Web spiders

Arañas Espinosas, Araneidae, Distribución, Lista de Especies, Colombia as arañas espinosas del género Micrathena constituyen elementos comunes y conspicuos de la mayoría de los bosques y paisajes en las diversas regiones geográficas de Colombia. Las hembras de este género están provistas de recubrimientos esclerosados en la región abdominal, los cuales se proyectan lateral y/o posteriormente a manera de espinas que pueden ser simples, lobuladas o bifurcadas; generalmente exhiben coloraciones vistosas y construyen elaboradas telas orbiculares dispuestas en sentido vertical, con el centro vacío. Estas arañas son de hábitos diurnos y permanecen sedentarias la mayor parte del tiempo en el centro de la tela, esperando la caída de presas, con el cefalotórax orientado hacia abajo. Los machos son de tamaños menores que las hembras y presentan una morfología muy diferente, con el abdomen sub-rectangular o cuadrangular y con espinas cortas. Algunas especies presentan machos miméticos de hormigas.

We investigated how vegetation features and temporal variation influenced web spider richness, abundance and composition along an edge between Araucaria forest and pasture in southern Brazil. Web spiders and vegetation were surveyed four times over a 1-year period, in five 5 Â 5 m plots randomised in four locations: 50 m into the pasture, 0, 50 and 250 m into the forest. We collected a total of 836 web spiders (33 morphospecies and six families). We found different web spider assemblages occurring at the pasture edge and forest interior. The richness and abundance of web spiders decreased up to 50 m towards the forest interior in all seasons, and we found a positive influence of vegetation richness on web spider abundance. In conclusion, web spider assemblages are influenced by an edge gradient, this pattern is consistent throughout the year and is strongly related to vegetation features.

ABSTRACT. Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the ...

The species classically grouped in the genus Zygiella F.O. Pickard-Cambridge 1902 are thought to all possess a characteristic orb web feature-a spiral-free sector in the upper part of the orb. Zygiella s.l. has recently been split into four genera, Zygiella s.s., Leviellus Wunderlich 2004, Parazygiella Wunderlich 2004 and Stroemiellus Wunderlich 2004, and proposed to belong to family Zygiellidae, rather than the classical Araneidae. To find orb web features that could potentially diagnose these species and/or genera, we investigated female web architectures of L. thorelli, P. montana, S. stroemi, Z. keyserlingi and Z. x-notata. We investigated a total of 278 female webs and compared 16 characters emphasizing web size, web and hub asymmetry, as well as radial and spiral counts. The free sector may be present in all species but its prevalence in female webs varied from 41% in Z. keyserlingi to 94% in P. montana. Various combinations of web architecture characters may diagnose those species that in our sample represented all four genera: Zygiella s.s. may be diagnosed by the median number of non-circulating sticky spirals below hub, Stroemiellus by the small web size with small mesh width and the non-circulating spirals above hub, Parazygiella by few primary radii and sticky spirals, and Leviellus by a pronounced vertical hub displacement. This suite of diagnostic features may provide preliminary support for the current taxonomy of Zygiella s.l., although the ultimate test, i.e., a phylogeny, is needed to test the validity of the genera. Seven out of 16 web characters are potentially phylogenetically informative because they show a statistically significant shared variation among species. Our study, which pioneers the quantification of web data to distinguish species, implies that the interspecific variation in webs may turn out to reflect phylogenetic relationships among Zygiella s.l. Many studies show that behavioral characters are taxo-nomically and phylogenetically useful (

PageRank (PR) algorithm ascertains the importance of web pages based on a PageRank metric. It          state that if a page has important links to it , its link to other pages also contribute to their importance and a page with high PageRank is most relevant page to be downloaded. An improved version of PageRank, WPR, assigns more value to more important pages instead of dividing the rank value of a page evenly among all its outgoing links whereas TR combats spam pages on World Wide Web and ultimately aims at improving the efficiency of search results. These two variations of PR (WPR and TR) gives an insight of hybrid formula that distribute rank score according to popularity of links as well as ensures the crawling of only trusted pages.

Characterized by distinctive evolutionary adaptations, spiders provide a comprehensive system for evolutionary and developmental studies of anatomical organs, including silk and venom production. Here we performed cDNA sequencing using massively parallel sequencers (454 GS-FLX Titanium) to generate ~80,000 reads from the spinning gland of Actinopus spp. (infraorder: Mygalomorphae) and Gasteracantha cancriformis (infraorder: Araneomorphae, Orbiculariae clade). Actinopus spp. retains primitive characteristics on web usage and presents a single undifferentiated spinning gland while the orbiculariae spiders have seven differentiated spinning glands and complex patterns of web usage. MIRA, Celera Assembler and CAP3 software were used to cluster NGS reads for each spider. CAP3 unigenes passed through a pipeline for automatic annotation, classification by biological function, and comparative transcriptomics. Genes related to spider silks were manually curated and analyzed. Although a single spidroin gene family was found in Actinopus spp., a vast repertoire of specialized spider silk proteins was encountered in orbiculariae. Astacin-like metalloproteases (meprin subfamily) were shown to be some of the most sampled unigenes and duplicated gene families in G. cancriformis since its evolutionary split from mygalomorphs. Our results confirm that the evolution of the molecular repertoire of silk proteins was accompanied by the (i) anatomical differentiation of spinning glands and (ii) behavioral complexification in the web usage. Finally, a phylogenetic tree was constructed to cluster most of the known spidroins in gene clades. This is the first large-scale, multi-organism transcriptome for spider spinning glands and a first step into a broad understanding of spider web systems biology and evolution.

Web search process can be time consuming and frustrating due to the enormous amount of information available on the WWW. Recently web spiders with Information Extraction Techniques that analyze retrieved documents have been proposed. This leads to an extended search process in which hypertext structure is enriched with semantic annotations. As consequence graph visualization techniques must be up-to-date for a better understanding of modified results. In particular additional semantic information must be taken into account without forcing the user browsing through unnecessary documents. As a first attempt towards graph visualization for semantic crawling, in this work we describe an example of XML-based visualisation system that extends the notion of query maps and provides a semantic visualization by means of dynamic fields that are associated to each node.

Web search process can be time consuming and frustrating due to the enormous amount of information available on the Web. Recently, Web spiders with information extraction techniques that analyze retrieved documents have been proposed. This leads to an extended search process in which hypertext structure is enriched with semantic annotations. As consequence graph visualization techniques must be up-to-date for a better understanding of modified results. In particular additional semantic information must be taken into account without forcing the user browsing through unnecessary documents. As a first attempt towards graph visualization for semantic crawling, in this work we describe an example of XML-based visualisation system that provides a semantic visualization by means of dynamic fields that are associated to each node.

Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the production of new biomaterials. During the evolution of spider species, complex behaviors of web production and usage have been coupled with anatomical specialization of spinning glands. Spiders retaining ancestral characters, such as the ones belonging to the Mygalomorph group, present simpler sorts of webs used mainly to build burrows and egg sacs, and their silks are produced by globular undifferentiated spinning glands. In contrast, Araneomorphae spiders have a complex spinning apparatus, presenting up to seven morphologically distinct glands, capable to produce a more complex set of silk polymers with different degrees of rigidness and elasticity associated with distinct behaviors. Aiming to provide a discussion involving a number of spider silks’ biological aspects, in this review we present descriptions of members from each family of spidroin identified from five spider species of the Brazilian biodiversity, and an evolutionary study of them in correlation with the anatomical specialization of glands and spider’s spinning behaviors. Due to the biotechnological importance of spider silks for the production of new biomaterials, we also discuss about the new possible technical and biomedical applications of spider silks and the current status of it.