Spider Research Articles

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Crowd-sourced biodiversity databases provide easy access to data and images for ecological education and research. One concern with using publicly sourced databases; however, is the quality of their images, taxonomic descriptions, and geographical metadata. The method presented in this paper attempts to address this concern using a suite of pipelines to evaluate taxonomic consistency, how well geo-tagging fits known distributions, and the image quality of crowd-sourced data acquired from iNaturalist, a crowd-sourced biodiversity database. Additionally, it provides researchers that use these datasets to report a quantifiable assessment of the taxonomic consistency. The pipeline allows users to analyze multiple images from iNaturalist and their associated metadata; to determine the level of taxonomic identification (family, genera, species) for each occurrence; whether the taxonomy label for an image matches accepted nesting of families, genera, and species; and whether geo-tags match the distribution of the taxon described using occurrence data from the Global Biodiversity Infrastructure Facility (GBIF) as a reference. Additionally, image quality is assessed using BRISQUE, an algorithm that allows for image quality evaluation without a reference photo. Entries from the order Araneae (spiders) are used as a case study. Overall, the results suggest that iNaturalist can provide large metadata and image sets for research. Given the inevitability of some low-quality observations, this pipeline provides a valuable resource for researchers and educators to evaluate the quality of iNaturalist and other crowd-sourced data.

Abundance and composition of arthropods in sugarcane (Saccharum officinarum) ecosystem

A short investigation was devised by Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore in 2022 to document the arthropod composition in sugarcane (Saccharum officinarum L.) ecosystem. Arthropod fauna was collected from sugarcane ecosystem in farmers’ field at Puthur of Coimbatore district, Tamil Nadu at weekly intervals. Totally, 2,310 individuals of the subclass Pterygota were collected and among them most of specimens belonged to Exopterygota. The exopterygota (1,029) were represented by 5 orders, viz. Hemiptera, Odonata, Orthoptera, Isoptera and Dermaptera. Majority of the individuals belonged to the family Aphididae (330) under the order Hemiptera. Under order Orthoptera, Gryllidae (46) was the dominant family closely followed by Acrididae (45). Among these, the dominant species was Gryllus spp. The order Odonata was represented by a single family Libellulidae (38) and the species was identified as Orthetrum sabina Drury, 1773. Under Endopterygota, 4 orders were identified and among these, Hymenoptera was the most common order with 740 numbers, followed by Diptera (237), Coleoptera (215) and Lepidoptera (89). Under the order Coleoptera, 3 families were recorded, with most of them falling under the family Coccinellidae (172) followed by Cicindelidae. Hymenopteran order comprised majorly of ants, belonging to the family Formicidae, of which 3 species were identified. Lepidoptera consisted of single species Ariadne merione Cramer, 1779 belonging to family Nymphalidae. Majority of Arachinda was represented by order Araneae. Under the order Araneae most of them pertained to families Araneidae, Lycosidae and Thomisidae. Neoscona sp., Hippasa sp., Pardosa sp. and Pardosa birmania Simon were found to be common in sugarcane ecosystem.

Characterization of two full-length tubuliform silk gene sequences from Neoscona theisi reveals intragenic concerted evolution and multiple copies in genome

Orb-web weaving spiders use a variety of silk types for particular tasks, and each silk type is composed of at least two spider silk proteins (spidroins). In the early stage of divergence, however, the molecular evolutionary processes act on spidroin variants are still unclear because of a lack of knowledge for full-length paralogous and orthologous gene sequences among closely related species. Here, we present two complete gene sequences encoding the tubuliform spidroin TuSp1 variants (TuSp1-v2 and TuSp1-v3) from orb-weaving spider Neoscona theisi. Both N. theisi TuSp1-v2 and TuSp1-v3 genes contain a single enormous exon (14,139 bp for TuSp1-v2 and 13,152 bp for TuSp1-v3) and dozens of tandemly arrayed repeats (25 repeats for TuSp1-v2 and 23 repeats for TuSp1-v3) with extreme intragenic homogenization. The pattern of expression for these two spidroins revealed that the level of TuSp1-v3 mRNA is ~3-fold higher than that of TuSp1-v2 in tubuliform gland. Phylogenetic analyses of spidroins not only show the occurrence of a gene duplication event for TuSp1-v2 and TuSp1-v3 in the common ancestor of the Neoscona and Araneus lineage but reinforce the role of concerted evolution for the extreme homogenization of TuSp1 repeats.

Five new species of the long-jawed orb-weaving spider genus Tetragnatha (Araneae, Tetragnathidae) in South America, with a key to the species from Argentina and Brazil

Five new species in the long-jawed orb-weaving spider genus Tetragnatha Latreille, 1804 are described from South America: Tetragnatha amazonicasp. nov. (Venezuela); T. cristatasp. nov. (Argentina and Brazil); T. didoratasp. nov. (Brazil); T. oncognathasp. nov. (Brazil); and T. pradoisp. nov. (Argentina and Brazil). A key to the 21 species of Tetragnatha from Argentina and Brazil is provided, completing the revision of the genus for these countries. The female of T. cladognatha Bertkau, 1880 is redescribed and a neotype is proposed, and its male is described for the first time. Additionally, we update the taxonomic status of the following six South American species: Tetragnatha labialis Nicolet, 1849 and T. americana Simon, 1896 are considered new junior synonymies of T. nitens (Audouin, 1826); and Tetragnatha bishopi Caporiacco, 1947, T. linearis Nicolet, 1849, T. similis Nicolet, 1849 and T. sternalis Nicolet, 1849 are proposed as nomina dubia due to missing or juvenile type-material.

The Orb-Weaving Spider Algorithm for Training of Recurrent Neural Networks

The quality of operation of neural networks in solving application problems is determined by the success of the stage of their training. The task of learning neural networks is a complex optimization task. Traditional learning algorithms have a number of disadvantages, such as «sticking» in local minimums and a low convergence rate. Modern approaches are based on solving the problems of adjusting the weights of neural networks using metaheuristic algorithms. Therefore, the problem of selecting the optimal set of values of algorithm parameters is important for solving application problems with symmetry properties. This paper studies the application of a new metaheuristic optimization algorithm for weights adjustment—the algorithm of the spiders-cycle, developed by the authors of this article. The approbation of the proposed approach is carried out to adjust the weights of recurrent neural networks used to solve the time series forecasting problem on the example of three different datasets. The results are compared with the results of neural networks trained by the algorithm of the reverse propagation of the error, as well as three other metaheuristic algorithms: particle swarm optimization, bats, and differential evolution. As performance criteria for the comparison of algorithms of global optimization, in this work, descriptive statistics for metrics of the estimation of quality of predictive models, as well as the number of calculations of the target function, are used. The values of the MSE and MAE metrics on the studied datasets were obtained by adjusting the weights of the neural networks using the cycling spider algorithm at 1.32, 25.48, 8.34 and 0.38, 2.18, 1.36, respectively. Compared to the inverse error propagation algorithm, the cycling spider algorithm reduced the value of the error metrics. According to the results of the study, it is concluded that the developed algorithm showed high results and, in the assessment of performance, was not inferior to the existing algorithm.

Adhesive contact and protein elastic modulus tune orb weaving spider glue droplet biomechanics to habitat humidity

Tiny glue droplets along the viscous capture threads of spider orb webs prevent insects from escaping. Each droplet is formed of a protein core surrounded by a hygroscopic aqueous layer, which cause the droplet's adhesion to change with humidity. As an insect struggles to escape the web, a thread's viscoelastic core proteins extend, transferring adhesive forces to the thread's support fibers. Maximum adhesive force is achieved when absorbed atmospheric moisture allows a flattened droplet to establish sufficient adhesive contact while maintaining the core protein cohesion necessary for force transfer. We examined the relationship between these droplet properties and adhesive force and the work of extending droplets at five relative humidities in twelve species that occupy habitats which have different humidities. A regression analysis that included both flattened droplet area and core protein elastic modulus described droplet adhesion, but the model was degraded when core protein area was substituted for droplet. Species from low humidity habitats expressed greater adhesion at lower humidities, whereas species from high humidity habitats expressed greater adhesion at high humidities. Our results suggest a general model of droplet adhesion with two adhesion peaks, one for low humidity species, which occurs when increasing droplet area and decreasing protein cohesion intersect, and another for high humidity species, which occurs when area and cohesion have diverged maximally. These dual peaks in adhesive force explain why some species from intermediate and high humidity habitats express high adhesion at several humidities. Statement of significanceWe characterized the effect of humidity on the adhesion of twelve orb weaving spider species’ glue droplets and showed how humidity-mediated changes in the contact area of a droplet’s outer, hygroscopic aqueous layer and the stiffness of its protein core affect droplet performance. This revealed how droplet adhesion has been tuned to the humidity of a species’ habitat and allowed us to revise a model that describes the environmental determinants of droplet biomechanics.

Frame line repair by the orb-weaver Micrathena duodecimspinosa (Araneae: Araneidae): possibly ancient behavior

Spider webs in general and orb webs in particular are delicate, ephemeral structures that are frequently damaged in nature. Some orb weavers respond to damage by quickly “shoring up” their webs with non-sticky dragline silk. This study of how Micrathena duodecimspinosa (O. Pickard-Cambridge, 1890) shores up damaged frame lines shows that repairs were largely based on a single, repeated pattern of attachments. These movements are shared with the distantly related family Pholcidae, suggesting a possibly ancient origin. Spiders tended to initiate repairs at the lower edge of a damaged sector, probably to reduce the damage produced when the spider's own weight caused sticky lines in slack portions of the web to sag into and adhere to each other. Repairs of lateral frames recuperated capture area more successfully than did those of upper frames, probably because damage caused by the spider's own weight during repair was reduced.

Toxins from Venomous Arthropods in Brazil: Patents and Potential Biotechnological Applications

Background: The diversity of components in arthropod venoms constitute a rich source of bioactive molecules. Brazil is the most biodiverse country of the world, comprising 15 to 20% of the total catalogued species, with approximately 103,870 animal species including arthropods. Although many articles mention the biotechnological potential of these venoms and toxins, only few studies compile the patented uses of these molecules. Objective: This review describes the knowledge about the molecular mechanism of venoms and toxins with biotechnological potential, and list the patents deposited up to 2021 related to the main medical relevant arthropods in Brazil including the orders Araneae (spider genus Phoneutria, Loxosceles, Latrodectus), Scorpiones (scorpion genus Tityus), Lepidoptera (caterpillar genus Lonomia), and Hymenoptera. Methods: The international patent search engine “Espacenet” and the “Brazilian patent office” were used to search the patents described in this article. Results: Up to date, 34 patents have been filled involving these Brazilian arthropods' venoms or toxins. Most of them (20) claimed biotechnological inventions with spider toxins, mainly from the genus Phoneutria. Only seven inventions involved venom or toxins from scorpions, one from bee, three from wasps, and three from caterpillars. Conclusions: Brazil is one of the main references in venoms and toxins’ studies; however, the limited number of deposited patents related to this area by Brazilian researchers do not reflect their pioneer position in this field. On the other hand, patents were well described and made with purified toxins, rather than with the whole venom. Nevertheless, the vast publication record of venom and toxin characterization that leads to a better understanding of their molecular mechanisms paves the way for turning these promising molecules into possible products.

Population level variation in silk chemistry but not web architecture in a widely distributed orb web spider

Abstract Spider webs are iconic examples of extended phenotypes that are remarkably plastic across different environments. Orb webs are not only effective traps for capturing prey, but can also provide information to potential mates and, in some cases, potential predators and prey through silk-based chemicals. As with regular phenotypic traits, variability in the properties of spider webs is thought to be mediated by a combination of genetic and environmental effects. Here, we examined variation in several key features of the webs of the orb-weaving spider Argiope keyserlingi across five geographically disparate populations. We documented variation in web architecture and chemical properties of webs collected directly from the field. We then probed the potential for the underlying environmental driver of local insect abundance to explain this variation, by analysing the properties of orb webs constructed by the spiders from these different populations, but under identical laboratory conditions. We found no evidence of variation across populations in the architecture of webs constructed in the laboratory, despite the large geographic distances. Nonetheless, we discovered between population variation in the composition of chemicals found on the surface of silk and in the taxonomic distribution of available prey. Furthermore, there was a positive correlation between the quantity of nitrogenous compounds in web silks and female body condition. When combined, these findings suggest that environmental mechanisms can drive variation in web traits across spider populations.

The new Australian leaf-curling orb-weaving spider genus Leviana (Araneae, Araneidae)

The new Australian orb-weaving spider genus Levianagen. nov. is described to include five species, all known from both sexes: Leviana dimidiata (L. Koch, 1871) comb. nov. (type species) (= Epeira sylvicola Rainbow, 1897 syn. nov.), L. cincinnatasp. nov., L. foliumsp. nov., L. minimasp. nov. and L. mulieraria (Keyserling, 1887) comb. nov. Male pedipalp morphology, specifically the presence of a single patella spine and the median apophysis forming an arch over the radix, place Levianagen. nov. in the informal Australian ‘backobourkiine’ clade; however, the genus differs from all other genera of this group by the presence of a spine inside the basal median apophysis arch of the male pedipalp, an epigyne that is wider than long with a scape that is approximately as long as the epigyne (but often broken off) and a lack of humeral humps on the elongate ovoid abdomen. In addition, unlike any other backobourkiine, Levianagen. nov. incorporate a rolled leaf as retreat into the periphery of their web. Levianagen. nov. species exhibit only a moderate sexual size dimorphism with female to male ratios between 1.3 and 1.7. Levianagen. nov. occurs in eastern Australia from northern Queensland in the north to Victoria in the south, with a single tropical species, L. mulierariacomb. nov., spreading into northern Western Australia.

RECORDS OF PREDATORS AND PARASITES (VERTEBRATES AND INVERTEBRATES) OF CREOSOTE BUSH GRASSHOPPER BOOTETTIX ARGENTATUS BRUNER, 1889, (ORTHOPTERA: ACRIDIDAE: GOMPHOCERINAE) FROM THE BOLSÓN DE MAPIMI, DGO. (CHIHUAHUAN DESERT), MEXICO

This paper summarizes unpublished information and isolated field observation records on the principal predators (9 vertebrates, 10 insect and 2 orb weaver and a terrestrial spider species) and parasites (an insect and one mite species) of B. argentatus a non economic, highly specialized monophagous grasshopper species of creosote bushes Larrea tridentata in Mapimi Biosphere Reserve, a southern region of the Chihuahuan Desert.

What is adaptive radiation? Many manifestations of the phenomenon in an iconic lineage of Hawaiian spiders

Adaptive radiation provides the ideal context for identifying and testing the processes that drive evolutionary diversification. However, different adaptive radiations show a variety of different patterns, making it difficult to come up with universal rules that characterize all such systems. Diversification may occur via several mechanisms including non-adaptive divergence, adaptation to novel environments, or character displacement driven by competition. Here, we characterize the ways these different drivers contribute to present-day diversity patterns, using the exemplary adaptive radiation of Hawaiian long-jawed orbweaver (Tetragnatha) spiders. We present the most taxonomically comprehensive phylogenetic hypothesis to date for this group, using 10 molecular markers and representatives from every known species across the archipelago. Among the lineages that make up this remarkable radiation, we find evidence for multiple diversification modalities. Several clades appear to have diversified in allopatry under a narrow range of ecological conditions, highlighting the role of niche conservatism in speciation. Others have shifted into new environments and evolved traits that appear to be adaptive in those environments. Still others show evidence for character displacement by close relatives, often resulting in convergent evolution of stereotyped ecomorphs. All of the above mechanisms seem to have played a role in giving rise to the exceptional diversity of morphological, ecological and behavioral traits represented among the many species of Hawaiian Tetragnatha. Taking all these processes into account, and testing how they operate in different systems, may allow us to identify universal principles underlying adaptive radiation.

Spider Launch: Male orb weavers spring away to survive mating.

Spider Launch: Male orb weavers spring away to survive mating.

Two New Species of Orb-Weaving Spiders of the Genera Cyrtarachne Thorell, 1868 and Pasilobus Simon, 1895 (Araneae: Araneidae) from India

Two new species of orb-weaving spiders, Cyrtarachne wayanadensis sp. nov. and Pasilobus sahyadriensis sp. nov., are recorded from Southern Western Ghats, Kerala. Detailed description and illustrations of the new species are provided.

CHECKLIST OF SPIDERS (ARACHNIDA ARANEAE) FROM CHAMPANER PAVAGADH ARCHAEOLOGICAL PARK, GUJARAT

Spiders are one of the most diverse organisms in the terrestrial ecosystem and occupy the seventh position in global diversity. They are arthropods belonging to the class Arachnida and the order Araneae. Spiders are chiefly entomophagous, ubiquitous, harmless and biocontrol agents. The present study was conducted to document spider diversity in Champaner- Pavagadh Archaeological Park; a world heritage site in Gujarat, India. The spider fauna of this site has never been studied in its entirety despite contributions by many arachnologists in Gujarat. Spiders were collected by using active searching, pitfall, and sweep net methods. The study was conducted from January 2016 to December 2019. In the present research work, we compiled a checklist of spiders from Champaner-Pavagadh, Archaeological Park of Gujarat, India based on their taxonomic identification. A total of 189 species belonging to 106 genera and 32 families were collected during the study. The most dominant families reported were Salticidae followed by Araneidae, Lycosidae, and Theridiidae; Oxyopidae and Thomisidae. Finding twenty-seven new records of spiders is the highlight of this work

QS50. Elucidating the Reasons Behind the Success of Spider Silk In Nerve Regeneration

Purpose: The successful reconstruction of peripheral nerve injuries remains a major clinical challenge. Nerve guidance conduits are a promising alternative to autologous nerve transplantation and conduits filled with fibrous materials have shown great potential in bridging nerve gaps. The application of spider silk as a filament material for nerve guidance conduits has led to results comparable to nerve autograft. However, the use of spider silk has been phenomenological so far and the reasons for its success are still not identified. The aim of this study is to elucidate the material properties of spider silk leading to its unique medical performance. This knowledge enables a targeted production of synthetic alternatives such as recombinant silk. Methods: In this work, various silk types from golden orb weavers and tarantulas were investigated. In vitro experiments were conducted, and Schwann cells were seeded on the spider silks and monitored by live cell imaging. The extent of proliferation was analyzed by immunofluorescent staining and confocal microscopy. In addition, the silk fibers were inspected with an electron microscope for differences in their morphology and with Raman spectroscopy as well as wide angle X-ray scattering to determine their secondary protein structure and crystallinity. Results: It was found that the adhesion of Schwann cells on spider silk is independent of the size and morphology of fibers. However, the secondary protein structure and specifically the high content of β-sheets in the direction of silk’s axis gives the fiber its ability to act as a guiding element for Schwann cells. In addition, the results show that the crystallinity of the silk does not affect the proliferation of Schwann cells, while the directed movement of cells is affected by this material property. Conclusion: This direct comparison demonstrated the crucial role of the secondary protein structures and crystallinity of spider silk for the guidance properties of fibers during nerve regeneration. These results should be considered during the targeted production of synthetic fibrous materials for nerve regeneration.

Characterization of the genome and silk-gland transcriptomes of Darwin's bark spider (Caerostris darwini).

Natural silks crafted by spiders comprise some of the most versatile materials known. Artificial silks-based on the sequences of their natural brethren-replicate some desirable biophysical properties and are increasingly utilized in commercial and medical applications today. To characterize the repertoire of protein sequences giving silks their biophysical properties and to determine the set of expressed genes across each unique silk gland contributing to the formation of natural silks, we report here draft genomic and transcriptomic assemblies of Darwin's bark spider, Caerostris darwini, an orb-weaving spider whose dragline is one of the toughest known biomaterials on Earth. We identify at least 31 putative spidroin genes, with expansion of multiple spidroin gene classes relative to the golden orb-weaver, Trichonephila clavipes. We observed substantial sharing of spidroin repetitive sequence motifs between species as well as new motifs unique to C. darwini. Comparative gene expression analyses across six silk gland isolates in females plus a composite isolate of all silk glands in males demonstrated gland and sex-specific expression of spidroins, facilitating putative assignment of novel spidroin genes to classes. Broad expression of spidroins across silk gland types suggests that silks emanating from a given gland represent composite materials to a greater extent than previously appreciated. We hypothesize that the extraordinary toughness of C. darwini major ampullate dragline silk may relate to the unique protein composition of major ampullate spidroins, combined with the relatively high expression of stretchy flagelliform spidroins whose union into a single fiber may be aided by novel motifs and cassettes that act as molecule-binding helices. Our assemblies extend the catalog of sequences and sets of expressed genes that confer the unique biophysical properties observed in natural silks.

Male mating strategies to counter sexual conflict in spiders

When sexual conflict selects for reproductive strategies that only benefit one of the sexes, evolutionary arms races may ensue. Female sexual cannibalism is an extreme manifestation of sexual conflict. Here we test two male mating strategies aiming at countering sexual cannibalism in spiders. The “better charged palp” hypothesis predicts male selected use of the paired sexual organ (palp) containing more sperm for their first copulation. The “fast sperm transfer” hypothesis predicts accelerated insemination when cannibalism is high. Our comparative tests on five orbweb spider species with varying levels of female sexual cannibalism and sexual size dimorphism (SSD) reveal that males choose the palp with more sperm for the first copulation with cannibalistic females and that males transfer significantly more sperm if females are cannibalistic or when SSD is biased. By supporting the two hypotheses, these results provide credibility for male mating syndrome. They, however, open new questions, namely, how does a male differentiate sperm quantities between his palps? How does he perform palp choice after assessing his cannibalistic partner? By conducting follow-up experiments on Nephilengys malabarensis, we reveal that it is sperm volume detection, rather than left-right palp dominance, that plays prominently in male palp choice.

Correlated evolution between orb weaver glue droplets and supporting fibres maintains their distinct biomechanical roles inadhesion.

Orb weaving spiders employ a ‘silken toolkit’ to accomplish a range of tasks, including retaining prey that strike their webs. This is accomplished by a viscous capture spiral thread that features tiny glue droplets, supported by a pair of elastic flagelliform fibres. Each droplet contains a glycoprotein core responsible for adhesion. However, prey retention relies on the integrated performance of multiple glue droplets and their supporting fibres, with previous studies demonstrating that a suspension bridge forms, whose biomechanics sum the adhesive forces of multiple droplets while dissipating the energy of the struggling insect. While the interdependence of the droplet's glycoprotein and flagelliform fibres for functional adhesion is acknowledged, there has been no direct test of this hypothesized linkage between the material properties of each component. Spider mass, which differs greatly across orb weaving species, also has the potential to affect flagelliform fibre and glycoprotein material properties. Previous studies have linked spider mass to capture thread performance but have not examined the relationship between spider mass and thread material properties. We extend earlier studies to examine these relationships in 16 orb weaving species using phylogenetic generalized least squares. This analysis revealed that glycoprotein stiffness (elastic modulus) was correlated with flagelliform fibre stiffness, and that spider mass was related to the glycoprotein volume, flagelliform fibre cross‐sectional area and droplets per unit thread length. By shaping the elastic moduli of glycoprotein adhesive and flagelliform fibres, natural selection has maintained the biomechanical integration of this adhesive system.

Characterization of two full-length Araneus ventricosus major ampullate silk protein genes

Major ampullate silk is noted for its great tensile strength and extensibility. The impressive material properties of major ampullate silk result from their component proteins that encoded by members of the spidroin (spider fibroin) gene family. Although the major ampullate spidroin type has evolved multiple variants within specific-species, most sequences are fragmented. Here, we present two complete major ampullate spidroin genes from the orb-weaving spider Araneus ventricosus. Due to the abundant GPG motifs in their repetitive region, the two MaSp genes were grouped in MaSp2 subclass and named MaSp2C and MaSp2D, respectively. Analysis of the full-length gene sequences reveals that both of them include a single enormous exon (10,851 bp for MaSp2C and 8640 bp for MaSp2D) that mainly translates into a central repetitive region containing multiple amino acid motifs that can be organized into five ensemble types. We use gene-specific PCR primers to search the cDNA from major ampullate glands and find evidence for alternative splicing of MaSp2D transcripts into a minor spliceoform lacking the entire repetitive domain as well as the partial terminal regions. Our results not only provide new templates for protein-based materials with tailored properties, but suggest gene and transcriptional diversity of major ampullate silk.