Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spiders”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2000

Microbial production of spider silk proteins.

The remarkable properties of spider dragline silk and related protein polymers will find many applications if the materials can be produced economically. We have demonstrated the production of high molecular weight spider dragline silk analog proteins encoded by synthetic genes in several microbial systems, including Escherichia coli and Pichia pastoris. In E. coli, proteins of up to 1000 amino acids in length could be produced efficiently, but the yield and homogeneity of higher molecular weight silk proteins were found to be limited by truncated synthesis, probably as a result of ribosome termination errors. No such phenomenon was observed in the yeast P. pastoris, where higher molecular weight silk proteins could be produced without heterogeneity due to truncated synthesis. Spider dragline silk analog proteins could be secreted by P. pastoris when fused to both the signal sequence and N-terminal pro-sequence of the Saccharomyces cerevisiae alpha-mating factor gene.

Amino Acid Sequence↗
PubMed2002

[The attraction of silk: base of group cohesion and collective behavior in social spiders].

Social spiders differ from social insects by the production and the use of silk to build irregular webs. This silk prevents dispersion of the individuals and ensures the group cohesion during swarming and collective displacements, playing a part similar to tracks of pheromones in ants. A social spider Anelosimus eximius is attracted by conspecific silk and does not show any discrimination relative to its origin, excluding any group closure. The quantity of silk and the state of satiety of the individual modulate this attraction, and might explain how the spider society adapts the size of the web to its nutritional needs.

Animals↗
PubMed2005

Araneoid egg case silk: a fibroin with novel ensemble repeat units from the black widow spider, Latrodectus hesperus.

Araneoid spiders use specialized abdominal glands to manufacture up to seven different protein-based silks/glues that have diverse physical properties. The fibroin sequences that encode egg case fibers (cover silk for the egg case sac) and the secondary structure of these threads have not been previously determined. In this study, MALDI tandem TOF mass spectrometry (MS/MS) and reverse genetics were used to isolate the first egg case fibroin, named tubuliform spidroin 1 (TuSp1), from the black widow spider, Latrodectus hesperus. Real-time quantitative PCR analysis demonstrates TuSp1 is selectively expressed in the tubuliform gland. Analysis of the amino acid composition of raw egg case silk closely aligns with the predicted amino acid composition from the primary sequence of TuSp1, which supports the assertion that TuSp1 represents a major component of egg case fibers. TuSp1 is composed of highly homogeneous repeats that are 184 amino acids in length. The long stretches of polyalanine and glycine-alanine subrepeats, which account for the crystalline regions of minor ampullate and major ampullate fibers, are very poorly represented in TuSp1. However, polyserine blocks and short polyalanine stretches were highly iterated within the primary sequence, and (13)C NMR spectroscopy demonstrated that the majority of alanine was found in a beta-sheet structure in post-spun egg case silk. The TuSp1 repeat unit does not display substantial sequence similarity to any previously described fibroin genes or proteins, suggesting that TuSp1 is a highly divergent member of the spider silk gene family.

Amino Acid Sequence↗
PubMed2006

Novel molecular and mechanical properties of egg case silk from wasp spider, Argiope bruennichi.

Araneoid spiders use specialized abdominal glands to produce up to seven different protein-based silks/glues that have various mechanical properties. To date, the fibroin sequences encoding egg case fibers have not been fully determined. To gain further understanding of a recently reported spider silk protein gene family, several novel strategies were utilized in this study to isolate two full-length cDNAs of egg case silk proteins, cylindrical silk protein 1 (CySp1, 9.1 kb) and cylindrical silk protein 2 (CySp2, 9.8 kb), from the wasp spider, Argiope bruennichi. Northern blotting analysis demonstrated that CySp1 and CySp2 are selectively expressed in the cylindrical glands. The amino acid composition of raw egg case silk was closely consistent with the deduced amino acid composition based on the sequences of CySp1 and CySp2, which supports the assertion that CySp1 and CySp2 represent two major components of egg case silk. CySp1 and CySp2 are primarily composed of remarkable homogeneous assemble repeats that are 180 residues in length and consist of several complex subrepeats, and they contain highly homologous C-termini and markedly different N-termini. Our results suggest a possible link between CySp1 and CySp2. In addition, comparisons of stress/strain curves for dragline and egg case silk from Argiope bruennichi showed obvious differences in ultimate strength and extensibility, and similarities in toughness.

Amino Acid Sequence↗
PubMedDate not supplied

Spider silk protein refolding is controlled by changing pH.

Spidroins, the major silk proteins making up the spider's dragline silk, originate in two distinct tissue layers (A and B) in the spider's major ampullate gland. Formation of the complex thread from spidroins occurs in the lumen of the duct connected to the gland. Using pH-sensitive microelectrode probes, we showed that the spidroins traveling through the gland and duct experience a monotonic decrease in pH from 7.2 to 6.3. In addition, circular dichroism spectroscopy of material extracted from the gland showed a structural refolding concomitant with position in the gland and post-extraction changes in pH. We demonstrate that lowering the pH in vitro causes a dramatic conformational change in the protein from the A zone, converting it irreversibly from a coil to a predominantly beta-sheet structure. Furthermore, amino acid analyses have indicated that there are at least two distinct, though similar, proteins secreted in the A and B zones suggesting a potential factor in the progressive acidification as well as a pH sensitivity of the folding of spidroins in the gland. Thus, we provide, for the first time, a quantitative map of the pH value and position correlated with molecular structural folding in the silk gland characterizing the crucial role that pH plays in spider silk formation.

Animals↗
PubMed2006

N-terminal nonrepetitive domain common to dragline, flagelliform, and cylindriform spider silk proteins.

Spider silk has been extensively studied for its outstanding mechanical properties. Partial intermediate and C-terminal sequences of different spider silk proteins have been determined, and during the past decade also N-terminal domains have been characterized. However, only some of these N-terminal domains have been reported to contain signal peptides, leaving the mechanism whereby they enter the secretory pathway open to speculation. Here we present the sequence of a 394-residue N-terminal region of the Euprosthenops australis major ampullate spidroin 1 (MaSp1). A close comparison with published sequences from other species revealed the presence of N-terminal signal peptides followed by an approximately 130-residue nonrepetitive domain. From secondary structure predictions, helical wheel analysis, and circular dichroism spectroscopy this domain is concluded to contain five alpha-helices and is a conserved constituent of hitherto analyzed dragline, flagelliform, and cylindriform spider silk proteins.

Amino Acid Sequence↗
PubMed2003

Contrasting allozyme and RAPD variation in spider populations from patchy forest habitats.

During the last 1000 years, massive deforestation events have occurred in Flanders (the northern part of Belgium) and the remaining forests have become very isolated patches. It is expected that organisms bound to these patchy forest habitats and with limited dispersal capacities will likely experience strong effects of genetic drift. One such organism is the spider Coelotes terrestris. Allozyme data suggested that 10 Flemish populations of this spider showed little genetic variation, as only one out of 20 loci was polymorphic (phosphoglucose isomerase). In view of this result, we used random amplified polymorphic DNA (RAPD) markers to test whether this lack of allozyme diversity is an inherent feature of the populations and/or species studied or whether it rather reflects a characteristic of the markers and/or methods used. Since the RAPD data revealed a substantial amount of genetic diversity in the same 10 populations, our results suggest that the latter is true. Furthermore, the RAPD data agree with the expectations for an organism with low dispersal capacities that has lived in isolated forest patches for at least 200 generations. Supplemented with the results of other techniques and studies, these findings might be of importance for the future conservation of this spider species in Flanders.

Animals↗
PubMed2004

Sex pheromone components of the bronzed cutworm, Nephelodes minians, a prey species of a bolas spider, Mastophora hutchinsoni.

The bolas spider, Mastophora hutchinsoni, attracts adult males of four species of moths by aggressively mimicking their sex pheromone. Here, we report the identification of two sex pheromone components of one of these species, the bronzed cutworm, Nephelodes minians. Simultaneous gas chromatographic (flame ionization detection) and electroantennographic detection (EAD) analysis of extracts of the sex pheromone glands of female N. minians indicated two components eliciting strong EAD responses from a conspecific male antenna that corresponded in retention time with (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-11-hexadecenyl acetate (Z11-16:OAc), using both polar and nonpolar columns. Mass spectra of these two peaks were identical to those of synthetic Z11-16:Ald and Z11-16:OAc. The double-bond positions were confirmed by GC-MS analysis of dimethyl disulfide derivatives of the putative pheromone components. In a field test, a 5:1 blend of Z11-16:Ald to Z11-16:OAc attracted male N. minians. Overall, there is no overlap in the chemical constituents of the sex pheromones of three moth species preyed upon by this bolas spider for which pheromones have now been identified. These studies suggest that bolas spiders are versatile in their ability to synthesize semiochemicals for different prey species. This versatility may be advantageous to a predator that has an otherwise extremely specialized hunting tactic.

Acetates↗
PubMed2005

A pictorial version of the Extrinsic Affective Simon Task: sensitivity to generally affective and phobia-relevant stimuli in high and low spider fearful individuals.

This study assessed whether a pictorial, rather than a verbal, Extrinsic Affective Simon Task (EAST: De Houwer, 2003) is, 1) sensitive to the affective valence of normatively positive, neutral, and negative pictures, 2) sensitive to interindividual differences pertaining to fear-relevant affective associations, and 3) a valid predictor for strategic and/or reflexive fear responses. High (n = 35) and low (n = 35) spider fearful individuals completed an EAST comprising of universal positive, negative, neutral, and spider pictures. The pictorial EAST was sensitive to normatively valenced stimuli, tended to differentiate between high and low fearful individuals with respect to spider pictures, and showed independent predictive validity for avoidance behavior.

Adult↗
PubMed1992

Covariation detection in treated and untreated spider phobics.

Twenty treated and 18 untreated spider phobics were exposed to a series of 72 slides. Three different categories of slides were used: phobia-relevant slides (spiders), alternative fear-relevant slides (weapons), and neutral slides (flowers). Slides were randomly paired with either a shock, a tone, or nothing at all. Despite the absence of a systematic correlation between slides and outcomes, untreated phobics strongly overestimated the covariation between spider slides and shock. Treated phobics did not show a covariation bias, suggesting that such bias can be modulated by behavioral treatment. In addition, untreated subjects were more confident about their contingency estimates than were treated subjects. The present results fit with earlier studies.

Adolescent↗
PubMed2006

Biopolymers: shape memory in spider draglines.

The ductility and strength of spider draglines means that they outperform the best synthetic fibres, but surprisingly little is known about the torsional properties of this remarkable filament. Unlike a mountain climber swinging from a rope, a spider suspended from its silk thread hardly ever twists. Here we show that a spider dragline has a torsional shape 'memory' in that it can reversibly and totally recover its initial form without any external stimulus; its observed relaxation dynamics indicate that these biological molecules have successively different torsional constants.

Animals↗
PubMed2001

Production of spider silk proteins in tobacco and potato.

Spider dragline silk is a proteinaceous fiber with remarkable mechanical properties that make it attractive for technical applications. Unfortunately, the material cannot be obtained in large quantities from spiders. We have therefore generated transgenic tobacco and potato plants that express remarkable amounts of recombinant Nephila clavipes dragline proteins. Using a gene synthesis approach, the recombinant proteins exhibit homologies of >90% compared to their native models. Here, we demonstrate the accumulation of recombinant silk proteins, which are encoded by synthetic genes of 420-3,600 base pairs, up to a level of at least 2% of total soluble protein in the endoplasmic reticulum (ER) of tobacco and potato leaves and potato tubers, respectively. Using the present expression system, spider silk proteins up to 100 kDa could be detected in plant tissues. When produced in plants, the recombinant spidroins exhibit extreme heat stability-a property that is used to purify the spidroins by a simple and efficient procedure.

Amino Acid Sequence↗
PubMed2003

Involvement of Notch and Delta genes in spider segmentation.

It is currently debated whether segmentation in different animal phyla has a common origin and shares a common genetic mechanism. The apparent use of different genetic networks in arthropods and vertebrates has become a strong argument against a common origin of segmentation. Our knowledge of arthropod segmentation is based mainly on the insect Drosophila, in which a hierarchical cascade of transcription factors controls segmentation. The function of some of these genes seems to be conserved among arthropods, including spiders, but not vertebrates. The Notch pathway has a key role in vertebrate segmentation (somitogenesis) but is not involved in Drosophila body segmentation. Here we show that Notch and Delta genes are involved in segmentation of another arthropod, the spider Cupiennius salei. Expression patterns of Notch and Delta, coupled with RNA interference experiments, identify many similarities between spider segmentation and vertebrate somitogenesis. Our data indicate that formation of the segments in arthropods and vertebrates may have shared a genetic programme in a common ancestor and that parts of this programme have been lost in particular descendant lineages.

Animals↗
PubMed2002

Population genetics of wolf spiders of fragmented habitat in the wheat belt of New South Wales.

Possible effects of habitat fragmentation on the population genetics of a species of wolf spider (Lycosidae) from remnant Callitris woodland in the wheat belt of central western New South Wales in Australia are examined. Single-strand conformational analysis of mitochondrial cytochrome oxidase (subunit 1) was used to characterize the haplotypes of 295 spiders in six blocks each of four woodland sites. DNA sequences were collected from 119 of these spiders to confirm haplotype scoring, allow phylogeny estimation and permit calculation of sequence-based statistics. Intra-block tests do not suggest widespread effects of fragmentation. Genetic diversity is high in all blocks, with 25 haplotypes being identified. Nucleotide diversity is relatively low, as all of the haplotypes are closely related. One block had a significantly low value for the Ewens/Watterson test of neutrality and one block's value was nearly significantly high. Two blocks had nearly significant values of the Harpending Raggedness Index testing for recent population bottlenecks. No other intrablock tests approach significance. Interpopulation comparisons show significant nonhomogeneity of haplotype frequencies globally and in all pairwise comparisons. Relationships between woodland blocks based on haplotype frequencies are discordant with geographical proximity. Haplotype distribution patterns suggest that population structuring existed prior to fragmentation. We develop two measures of genetic distinctiveness to identify subpopulations of interest for conserving evolutionary processes in a species' regional population. One is based on the sum of pairwise FST values and one on the spatial distribution of genetic variation. High values of the measure suggest a subpopulation might have been recently perturbed and low values that it is relatively undisturbed. The two measures identify different blocks as being of particular interest.

Animals↗
PubMed1999

Polypeptide neurotoxins from spider venoms.

Spider venoms contain a variety of toxic components. The polypeptide toxins are divided into low and high molecular mass types. Small polypeptide toxins interacting with cation channels display spatial structure homology. They can affect the functioning of calcium, sodium, or potassium channels. A family of high molecular mass toxic proteins was found in the venom of the spider genus Latrodectus. These neurotoxins, latrotoxins, cause a massive transmitter release from a diversity of nerve endings. The latrotoxins are proteins of about 1000 amino acid residues and share a high level of structure identity. The structural and functional properties of spider polypeptide toxins are reviewed in this paper.

Amino Acid Sequence↗
PubMed2002

Peripheral GABAergic inhibition of spider mechanosensory afferents.

Spider mechanosensory neurons receive an extensive network of efferent synapses onto their sensory dendrites, somata and distal axonal regions. The function of these synapses is unknown. Peripheral synapses are also found on crustacean stretch-receptor neurons but not on mechanosensory afferents of other species, although inhibitory GABAergic synapses are a common feature of centrally located axon terminals. Here we investigated the effects of GABA receptor agonists and antagonists on one group of spider mechanosensory neurons, the slit sense organ VS-3, which are accessible to current- and voltage-clamp recordings. Bath application of GABA activated an inward current that depolarized the membrane and increased the membrane conductance leading to impulse inhibition. VS-3 neuron GABA receptors were activated by muscimol and inhibited by picrotoxin but not bicuculline, and their dose-response relationship had an EC(50) of 103.4 microm, features typical for insect ionotropic GABA receptors. Voltage- and current-clamp analysis confirmed that, while the Na(+) channel inhibition resulting from depolarization can lead to impulse inhibition, the increase in membrane conductance (i.e. 'shunting') completely inhibited impulse propagation. This result argues against previous findings from other preparations that GABA-mediated inhibition is caused by a depolarization that inactivates Na(+) conductance, and it supports those findings that assign this role to membrane shunting. Our results show that GABA can rapidly and selectively inhibit specific mechanoreceptors in the periphery. This type of peripheral inhibition may provide spiders with a mechanism for distinguishing between signals from potential prey, predators or mates, and responding with appropriate behaviour to each signal.

Afferent Pathways↗
PubMedDate not supplied

Spider web survey or whole plant visual sampling? Impact assessment of Bt corn on non-target predatory insects with two concurrent methods.

Impact assessment studies rely on relevant sampling methods. Correct evaluation of methods can be done by their concurrent use in the same sampling site and period. Collecting webs of Theridion impressum L. Koch (Araneae: Theridiidae) may serve as an arthropod sampling method: empty cuticles of prey items remain attached to the back side of the leaves with adhesive silk. Our study aimed to compare the applicability of the two methods concurrently (spider web survey and whole plant visual sampling) in a risk assessment study. The spider web survey recorded more predatory insect families than the whole plant visual sampling. Both methods were able to detect significant differences in the quantity of predatory insects in Bt vs. isogenic plots, but not in the same taxa (Nabidae: spider-web, 2001, Bt > Iso; Coccinellidae: plant sampling, 2001, Iso > Bt; Welsh-test, P < 0.05); thus, they could not confirm each other. The lack of confirmation can be explained by differences in the sensitivity and selectivity of the two methods. A web survey of T. impressum has the practical advantage that although we concentrate only on the one species during field sampling, we gain additional information on a wide range of foliage-dwelling arthropods. Due to several biological uncertainties, interpretation and explanation of the results remain problematic. Thus, additional research--based on in-situ observation and recording of T. impressum-prey interactions--is necessary before we could propose web survey method as a complementary tool in ecological impact assessment.

Animals↗
PubMed2005

A spider that feeds indirectly on vertebrate blood by choosing female mosquitoes as prey.

Spiders do not feed directly on vertebrate blood, but a small East African jumping spider (Salticidae), Evarcha culicivora, feeds indirectly on vertebrate blood by choosing as preferred prey female mosquitoes that have had recent blood meals. Experiments show that this spider can identify its preferred prey by sight alone and by odor alone. When presented with two types of size-matched motionless lures, E. culicivora consistently chose blood-fed female mosquitoes in preference to nonmosquito prey, male mosquitoes, and sugar-fed female mosquitoes (i.e., females that had not been feeding on blood). When the choice was between mosquitoes of different sizes (both blood- or both sugar-fed), small juveniles chose the smaller prey, whereas adults and larger juveniles chose the larger prey. However, preference for blood took precedence over preference for size (i.e., to get a blood meal, small individuals took prey that were larger than the preferred size, and larger individuals took prey that were smaller than the preferred size). When presented with odor from two prey types, E. culicivora approached the odor from blood-fed female mosquitoes significantly more often the odor of the prey that were not carrying blood.

Animals↗