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Foll, Didier Le, Evelyne Brichet, Jean Louis Reyss, Claude Lalou et Daniel Latrouite. « Age Determination of the Spider Crab Maja squinado and the European Lobster Homarus gammarus by 228Th/228Ra Chronology : Possible Extension to Other Crustaceans ». Canadian Journal of Fisheries and Aquatic Sciences 46, no 4 (1 avril 1989) : 720–24. http://dx.doi.org/10.1139/f89-091.
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A method of age determination was developed on carapaces of the spider crab, Maja squinado Herbst and European lobster Homarus gammarus L., by measuring the natural radionuclides activity ratio, 228Th/228Ra in the exoskeleton. This method allows the determination of the time elapsed since the preceding molt of the animal. It was successfully tested on five spider crabs and four lobsters which had molted in captivity and therefore had a carapace of known age. It is probable that the method could, with some reservations, be extended to all marine Decapod Crustacea bearing a well calcified exoskeleton.
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Kariko, Sarah, Jaakko V. I. Timonen, James C. Weaver, Dvir Gur, Carolyn Marks, Leslie Leiserowitz, Mathias Kolle et Ling Li. « Structural origins of coloration in the spider Phoroncidia rubroargentea Berland, 1913 (Araneae : Theridiidae) from Madagascar ». Journal of The Royal Society Interface 15, no 139 (février 2018) : 20170930. http://dx.doi.org/10.1098/rsif.2017.0930.
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This study investigates the structural basis for the red, silver and black coloration of the theridiid spider, Phoroncidia rubroargentea (Berland, 1913) from Madagascar. Specimens of this species can retain their colour after storage in ethanol for decades, whereas most other brightly pigmented spider specimens fade under identical preservation conditions. Using correlative optical, structural and chemical analysis, we identify the colour-generating structural elements and characterize their optical properties. The prominent silvery appearance of the spider's abdomen results from regularly arranged guanine microplatelets, similar to those found in other spiders and fish. The microplatelets are composed of a doublet structure twinned about the [ ] axis, as suggested by electron diffraction. The red coloration originates from chambered microspheres (approx. 1 µm in diameter), which contain structured fluorescent material. Co-localization of the red microparticles on top of the reflective guanine microplatelets appears to enhance the red coloration. The spider's thick cuticular layer, which encases its abdomen, varies in its optical properties, being transparent in regions where only guanine reflectors are present, and tanned, exhibiting light absorption where the red microspheres are found. Moreover, colour degradation in some preserved spider specimens that had suffered damage to the cuticular layer suggests that this region of the exoskeleton may play an important role in the stabilization of the red coloration.
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Schaber, Clemens F., Stanislav N. Gorb et Friedrich G. Barth. « Force transformation in spider strain sensors : white light interferometry ». Journal of The Royal Society Interface 9, no 71 (26 octobre 2011) : 1254–64. http://dx.doi.org/10.1098/rsif.2011.0565.
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Scanning white light interferometry and micro-force measurements were applied to analyse stimulus transformation in strain sensors in the spider exoskeleton. Two compound or ‘lyriform’ organs consisting of arrays of closely neighbouring, roughly parallel sensory slits of different lengths were examined. Forces applied to the exoskeleton entail strains in the cuticle, which compress and thereby stimulate the individual slits of the lyriform organs. (i) For the proprioreceptive lyriform organ HS-8 close to the distal joint of the tibia, the compression of the slits at the sensory threshold was as small as 1.4 nm and hardly more than 30 nm, depending on the slit in the array. The corresponding stimulus forces were as small as 0.01 mN. The linearity of the loading curve seems reasonable considering the sensor's relatively narrow biological intensity range of operation. The slits' mechanical sensitivity (slit compression/force) ranged from 106 down to 13 nm mN −1 , and gradually decreased with decreasing slit length. (ii) Remarkably, in the vibration-sensitive lyriform organ HS-10 on the metatarsus, the loading curve was exponential. The organ is thus adapted to the detection of a wide range of vibration amplitudes, as they are found under natural conditions. The mechanical sensitivities of the two slits examined in this organ in detail differed roughly threefold (522 and 195 nm mN −1 ) in the biologically most relevant range, again reflecting stimulus range fractionation among the slits composing the array.
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Gibbons, Alastair T., Alexander Idnurm, Michael Seiter, Paul S. Dyer, Matthew Kokolski, Sara L. Goodacre, Stanislav N. Gorb et Jonas O. Wolff. « Amblypygid-fungal interactions : The whip spider exoskeleton as a substrate for fungal growth ». Fungal Biology 123, no 7 (juillet 2019) : 497–506. http://dx.doi.org/10.1016/j.funbio.2019.05.003.
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Panek, Izabela, Shannon Meisner et Päivi H. Torkkeli. « Distribution and Function of GABAB Receptors in Spider Peripheral Mechanosensilla ». Journal of Neurophysiology 90, no 4 (octobre 2003) : 2571–80. http://dx.doi.org/10.1152/jn.00321.2003.
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The mechanosensilla in spider exoskeleton are innervated by bipolar neurons with their cell bodies close to the cuticle and dendrites attached to it. Numerous efferent fibers synapse with peripheral parts of the mechanosensory neurons, with glial cells surrounding the neurons, and with each other. Most of these efferent fibers are immunoreactive to γ-aminobutyric acid (GABA), and the sensory neurons respond to agonists of ionotropic GABA receptors with a rapid and complete inhibition. In contrast, little is known about metabotropic GABAB receptors that may mediate long-term effects. We investigated the distribution of GABAB receptors on spider leg mechanosensilla using specific antibodies against 2 proteins needed to form functional receptors and an antibody that labels the synaptic vesicles on presynaptic sites. Both anti-GABAB receptor antibodies labeled the distal parts of the sensory cell bodies and dendrites but anti-GABABR1 immunoreactivity was also found in the axons and proximal parts of the cell bodies and some glial cells. The fine efferent fibers that branch on top of the sensory neurons did not show GABAB receptor immunoreactivity but were densely labeled with anti-synapsin and indicated synaptic vesicles on presynaptic locations to the GABAB receptors. Intracellular recordings from sensory neurons innervating the slit sensilla of the spider legs revealed that application of GABAB receptor agonists attenuated voltage-activated Ca2+ current and enhanced voltage-activated outward K+ current, providing 2 possible mechanisms for controlling the neurons' excitability. These findings support the hypothesis that GABAB receptors are present in the spider mechanosensilla where their activation may modulate information transmission.
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Woods, Chris M. C., et Mike J. Page. « Sponge masking and related preferences in the spider crab Thacanophrys filholi (Brachyura : Majidae) ». Marine and Freshwater Research 50, no 2 (1999) : 135. http://dx.doi.org/10.1071/mf98111.
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Spider crabs, Thacanophrys filholi, collected from Kaikoura, New Zealand, were predominantly masked with four species of sponge: Lissodendoryx sp., Iophon laevistylis, Paresperella sp. and Dysidea sp. Other species of sponge, as well as ascidians, brachiopods, anomiid bivalves and tube-dwelling polychaetes, were also part of the extensive epifauna covering the crabs. The act of masking is described, and the location of the hooked setae that allow attachment of material to the crabs exoskeleton is mapped. When crabs in the laboratory were simultaneously offered equal volumes of the four main sponge species with which they masked in the field, they masked equally with Lissodendoryx sp. and Dysidea sp. in preference to I. laevistylis and Paresperella sp. These masking preferences were influenced by the relative volumes in which each species of sponge was presented to the crabs.
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Templin, Julita, et Teresa Napiórkowska. « BIOMETRIC STUDIES ON OLIGOMELIC INDIVIDUALS OF THE SPIDER TEGENARIA ATRICA (ARTHROPODA, ARACHNIDA) / BADANIA BIOMETRYCZNE OSOBNIKÓW OLIGOMELICZNYCH PAJĄKA TEGENARIA ATRICA (ARTHROPODA, ARACHNIDA) ». Zoologica Poloniae 58, no 1-2 (1 décembre 2013) : 19–28. http://dx.doi.org/10.2478/zoop-2013-0002.
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Abstract Oligomely is a type of developmental anomaly occurring in embryos of the spider Tegenaria atrica C.L. Koch under the teratogenic influence of temperature. This anomaly is of metameric origin, as it results from a disorder of metamere formation on the germ band during embryogenesis, resulting in the absence of one half or the whole metamere. In such a case, one or more appendages are missing on one or both sides of the body in a spider leaving a chorion. This anomaly induces changes both in the anatomical structure and exoskeleton of a spider (deformation of carapace and sternum). Carapace length and sternum area were measured, as well as the duration of the subsequent nymph stages of oligomelic individuals with one of the walking appendages missing (always on the right side of the body) was recorded. The consecutive nymph stages of oligomelic individuals lasted for a much shorter time compared with control specimens. This acceleration of development is probably to offset losses incurred during embryogenesis. In the early postembryogenesis, oligomelic specimens exhibited shorter carapace length and smaller surface area of the sternum compared to control individuals, which resulted from the lack of half of the metamere corresponding to the missing leg. However, in older nymph stages, a strong tendency for the faster growth of both carapace and sternum was observed, which can be defined as a compensatory growth increase making up for the losses caused by the anomaly.
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HOMOLA, ELLEN, AMIR SAGI et HANS LAUFER. « Relationship of claw form and exoskeleton condition to reproductive system size and methyl farnesoate in the male spider crab,Libinia emarginata ». Invertebrate Reproduction & ; Development 20, no 3 (décembre 1991) : 219–25. http://dx.doi.org/10.1080/07924259.1991.9672202.
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Blickhan, Reinhard, et Friedrich G. Barth. « Strains in the exoskeleton of spiders ». Journal of Comparative Physiology A 157, no 1 (1985) : 115–47. http://dx.doi.org/10.1007/bf00611101.
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Blickhan, Reinhard, Tom Weihmann et Friedrich G. Barth. « Measuring strain in the exoskeleton of spiders—virtues and caveats ». Journal of Comparative Physiology A 207, no 2 (18 janvier 2021) : 191–204. http://dx.doi.org/10.1007/s00359-020-01458-y.
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AbstractThe measurement of cuticular strain during locomotion using foil strain gauges provides information both on the loads of the exoskeleton bears and the adaptive value of the specific location of natural strain detectors (slit sense organs). Here, we critically review available literature. In tethered animals, by applying loads to the metatarsus tip, strain and mechanical sensitivity (S = strain/load) induced at various sites in the tibia were determined. The loci of the lyriform organs close to the tibia–metatarsus joint did not stand out by high strain. The strains induced at various sites during free locomotion can be interpreted based on S and, beyond the joint region, on beam theory. Spiders avoided laterad loading of the tibia–metatarsus joint during slow locomotion. Balancing body weight, joint flexors caused compressive strain at the posterior and dorsal tibia. While climbing upside down strain measurements indicate strong flexor activity. In future studies, a precise calculation and quantitative determination of strain at the sites of the lyriform organs will profit from more detailed data on the overall strain distribution, morphology, and material properties. The values and caveats of the strain gauge technology, the only one applicable to freely moving spiders, are discussed.
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Philip, Benjamin N., et Cara Shillington. « A Novel Technique of Hair Removal to Examine the Cuticle of Arthropods ». Microscopy Today 15, no 2 (mars 2007) : 22–25. http://dx.doi.org/10.1017/s1551929500050975.
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The highly structured arthropod cuticle is often adorned with dense hairs that conceal the underlying landscape. Thus, to examine the structures and patterns on the cuticle the overlying hairs must be removed with minimal damage to the cuticle itself. Different methods can be employed to eliminate hairs but the difficulty of this task is compounded by the small size and fragility of the exoskeleton to which the hairs are attached. If the hairs are removed using razor blades or scissors, not only is the debris from the cut hairs and the stubble from the remainder of the shaft left behind, but the cuticle is often broken in the course of gripping the exoskeleton. We developed a unique technique that cleanly removes hairs without leaving debris or damaging the structure. This technique has been successfully used to examine the cuticular surfaces of arthropods of varying sizes including spiders, bees, beetles and moths.
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Rudkin, David M., Michael B. Cuggy, Graham A. Young et Deborah P. Thompson. « An Ordovician Pycnogonid (Sea Spider) with Serially Subdivided ‘Head’ Region ». Journal of Paleontology 87, no 3 (mai 2013) : 395–405. http://dx.doi.org/10.1666/12-057.1.
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The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented Silurian specimen. The new taxon,Palaeomarachne granulatan. gen. n. sp., from the Upper Ordovician (ca. 450 Ma) William Lake Konservat-Lagerstätte deposit in Manitoba, Canada, is also the first reported from Laurentia. It is the only record thus far of a fossil sea spider in rocks of demonstrably shallow marine origin. Four incomplete, partially disarticulated molts represent a relatively large, robust animal with a series of five segment-like elements in a ‘head’ region that does not incorporate the first of four preserved limb-bearing trunk segments. This unique pattern may reflect the plesiomorphic condition prior to complete fusion of anterior ‘head’ elements and first trunk segment to form a cephalosoma, as seen in all eupycnogonids.Palaeomarachne granulatais interpreted as occupying a basal stem-group position in the Pycnogonida.
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Politi, Yael, Luca Bertinetti, Peter Fratzl et Friedrich G. Barth. « The spider cuticle : a remarkable material toolbox for functional diversity ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 379, no 2206 (2 août 2021) : 20200332. http://dx.doi.org/10.1098/rsta.2020.0332.
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Engineered systems are typically based on a large variety of materials differing in composition and processing to provide the desired functionality. Nature, however, has evolved materials that are used for a wide range of functional challenges with minimal compositional changes. The exoskeletal cuticle of spiders, as well as of other arthropods such as insects and crustaceans, is based on a combination of chitin, protein, water and small amounts of organic cross-linkers or minerals. Spiders use it to obtain mechanical support structures and lever systems for locomotion, protection from adverse environmental influences, tools for piercing, cutting and interlocking, auxiliary structures for the transmission and filtering of sensory information, structural colours, transparent lenses for light manipulation and more. This paper illustrates the ‘design space’ of a single type of composite with varying internal architecture and its remarkable capability to serve a diversity of functions. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)’.
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Ahl, J. S. B., H. Laufer, A. J. Ahl et P. Takac. « Exoskeletal Abrasion as an Indicator of Reproductive Readiness in the Spider Crab Libinia emarginata ». Journal of Crustacean Biology 16, no 3 (août 1996) : 443. http://dx.doi.org/10.2307/1548733.
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Biaggio, M. Daniela, Iara Sandomirsky, Yael Lubin, Ally R. Harari et Maydianne C. B. Andrade. « Copulation with immature females increases male fitness in cannibalistic widow spiders ». Biology Letters 12, no 9 (septembre 2016) : 20160516. http://dx.doi.org/10.1098/rsbl.2016.0516.
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Copulatory cannibalism of male ‘widow’ spiders (genus Latrodectus ) is a model example of the extreme effects of sexual selection, particularly in L. hasselti and L. geometricus where males typically facilitate cannibalism by females and mate only once. We show that these males can increase their reproductive success by copulating with final-instar, immature females after piercing the female's exoskeleton to access her newly developed sperm storage organs. Females retain sperm through their final moult and have similar fecundity to adult-mated females. This is an adaptive male tactic because immature mating increases insemination success relative to adult mating (which predicts higher paternity) and moreover, rarely ends in cannibalism, so males can mate again. Although successful only during a brief period before the female's final moult, males may employ this tactic when they associate with final-instar females in nature. Consistent with this, one-third of L. hasselti females collected as immatures in nature were already mated. Immature mating alters sexual selection on these otherwise monogynous males, and may explain male traits allowing facultative polygyny in Latrodectus . Since male cohabitation with immature females is common among invertebrates, immature mating may be a widespread, previously unrecognized mating tactic, particularly when unmated females are of high reproductive value.
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Ghislandi, Paolo Giovanni, Maria J. Albo, Cristina Tuni et Trine Bilde. « Evolution of deceit by worthless donations in a nuptial gift-giving spider ». Current Zoology 60, no 1 (1 février 2014) : 43–51. http://dx.doi.org/10.1093/czoolo/60.1.43.
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Abstract Males of the nursery web spider Pisaura mirabilis usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copulation. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that approximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection.
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Legg, David A., Mark D. Sutton, Gregory D. Edgecombe et Jean-Bernard Caron. « Cambrian bivalved arthropod reveals origin of arthrodization ». Proceedings of the Royal Society B : Biological Sciences 279, no 1748 (10 octobre 2012) : 4699–704. http://dx.doi.org/10.1098/rspb.2012.1958.
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Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans (‘great-appendage’ arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming . Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids).
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LEONG, MISHA, MATTHEW A. BERTONE, KEITH M. BAYLESS, ROBERT R. DUNN et MICHELLE D. TRAUTWEIN. « The Exoskeletons in our Closets : A synthesis of research from the ‘Arthropods of our Homes’ project in Raleigh, NC ». Zoosymposia 12, no 1 (25 mars 2018) : 64–68. http://dx.doi.org/10.11646/zoosymposia.12.1.7.
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The history of people living with insects, spiders and their relatives is long, probably as long as humans have been using fixed domiciles (e.g., caves). Studies of caves inhabited by prehistoric people 26,000 years ago suggest arthropod pests already lived alongside our ancestors in those caves (Araújo et al. 2009). Arthropods are also both abundant and diverse in domestic archaeological sites from agricultural civilizations in Egypt, Israel and Europe (Switzerland and Greenland). Arthropods are especially common in association with stored food products and livestock (Panagiotakopulu 2001; Overgaard Nielsen, Mahler, and Rasmussen 2000; Kislev, Hartmann, and Galili 2004).
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Kalvelage, Elisa Maria, Ralf Thomas Voegele et Michael Fischer. « Dissemination of esca-related pathogens in German vineyards : do arthropods play roles in vectoring spores ? » Phytopathologia Mediterranea 60, no 3 (30 décembre 2021) : 467–78. http://dx.doi.org/10.36253/phyto-12948.
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Grapevine Trunk Diseases (GTDs) such as esca challenge viticulture. The main fungal agents of Petri disease or young esca, Phaeomoniella chlamydospora (Pch), diverse Phaeoacremonium species (Pm spp.) and Cadophora luteo-olivacea (Clo), are transmitted to pruning wounds of vines by rain splashes and air currents. Arthropod-mediated dispersal is another possibility for the pathogens to reach pruning wounds. The present study was the first to evaluate possible involvement of arthropods in the dissemination process of esca-related pathogens in German vineyards. Diversity of arthropods on grapevine trunks was determined in 2019 and 2020, using cardboard traps mounted on vine trunks. Captured arthropods were surveyed for the presence of esca-related pathogens on their exoskeletons by using a nested multiplex PCR. In total, 2099 arthropods were examined, of which 35% were positive for Phaeomoniella chlamydospora (Pch), 21% for Phaeoacremonium spp. (Pm), and 7% for Cadophora luteo-olivacea (Clo). Earwigs and spiders were the most prevalent trapped arthropods; Pch was detected on 27% of earwigs and 38% of spiders, Pm spp. on 17 and 19%, and Clo on 3 and 8% of these arthropods. In both years, arthropods carrying the pathogens were already present in April, and therefore within the presumed susceptibility phase of pruned vines. These results indicate involvement of arthropods in the dispersal of esca-related pathogens in German vineyards. Further research, particularly to determine the infection potential of insect-borne fungi, is needed to confirm transmission risk. These results underline the importance of protecting vine pruning wounds to prevent host invasion by GTD pathogens.
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DONOVAN, STEPHEN K. « Contrasting patterns of preservation in a Jamaican cave ». Geological Magazine 154, no 3 (29 mars 2016) : 516–20. http://dx.doi.org/10.1017/s0016756816000182.
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AbstractRed Hills Road Cave, Jamaica is a remnant of a karstic feature quarried away during road building. It is the most important site for Late Pleistocene terrestrial palaeontology on the island. The site is c. 30 ka old. Many taxa were washed in during hurricanes and tropical storms, either as dead carcasses or live organisms that drowned as the cave filled with water. The invertebrate fauna includes snails and arthropods; none are obligate cave dwellers. The 62 species of land snails are the most diverse of any Jamaican cave; operculate taxa may be preserved with the operculum in situ. Arthropods include the only fossil millipedes, isopods and insects (fly puparia, beetle elytra) in the Jamaican fossil record, in addition to land crabs. Millipedes and isopods are well preserved because of a diagenetically early coating of calcite cement. The exoskeletons of these groups contain a small, but significant, calcite component not found in insects, spiders and scorpions. The vertebrate fauna remains understudied, but include: a rodent and three species of bat; a flightless ibis and various other birds; and reptile and amphibian remains. In contrast to the arthropods, the vertebrates are invariably disarticulated apart from rare crania, jawbones retaining teeth and bones that are fused in life. A dead millipede could be coated in calcite when floating in the cave immediately after death; a dead vertebrate carcass would have to rot to expose its bones after the cave dried out and would, most likely, disarticulate before or during the next inundation.
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Eklöf, Johan, Åsa Austin, Ulf Bergström, Serena Donadi, Britas D. H. K. Eriksson, Joakim Hansen et Göran Sundblad. « Size matters : relationships between body size and body mass of common coastal, aquatic invertebrates in the Baltic Sea ». PeerJ 5 (25 janvier 2017) : e2906. http://dx.doi.org/10.7717/peerj.2906.
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Background Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods We collected aquatic, epibenthic macroinvertebrates (>1 mm) in 32 shallow bays along a 360 km stretch of the Swedish coast along the Baltic Sea; one of the largest brackish water bodies on Earth. We then estimated statistical relationships between the body size (length or height in mm), body dry mass and ash-free dry mass for 14 of the most common taxa; five gastropods, three bivalves, three crustaceans and three insect larvae. Finally, we statistically estimated the potential influence of body size on the AFDM/DM ratio per taxon. Results For most taxa, non-linear regression models describing the power relationship between body size and (i) DM and (ii) AFDM fit the data well (as indicated by low SE and high R2). Moreover, for more than half of the taxa studied (including the vast majority of the shelled molluscs), body size had a negative influence on organism AFDM/DM ratios. Discussion The good fit of the modelled power relationships suggests that the constants reported here can be used to quickly estimate organism dry- and ash-free dry mass based on body size, thereby freeing up considerable work resources. However, the considerable differences in constants between taxa emphasize the need for taxon-specific relationships, and the potential dangers associated with ignoring body size. The negative influence of body size on the AFDM/DM ratio found in a majority of the molluscs could be caused by increasingly thicker shells with organism age, and/or spawning-induced loss of biologically active tissue in adults. Consequently, future studies utilizing AFDM/DM (and presumably also AFDM/wet mass) ratios should carefully assess the potential influence of body size to ensure more reliable estimates of organism body mass.
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Cifuentes Sarmiento, Yanira, et Luis Miguel Renjifo. « DIETA DEL CORRELIMOS DIMINUTO (CALIDRIS MINUTILLA) EN CULTIVOS DE ARROZ ORGÁNICO DE COLOMBIA ». Ornitología Neotropical 27 (27 juillet 2016) : 89–96. http://dx.doi.org/10.58843/ornneo.v27i0.61.
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RESUMEN ∙ El arroz es uno de los principales alimentos para el ser humano y su área cultivada global se aproxima a los diez millones de hectáreas. Muchos ecosistemas naturales, en especial humedales, han sido modificados para realizar este cultivo. Sin embargo, el desarrollo de este cereal requiere de etapas de anegamiento que permiten que varios organismos, entre estos las aves playeras, obtengan recursos alimenticios. En los cultivos orgánicos de arroz del Valle del Cauca, Colombia, se han registrado doce especies de aves playeras migratorias provenientes principalmente de Norteamérica y se ha encontrado la mayor concentración de individuos del Correlimos Diminuto (Calidris minutilla) en Colombia. En los sitios de reproducción, C. minutilla se alimenta principalmente de invertebrados bentónicos y terrestres mientras que para los sitios de invernada se ha registrado una mayor gama de presas. Con el fin de determinar la dieta del C. minutilla en arrozales orgánicos, entre octubre y diciembre de 2012 se capturaron 50 individuos con redes de niebla y se les indujo a regurgitar con solución salina. Las presas identificadas en los regurgitados indican que en los arrozales orgánicos del Valle del Cauca, C. minutilla se alimenta principalmente de insectos, arañas y material vegetal. Además, usa pequeñas piedras para triturar presas con exoesqueletos duros como coleópteros y hemípteros. Dado el porcentaje de consumo de larvas y adultos de coleópteros que son considerados una plaga en los cultivos de arroz, C. minutilla puede ser uno de los principales controladores naturales de estos insectos. Esta información contribuye a entender porque C. minutilla utiliza los arrozales y resalta la importancia de este agroecosistema para la migración de esta ave playera.ABSTRACT ∙ Diet of Least Sandpipers (Calidris minutilla) in organic rice fields of ColombiaRice is one of the most important food sources for humans, and its global cultivated surface reaches ten millions of hectares. Many natural ecosystems, especially wetlands, have been modified or destroyed due to conversion to rice fields. However, rice crops require flooding, and the wetlands thus created can provide food for several organisms including shorebirds. In the organic rice fields of Valle del Cauca, in Colombia, twelve species of Nearctic migrant shorebirds have been recorded, including the highest numbers of Least Sandpipers (Calidris minutilla) in Colombia. On their breeding grounds in North America, Least Sandpipers feed on benthic and terrestrial invertebrates, while on the wintering grounds they ingest a wider range of prey. To determine the diet of Least Sandpipers in this type of cultivation in Valle del Cauca, from October 2012 to December 2012 we caught 50 individuals using mist netting and obtained regurgitates induced with saline solution. The identification of prey found in regurgitates indicates that Least Sandpipers feed on insects, spiders, and vegetable material in the study site. In addition, they use small stones to crush prey with hard exoskeleton, such as Coleoptera and Hemiptera. Given the relatively high levels of consumption of beetle larvae and adults, which are considered pests for rice crops, Least Sandpipers could be one of the main biocontrol agents of these insects. This information contributes to understand why Least Sandpipers use organic rice fields and highlights the importance of this agroecosystem for the migration of this shorebird.
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Residori, Sara, Gabriele Greco et Nicola M. Pugno. « The mechanical characterization of the legs, fangs, and prosoma in the spider Harpactira curvipes (Pocock 1897) ». Scientific Reports 12, no 1 (29 juillet 2022). http://dx.doi.org/10.1038/s41598-022-16307-y.
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AbstractThe exoskeleton of spiders is the primary structure that interacts with the external mechanical stimuli, thus playing a crucial role in spider life. In particular, fangs, legs, and prosoma are the main rigid structures of the exoskeleton and their properties must be measured to better understand their mechanical behaviours. Here we investigate, by means of nanoindentation, the mechanical properties of the external sclerotized cuticles of such parts in the spider Harpactira curvipes. Interestingly, the results show that the leg’s cuticle is stiffer than the prosoma and has a stiffness similar to the one of the tip fangs. This could be explained by the legs’ function in perceiving vibrations that could be facilitated by higher stiffness. From a broader perspective, this characterization could help to understand how the same basic material (the cuticle, i.e. mainly composed of chitin) can be tuned to achieve different mechanical functions, which improves the animal’s adaptation to specific evolutive requirements. We, thus, hope that this work stimulates further comparative analysis. Moreover, these results may also be potentially important to inspire the design of graded materials with superior mechanical properties.
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Radosavljevic, Dragoslav, Earl Ada et Rick Hochberg. « Elemental enrichment of the exoskeleton of the whip spider Phrynus marginemaculatus (Arachnida : Amblypygi) ». Journal of Arachnology 49, no 2 (29 juillet 2021). http://dx.doi.org/10.1636/joa-s-20-048.
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Brenneis, Georg, Karina Frankowski, Laura Maaß et Gerhard Scholtz. « The sea spider Pycnogonum litorale overturns the paradigm of the absence of axial regeneration in molting animals ». Proceedings of the National Academy of Sciences 120, no 5 (23 janvier 2023). http://dx.doi.org/10.1073/pnas.2217272120.
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Regenerative abilities and their evolution in the different animal lineages have fascinated generations of biologists. While some taxa are capable of restoring entire individuals from small body fragments, others can regrow only specific structures or lack structural regeneration completely. In contrast to many other protostomes, including the segmented annelids, molting animals (Ecdysozoa) are commonly considered incapable of primary body axis regeneration, which has been hypothesized to be linked to the evolution of their protective cuticular exoskeleton. This holds also for the extraordinarily diverse, segmented arthropods. Contradicting this long-standing paradigm, we here show that immatures of the sea spider Pycnogonum litorale reestablish the posterior body pole after transverse amputation and can regrow almost complete segments and the terminal body region, including the hindgut, anus, and musculature. Depending on the amputation level, normal phenotypes or hypomeric six-legged forms develop. Remarkably, also the hypomeric animals regain reproductive functionality by ectopic formation of gonoducts and gonopores. The discovery of such complex regenerative patterns in an extant arthropod challenges the hitherto widely assumed evolutionary loss of axial regeneration during ecdysozoan evolution. Rather, the branching of sea spiders at the base of Chelicerata and their likely ancestral anamorphic development suggests that the arthropod stem species may have featured similar regenerative capabilities. Accordingly, our results provide an incentive for renewed comparative regeneration studies across ecdysozoans, with the aim to resolve whether this trait was potentially even inherited from the protostome ancestor.
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Rößler, Daniela C., Kris Kim, Massimo De Agrò, Alex Jordan, C. Giovanni Galizia et Paul S. Shamble. « Regularly occurring bouts of retinal movements suggest an REM sleep–like state in jumping spiders ». Proceedings of the National Academy of Sciences 119, no 33 (8 août 2022). http://dx.doi.org/10.1073/pnas.2204754119.
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Sleep and sleep-like states are present across the animal kingdom, with recent studies convincingly demonstrating sleep-like states in arthropods, nematodes, and even cnidarians. However, the existence of different sleep phases across taxa is as yet unclear. In particular, the study of rapid eye movement (REM) sleep is still largely centered on terrestrial vertebrates, particularly mammals and birds. The most salient indicator of REM sleep is the movement of eyes during this phase. Movable eyes, however, have evolved only in a limited number of lineages—an adaptation notably absent in insects and most terrestrial arthropods—restricting cross-species comparisons. Jumping spiders, however, possess movable retinal tubes to redirect gaze, and in newly emerged spiderlings, these movements can be directly observed through their temporarily translucent exoskeleton. Here, we report evidence for an REM sleep–like state in a terrestrial invertebrate: periodic bouts of retinal movements coupled with limb twitching and stereotyped leg curling behaviors during nocturnal resting in a jumping spider. Observed retinal movement bouts were consistent, including regular durations and intervals, with both increasing over the course of the night. That these characteristic REM sleep–like behaviors exist in a highly visual, long-diverged lineage further challenges our understanding of this sleep state. Comparisons across such long-diverged lineages likely hold important questions and answers about the visual brain as well as the origin, evolution, and function of REM sleep.
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Machałowski, Tomasz, Chris Amemiya et Teofil Jesionowski. « Chitin of Araneae origin : structural features and biomimetic applications : a review ». Applied Physics A 126, no 9 (6 août 2020). http://dx.doi.org/10.1007/s00339-020-03867-x.
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Abstract Large scale isolation of chitin traditionally has been carried out from fungal biomass as well as from seafood processing wastes, e.g., from shrimp, crab and lobster exoskeletons. Despite the relative abundance and ready availability of these materials, isolation of chitin requires great deal of chemical reagents and is time consuming. Obtained in this way chitin is produced in the form of powders, whiskers, and flakes. In this review, we have focused on the moulting cuticles of spiders as an alternative source of naturally occurring chitin. The comparatively high chitin content in the moults allows for rapid preparation of structures that maintain their original shape and integrity, such as the chitinous tubes from leg exoskeletons. Based on our latest scientific analyses regarding spider chitin, we highlight here its advantages and its biomimetic applications in tissue engineering, catalysis and environmental science.
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« EXOSKELETAL ABRASION AS AN INDICATOR OF REPRODUCTIVE READINESS IN THE SPIDER CRAB LIBINIA EMARGINATA ». Journal of Crustacean Biology 16, no 3 (1 janvier 1996) : 443–47. http://dx.doi.org/10.1163/193724096x00450.
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