Large Spiders Research Articles

A strategy for sensing the petal mode in the presence of AO residual turbulence with the pyramid wavefront sensor

Context. With the Extremely Large Telescope (ELT) generation of telescopes come new challenges. The complexity of these telescopes’ pupils creates new problems for adaptive optics (AO) that prevent the telescopes from reaching the theoretical resolutions that their size allows. In particular, the large spiders necessary to support the massive optics of these telescopes create discontinuities in the wavefront measurement. These discontinuities appear as a new phase error dubbed the “petal mode.” This error is described as a differential piston between the fragment of the pupil separated by the spiders and is responsible for a strong degradation in the imaging quality, reducing the European ELT’s resolution to that of a 15m telescope. Aims. The aim of this paper is to study the measurement of the petal mode by AO sensors. In particular, we want to understand why the pyramid wavefront sensor (PyWFS), the first-light wavefront sensor of any ELT-generation telescope, cannot measure this petal mode under normal conditions, and how to enable this measurement by adapting the AO control scheme and the PyWFS. Methods. To facilitate our study, we considered a simplified version of the petal mode, featuring a simpler pupil than the ELT. This allowed us to quickly simulate the properties of the petal mode and its measurement by the PyWFS. We studied specifically how a system that separates the atmospheric turbulence from the petal measurement would behave. Studying the petal mode’s power spectral density, we proposed using a spatial filter to reduce the contribution of AO residuals to the benefit of petal mode contribution, eventually enabling it to be measured. Finally, we demonstrated our proposed system with end-to-end simulations. Results. A solution proposed to measure the petal mode is to use an unmodulated PyWFS (uPyWFS), but the uPyWFS does not make accurate measurements in the presence of atmospheric residuals. A spatial filtering step, consisting of a pinhole around the pyramid tip, reduces the first path residuals seen by the uPyWFS and restores its accuracy. This system was able to measure and control the petal mode during the end-to-end simulation. Conclusions. To address the petal problem, a two-path AO with a sensor dedicated to the measurement of the petal mode seems necessary. The question remains as to what could be used as the second path petalometer. Through this paper, we demonstrate that an uPyWFS can confuse the petal mode with the residuals from the first path. However, adding a spatial filter on top of said uPyWFS makes it a good petalometer candidate. This spatial filtering step makes the uPyWFS less sensitive to the first path residuals while retaining its ability to measure the petal mode.

First data on the spider fauna (Arachnida: Aranei) of the Salair National Park and surroundings (Altaisky Krai, Russia)

For the fi rst time, the spider fauna of the Salair National Park and adjacent territories is studied in detail and its zoogeographical characteristics are given. The surveys were carried out in the Togul and Chumysh cluster areas and adjacent territories in 2020–2022. An annotated list has been compiled, including 118 species from 17 families and 77 genera. Twenty seven species of spiders were recorded in the Altai Territory for the fi rst time. The genus Enoplognatha Pavesi, 1880 is new to the region. The family Linyphiidae is the most diverse. At the generic level, small- sized wolf spiders of the genus Pardosa C. L. Koch, 1847 and large orb-web spiders of the genus Araneus Clerck, 1757 are represented by the highest number of species (6 and 5, respectively). The analysis of longitudinal components of the ranges of the collected species showed a signifi cant predominance (more than 70%) of widespread, trans- Palaearctic and trans- Holarctic elements. Twenty percent of species are common to the fauna of Europe and Siberia. The predicted spider species diversity of this region is 300–350 species.

Miniaturization does not change conserved spider anatomy, a case study on spider Rayforstia (Araneae: Anapidae)

Miniaturization is an evolutionary trend observed in many animals. Some arachnid groups, such as spiders and mites, demonstrate a strong tendency toward miniaturization. Some of the most miniaturized spiders belong to the family Anapidae. In this study, using light and confocal microscopy and 3D modelling, we provide the first detailed description of the anatomy of a spider of the genus Rayforstia, which is only 900 µm long. In comparison with larger spiders, Rayforstia has no branching of the midgut in the prosoma and an increased relative brain volume. In contrast to many miniature insects and mites, the spider shows no reduction of whole organ systems, no allometry of the digestive and reproductive systems, and also no reduction of the set of muscles. Thus, miniature spider shows a more conserved anatomy than insects of a similar size. These findings expand our knowledge of miniaturization in terrestrial arthropods.

A large brush-footed trapdoor spider (Mygalomorphae: Barychelidae) from the Miocene of Australia

Abstract The aridification of the Australian continent led to the diversification of mygalomorph spiders in the Miocene, but a depauperate fossil record has made it difficult to investigate evolution across this epoch. Here, we describe the first fossil barychelid spider (Araneae: Barychelidae) in the world and the second fossil mygalomorph spider from Australia. It is placed as a new genus and species (Megamonodontium mccluskyi gen. et sp. nov.). Megamonodontium resembles Monodontium Kulczyński, 1908, a genus that persists in rainforests through Singapore, Indonesia and Papua New Guinea. The new specimen is the second largest spider fossil in the world and is approximately five times larger than extant Monodontium. The fossil shows that this lineage once occupied mesic rainforest habitats in Australia but has since been replaced by other spiders.

A survey of Tmarus Simon, 1875 (Araneae, Thomisidae) from Fanjing Mountain Nature Reserve, Guizhou, China.

Tmarus Simon, 1875 is a relatively large spider genus, currently includes 227 species distributed worldwide. Fanjing Mountain Nature Reserve is one of China's most biodiverse regions. However, Tmarus can be regarded as being poorly represented in Fanjing Mountain, with only one species having been recorded so far: T.fanjing Yang & Yu, 2022. Recently, various expeditions to Fanjing Mountain Nature Reserve were carried out by the authors. In this paper, two Tmarus species were brought to light by those expeditions: T.fanjing Yang & Yu, 2022 and T.circinalis Song & Chai, 1990. T.fanjing is redescribed, based on new material and the female is described and illustrated for the first time. The supplementary micrographs of T.circinalis are given for the first time. The DNA barcodes and a distribution map of both species are provided for future use.

Factors influencing predation on Odonata by Argiope trifasciata (Forsskål, 1775)

Despite a high number of incidental online records of spiders predating upon dragonflies/damselflies, studies on these interactions are scarce. Here, we describe the predatory behavior of Argiope trifasciata on the two most common odonate species in the study area, and whether various factors (web width, web length, spider body length, odonate body length, distance of the web from the edge of water body, and height of the web above ground) are related to the number of odonates captured. Argiope trifasciata employed stalking and frontal approaches as Odonata predation strategies. Our findings showed that larger Odonata are preyed upon by larger spiders. The greatest numbers of prey were caught in wider, higher webs, whereas narrow webs closer to the ground caught more small prey. Capturing success by A. trifasciata was similar in webs at different distances from the water for both species. Contrary to our hypothesis, there was no relationship between capturing success in either prey species and the distance of the web from the water. Habitat architecture may be more important to this interaction, as vegetation attracts both spiders (for anchoring webs) and odonates (as perch sites).

Effect of forest fires on a Mediterranean Odonata assemblage

Despite a high number of incidental online records of spiders predating upon dragonflies/damselflies, studies on these interactions are scarce. Here, we describe the predatory behavior of Argiope trifasciata on the two most common odonate species in the study area, and whether various factors (web width, web length, spider body length, odonate body length, distance of the web from the edge of water body, and height of the web above ground) are related to the number of odonates captured. Argiope trifasciata employed stalking and frontal approaches as Odonata predation strategies. Our findings showed that larger Odonata are preyed upon by larger spiders. The greatest numbers of prey were caught in wider, higher webs, whereas narrow webs closer to the ground caught more small prey. Capturing success by A. trifasciata was similar in webs at different distances from the water for both species. Contrary to our hypothesis, there was no relationship between capturing success in either prey species and the distance of the web from the water. Habitat architecture may be more important to this interaction, as vegetation attracts both spiders (for anchoring webs) and odonates (as perch sites).

Spiders - It’s not the Way we Think

Spiders, eight legged arthropod for many looks creepy or a yekk creature. When we think of spiders, for majority long & thin legged cellar spiders in corner of our room with messy web comes to mind. For some large huntsman spider with large legs in bathrooms & few with little garden may think of web weaving spiders, which have disturbed them for morning walk.

Island hoppers: Integrative taxonomic revision of Hogna wolf spiders (Araneae, Lycosidae) endemic to the Madeira islands with description of a new species.

Because of their ability for aerial dispersal using silk and preference for open habitats, many wolf spiders are formidable colonisers. Pioneering arachnologists were already aware of the large and colourful wolf spiders in the Madeira archipelago, currently included in the genus Hogna Simon, 1885. The origins were investigated and species boundaries of Madeiran Hogna examined by integrating target-gene and morphological information. A multi-locus phylogenetic analysis of a thorough sampling across wolf-spider diversity suggested a single origin of Madeiran endemics, albeit with low support. Divergence time estimation traced back their origin to the late Miocene, a time of major global cooling that drove the expansion of grasslands and the associated fauna. Morphological examination of types and newly collected material revealed a new species, hereby described as H.isambertoi Crespo, sp. nov. Additionally, H.blackwalli is revalidated and three new synonymies are proposed, namely H.biscoitoi Wunderlich, 1992, junior synonym of H.insularum Kulczynski, 1899, H.schmitzi Wunderlich, 1992, junior synonym of H.maderiana (Walckenaer, 1837), and Arctosamaderana Roewer, 1960 junior synonym of H.ferox (Lucas, 1838). Species delimitation analyses of mitochondrial and nuclear markers provided additional support for morphological delineations. The species pair H.insularum and H.maderiana, however, constituted an exception: the lack of exclusive haplotypes in the examined markers, along with the discovery of intermediate forms, pointed to hybridisation between these two species as reported in other congeneric species on islands. Finally, the conservation status of the species is discussed and candidates for immediate conservation efforts are identified.

From crypsis to masquerade: Ontogeny changes the colour defences of a crab spider hiding as bird droppings

Abstract Selection imposed by visually hunting predators has driven the evolution of colour‐based antipredator defence strategies such as crypsis, masquerade, mimicry and aposematism. Individuals of many animals are generally considered to rely on a single type of defence strategy, but individuals of some species use multiple colour‐based defences. Many animals switch between colour‐based defences against visually hunting predators during ontogeny. However, why this occurs remains poorly understood. The crab spider Phrynarachne ceylonica is an often‐cited example of a bird dropping masquerade. It has recently been demonstrated that P. ceylonica crab spiders gain protection from their predators by being misidentified as bird droppings by their predators. P. ceylonica females show an ontogenetic shift in colour defences: early instars possess a dark and cryptic form, while at later instars and as adults, the spiders resemble bird droppings. We hypothesised that this shift may be driven by differential changes in predation risk of two defence strategies with increasing body size due to ontogeny. We tested this hypothesis by presenting naïve domestic chicks with 3D printed artificial spiders of two different sizes (small, large) and two colours (dark, bird dropping‐like), and determined whether larger bird dropping‐like spiders are more readily found and attacked than cryptic forms by chicks. We found that small cryptic spiders were more difficult to detect than small bird dropping masquerading spiders, but large cryptic spiders were attacked much more quickly and more frequently than large bird dropping masquerading spiders. Increasing predation pressure on larger, cryptic spiders during ontogeny suggests that switching to bird dropping masquerade may be a more effective defence as spiders increase in size. We thus conclude that the ontogenetic shift from crypsis to masquerade is adaptive.

On the Dangers of Tropical Spiders as a Pet: A Review of Ocular Symptoms Caused by Tarantula Hairs.

Tarantulas are large spiders that can defend themselves by shedding urticating hairs (setae). In this paper, we aim to discuss the ocular conditions caused by these setae through a literature review. In total, 25 cases were identified in the PubMed database. Tarantula setae have a barbed structure that enables migration through the globe. They give rise to a spectrum of complaints, causing a granulomatous inflammatory reaction in the compartment they settle. Superficial corneal hairs cause a mild keratitis, while hairs that penetrate Descemet's membrane can induce an anterior uveitis. Both can be treated with local steroids; when possible, hairs should be debrided. Setae that migrate into the posterior segment can cause a focal vitritis that can be more difficult to treat, sometimes requiring vitrectomy.

Economies of scale shape energetics of solitary and group-living spiders and their webs.

Metabolic scaling, whereby larger individuals use less energy per unit mass than smaller ones, may apply to the combined metabolic rate of group-living organisms as group size increases. Spiders that form groups in high disturbance environments can serve to test the hypothesis that economies of scale benefit social groups. Using solitary and group-living spiders, we tested the hypothesis that spiders exhibit negative allometry between body or colony mass and the standing mass of their webs and whether, and how, such a relationship may contribute to group-living benefits in a cooperative spider. Given the diverse architecture of spider webs-orb, tangle and sheet-and-tangle, and associated differences in silk content, we first assessed how standing web mass scales with spider mass as a function of web architecture and whether investment in silk differs among web types. As group-living spiders are predominantly found in clades that build the presumably costlier sheet-and-tangle webs, we then asked whether cost-sharing through cooperative web maintenance contributes to a positive energy budget in a social species. We found that larger spiders had a relatively smaller investment in silk per unit mass than smaller ones, but more complex sheet-and-tangle webs contained orders of magnitude more silk than simpler orb or tangle ones. In the group-living species, standing web mass per unit spider mass continued to decline as colony size increased with a similar slope as for unitary spiders. When web maintenance activities were considered, colonies also experienced reduced mass-specific energy expenditure with increasing colony size. Activity savings contributed to a net positive energy balance for medium and large colonies after inputs from the cooperative capture of large prey were accounted for. Economies of scale have been previously demonstrated in animal societies characterized by reproductive and worker castes, but not in relatively egalitarian societies as those of social spiders. Our findings illustrate the universality of scaling laws and how economies of scale may transcend hunting strategies and levels of organization.

Prey–predator interactions and body size relationships between annual cicadas and spiders in Japan

ABSTRACT Cicada (Hemiptera) emergence is a major resource pulse that produces diverse effects on terrestrial food webs. Most studies have focused on periodical cicadas; however, little is known regarding the prey–predator interactions and size relationships between annual cicadas and predators, with knowledge being exclusively limited to the cicada–bird systems. Here, we focused on the interactions between annual cicadas and spiders in Japan. Based on direct observations and posts on social networking services and blogs on the Internet, we aimed to (1) reveal the major spider taxa as the predators of annual cicadas, (2) identify the major cicada taxa as the prey of spiders, and (3) characterise the prey–predator body size relationships between annual cicadas and spiders. Large orb-web spiders of the family Araneidae were identified as the major predators of annual cicadas. Spiders preyed on diverse cicada species, and prey species composition varied among the predator species. Regarding body size ratio, spiders tended to prey on cicadas larger than themselves (prey–predator body size ratio >1). We suggest that orb-weavers may function as one of the key predators of annual cicadas. Annual and periodical cicadas may be preyed upon by predators that use different foraging modes (web-builders or cursorial hunters). Further examination of these prey–predator interactions will contribute to the understanding of the cicada–predator systems.

Shaped by the Sun: the effect of exposure to sunlight on the evolution of spider bodies.

Body temperature can strongly influence fitness. Some Sun-exposed ectotherms thermoregulate by adjusting body posture according to the Sun's position. In these species, body elongation should reduce the risk of heat stress by allowing the exposure of a smaller body area to sunlight. Therefore, selection should favour more elongated bodies in Sun-exposed than in Sun-protected species. Diurnal orb-web spider species that sit on their webs are more likely to be Sun-exposed, on average, than nocturnal or diurnal shelter-building species. We measured the body elongation of orb-web spiders (Araneae, Araneidae) across 1024 species and classified them as Sun-protected or exposed based on the literature. We found that Sun-exposed species evolved more elongate bodies than Sun-protected ones. Further, we built a model combining traditional heat transfer models with models of thermoregulatory postures in orb-web spiders and meteorological data. The model indicates that body elongation in large orb-web spiders decreases the risk of high body temperatures. Overall, our results suggest that Sun exposure influenced the evolution of body shapes of orb-web spiders.

Large spiders don't stop under pressure

Large spiders don't stop under pressure

Complete mitochondrial genomes and phylogenetic relationships of the genera Nephila and Trichonephila (Araneae, Araneoidea)

Spiders of the genera Nephila and Trichonephila are large orb-weaving spiders. In view of the lack of study on the mitogenome of these genera, and the conflicting systematic status, we sequenced (by next generation sequencing) and annotated the complete mitogenomes of N. pilipes, T. antipodiana and T. vitiana (previously N. vitiana) to determine their features and phylogenetic relationship. Most of the tRNAs have aberrant clover-leaf secondary structure. Based on 13 protein-coding genes (PCGs) and 15 mitochondrial genes (13 PCGs and two rRNA genes), Nephila and Trichonephila form a clade distinctly separated from the other araneid subfamilies/genera. T. antipodiana forms a lineage with T. vitiana in the subclade containing also T. clavata, while N. pilipes forms a sister clade to Trichonephila. The taxon vitiana is therefore a member of the genus Trichonephila and not Nephila as currently recognized. Studies on the mitogenomes of other Nephila and Trichonephila species and related taxa are needed to provide a potentially more robust phylogeny and systematics.

Body size and tree species composition determine variation in prey consumption in a forest-inhabiting generalist predator.

Trophic interactions may strongly depend on body size and environmental variation, but this prediction has been seldom tested in nature. Many spiders are generalist predators that use webs to intercept flying prey. The size and mesh of orb webs increases with spider size, allowing a more efficient predation on larger prey. We studied to this extent the orb‐weaving spider Araneus diadematus inhabiting forest fragments differing in edge distance, tree diversity, and tree species. These environmental variables are known to correlate with insect composition, richness, and abundance. We anticipated these forest characteristics to be a principle driver of prey consumption. We additionally hypothesized them to impact spider size at maturity and expect shifts toward larger prey size distributions in larger individuals independently from the environmental context. We quantified spider diet by means of metabarcoding of nearly 1,000 A. diadematus from a total of 53 forest plots. This approach allowed a massive screening of consumption dynamics in nature, though at the cost of identifying the exact prey identity, as well as their abundance and putative intraspecific variation. Our study confirmed A. diadematus as a generalist predator, with more than 300 prey ZOTUs detected in total. At the individual level, we found large spiders to consume fewer different species, but adding larger species to their diet. Tree species composition affected both prey species richness and size in the spider's diet, although tree diversity per se had no influence on the consumed prey. Edges had an indirect effect on the spider diet as spiders closer to the forest edge were larger and therefore consumed larger prey. We conclude that both intraspecific size variation and tree species composition shape the consumed prey of this generalist predator.

Size-related increase in inducible mechanical variability of major ampullate silk in a huntsman spider (Araneae: Sparassidae).

Most spiders use major ampullate silk (MAS) to perform many functions across their lifetimes, including prey capture, vibratory signal detection, and safety/dragline. To accommodate their various needs, adult spiders can use inducible variability to tailor MAS with specific mechanical properties. However, it is currently unknown whether this inducible mechanical variability develops gradually or remains consistent across spider size. Supercontraction -a process by which "native-state" silk fibers axially shrink when exposed to water or high humidity-can be used to reveal the extent of inducible variability in MAS. Supercontraction removes some processing effects that occur during the spinning of the solid fiber from its liquid precursor by allowing a native-state MAS fiber to return to a low energy "ground-state". Here, we examined the relative extent of inducible variability of MAS across spider size by assessing supercontraction properties and the difference between ground- and native-state MAS tensile properties using silk from the huntsman spider Heteropoda venatoria (Sparassidae). Stiffness of forcibly pulled native-state silk increased by 200% with spider size. After exposure to 90% RH and subsequent supercontraction, axial shrinkage of native-state silk fibers increased by 15% in larger spiders. Supercontracted, ground-state fibers demonstrated a 200% increase in extensibility across spider size. Our results indicate a gradual increase in inducible variability of MAS mechanical properties across spider size potentially caused by shifts in internal processing or chemical composition. These findings imply both development of inducible variability and changes in use of MAS as a safety line or aiding jumps across a spider's lifetime.

The sublethal effects of neonicotinoids on spiders are independent of their nutritional status

Spiders were recently shown to be adversely affected by field-realistic concentrations of a broad scale of neonicotinoid insecticides. Among the reported effects of neonicotinoids on invertebrates were declines in lipid biosynthesis and upregulation of β-oxidation, while vertebrate models suggest increased adipogenesis following treatment with neonicotinoids. Therefore, we hypothesized that there exists synergy between the effects of diet and concurrent exposure to field-realistic concentrations of neonicotinoid insecticides. To address this hypothesis, we fed first instars of the large wolf spider Hogna antelucana with two types of diets and exposed them to field-realistic concentrations of three formulations of neonicotinoids (thiamethoxam, thiacloprid and acetamiprid). We then measured the growth of the tested spiders; the lipid and protein content of their bodies; and their behavior, including ballooning, rappelling, and locomotor parameters. The two tested diets consisted of casein-treated and sucrose-treated Drosophila melanogaster. The dietary treatments affected the lipid and protein content of the spiders, their body weight and carapace length but did not affect any of the measured behavioral parameters. Surprisingly, we did not find any effects of acute exposure to neonicotinoid insecticides on the lipid or protein reserves of spiders. Exposure to neonicotinoids altered the behavior of the spiders as reported previously in other spider species; however, these effects were not affected by dietary treatments. Overall, the dietary treatments did not have any major synergy with acute exposure to field-realistic concentrations of neonicotinoid insecticides.

Co-extracted electrons and beam inhomogeneity in the large negative ion source SPIDER

The SPIDER ion source has been designed to generate a current of H- ions up to 60 A and accelerate them up to 100 keV. In addition, the ratio between the co-extracted electrons and negative ions has to be below 1, and a beam inhomogeneity within 10 % has to be attained.A magnetic filter field is produced by a current flowing through the plasma electrode in the vertical direction with the aim of reducing electron temperature and density in the extraction region, so as to enhance the survival probability of H- ions while reducing the co-extracted electrons. Another strategy to reduce the co-extracted electrons is to apply a small bias voltage to the plasma grid with respect to the ion source body. In addition to this, a so-called bias plate is installed in the vicinity of the plasma grid, which can also be biased with respect to source body. However, the application of a bias voltage affects the beam inhomogeneity by modifying the ExB plasma drift within the ion source. Recently, the filter field configuration of SPIDER was modified so as to improve the plasma diffusion towards the extraction region. In addition, the voltage ratings of the bias power supplies were increased. Both these modifications permit to efficiently lower the electron co-extracted current. The present contribution describes such improvements while focusing on the effects they have on the beam inhomogeneity.