweb. Most interesting even more, is the attempt to reproduce the process of the production of the Spiderweb by the spider. Most of the bibliography references deals whit the importance of the Spiderweb silk in the life of the spiders and the orbicular Spiderweb represents the spider survival and of the species. The research conducted in this field provide information about the excellent mechanical proprieties such us strength, elasticity and tenacity of the safety fiber (silk MA Drag-line) segregated by a spider of the Argiope Argentata species. The present work is oriented to an analytical and experimental study considering the Spiderweb as a special class of pre-stressed systems called Tensegrity (tensional integrity) structures. A conceptual model maked up by a cord und a point mass has been developed. This model approximates the dynamics performance of the structure made of the silk MA. The evaluation of the analytical and experimental results clear described that the main function of the Spiderweb is the transformation of the kinetic energy in deformation energy, and mainly in dissipation energy thank to the viscoelastic proprieties of the Spiderweb. With the help of the Spiderweb, the spider instinctively resorts to the help of the surroundings air as a dissipation element. This permits to dissipative the 99% of the total energy during the three first oscillations cycles of the web after the impact of the victim.

Desarrollo de un sistema de arañas inteligentes para la extracción de datos de empresas

El presente proyecto de fin de grado es uno de los resultados generados en un proyecto de financiación privada por parte de Telefónica consistente en el desarrollo y posterior implantación de un sistema para minería de datos de empresas presentes en Internet. Este TFG surge a partir de un proyecto que el grupo de investigación AICU-LABS (Mercator) de la UPM ha desarrollado para Telefónica, y tiene como elemento principal el desarrollo de Agentes web (también llamados robots software, “softbots” o “crawlers”) capaces de obtener datos de empresas a partir de sus CIF a través de internet. El listado de empresas nos los proporciona Telefónica, y está compuesto por empresas que no son clientes de Telefónica en la actualidad. Nuestra misión es proporcionarles los datos necesarios (principalmente teléfono, correo electrónico y dirección de la empresa) para la creación de una base de datos de potenciales clientes. Para llevar a cabo esta tarea, se ha realizado una aplicación que, a partir de los CIF que nos proporcionan, busque información en internet y extraiga aquella que nos interese. Además se han desarrollado sistemas de validación de datos para ayudarnos a descartar datos no válidos y clasificar los datos según su calidad para así maximizar la calidad de los datos producidos por el robot. La búsqueda de datos se hará tanto en bases de datos online como, en caso de localizarlas, las propias páginas web de las empresas. ABSTRACT This Final Degree Project is one of the results obtained from a project funded by Telefónica. This project consists on the development and subsequent implantation of a system which performs data mining on companies operating on the Internet. This document arises from a project the research group AICU-LABS (Mercator) from the Universidad Politécnica de Madrid has developed for Telefónica. The main goal of this project is the creation of web agents (also known as “crawlers” or “web spiders���) able to obtain data from businesses through the Internet, knowing only their VAT identification number. The list of companies is given by Telefónica, and it is composed by companies that are not Telefónica’s customers today. Our mission is to provide the data required (mainly phone, email and address of the company) to create a database of potential customers. To perform this task, we’ve developed an application that, starting with the given VAT numbers, searches the web for information and extracts the data sought. In addition, we have developed data validation systems, that are capable of discarding low quality data and also sorting the data according to their quality, to maximize the quality of the results produced by the robot. We’ll use both the companies’ websites and external databases as our sources of information.

Firefly “femmes fatales” acquire defensive steroids (lucibufagins) from their firefly prey

Female fireflies of the genus Photuris, the so-called firefly “femmes fatales,” prey on male fireflies of the genus Photinus. The females are able to entrap the males by faking the flash signal characteristics of the Photinus female. We found that by feeding on Photinus males, Photuris females gain more than nutrients. They also acquire defensive steroidal pyrones called lucibufagins, which are contained in Photinus but which Photuris fireflies are unable to produce on their own. Photuris females that eat Photinus males or lucibufagin are rejected by Phidippus jumping spiders. Lucibufagin itself proved to be a deterrent to such spiders. Field-collected Photuris females contain lucibufagin in varying amounts. The more lucibufagin they contain the more unacceptable they are to Phidippus.

Experimental evidence for a behavior-mediated trophic cascade in a terrestrial food chain

Predators of herbivorous animals can affect plant populations by altering herbivore density, behavior, or both. To test whether the indirect effect of predators on plants arises from density or behavioral responses in a herbivore population, we experimentally examined the dynamics of terrestrial food chains comprised of old field plants, leaf-chewing grasshoppers, and spider predators in Northeast Connecticut. To separate the effects of predators on herbivore density from the effects on herbivore behavior, we created two classes of spiders: (i) risk spiders that had their feeding mouth parts glued to render them incapable of killing prey and (ii) predator spiders that remained unmanipulated. We found that the effect of predators on plants resulted from predator-induced changes in herbivore behavior (shifts in activity time and diet selection) rather than from predator-induced changes in grasshopper density. Neither predator nor risk spiders had a significant effect on grasshopper density relative to a control. This demonstrates that the behavioral response of prey to predators can have a strong impact on the dynamics of terrestrial food chains. The results make a compelling case to examine behavioral as well as density effects in theoretical and empirical research on food chain dynamics.

Extraordinarily high spider densities on islands: flow of energy from the marine to terrestrial food webs and the absence of predation.

Some islands in the Gulf of California support very high densities of spiders. Spider density is negatively correlated with island size; many small islands support 50-200 spiders per m3 of cactus. Energy for these spiders comes primarily from the ocean and not from in situ productivity by land plants. We explicitly connect the marine and terrestrial systems to show that insular food webs represent one endpoint of the marine web. We describe two conduits for marine energy entering these islands: shore drift and seabird colonies. Both conduits are related to island area, having a much stronger effect on smaller islands. This asymmetric effect helps to explain the exceptionally high spider densities on small islands. Although productivity sets the maximal potential densities, predation (by scorpions) limits realized spider abundance. Thus, prey availability and predation act in concert to set insular spider abundance.

Book of monsters, by David and Marian Fairchild. Portraits and biographies of a few of the inhabitiants of woodland and meadow.

1914

The Cambridge natural history,

Vols. 1, 2, 5-7, 9 reprinted 1922; v. 3, 1927; and vols. 4, 8, 10, 1923.

Acariens ...

Cover-title.

[Attidae pamphlets]

Made up set; supplied title.

Memoire pour servir a commencer l'histoire des araignees aquatiques.

Mode of access: Internet.

Analytische Übersicht der europäischen Spinnenfamilien.

Mode of access: Internet.

La regénération des organes perdus chez les araignées.

Extract from Bulletin de la Société impériale des naturalistes de Moscou, 1887 (no.4).