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At least 505 records · Page 28Linked to original sources
PubMed1976

Web-building time in a spider: preliminary applications of ultrasonic detection.

Data collection on time and length of building in orb-weaving spiders has suffered from absence of light during construction and inconvenient hours. A simple apparatus is described which permits recording of the spiders' movements as they disturb an ultrasonic field. By varying onset and length of dark periods for two animals at even temperature and by registering the building periods for 127 webs, a definite influence of the light-dark cycle can be identified: there is a strong preference for building webs in the dark; this is superimposed on the circadian rhythm of orb-web construction. One of the spiders always built earlier than the other.

Animals↗
PubMed1993

Quantitative analysis of spider locomotion employing computer-automated video tracking.

The locomotor activity of adult specimens of the wolf spider Pardosa amentata was measured in an open-field setup, using computer-automated colour object video tracking. The x,y coordinates of the animal in the digitized image of the test arena were recorded three times per second during four consecutive 12-h periods, alternating between white and red (lambda > 600 nm) illumination. Male spiders were significantly more locomotor active than female spiders under both lighting conditions. They walked, on average, twice the distance of females, employed higher velocities, and spent less time in quiescence. Both male and female P. amentata were significantly less active in red light (simulated dark environment) than in white light. The results also revealed that P. amentata administers its walking velocity and periods of quiescence according to consistent distributions, which can be approximated by simple mathematical expressions. It was found that this species spends exponentially decreasing time at increasing velocities. The number of quiescent periods, however, follow a power decay distribution at increasing quiescent period duration.

Acceleration↗
PubMed1975

Fine structure of tarsal sensory organs in the whip spider Admetus pumilio (Amblypygi, Arachnida).

The sensory organs on the tarsi of the antenniform first legs of the whip spider Admetus pumilio C. L. Koch (Amblypygi, Arachnida) were examined with the scanning and transmission electron microscope. At least four different types of hair sensilla were found: (1) thick-walled bristles, which have the characteristics of contact chemoreceptors (several chemoreceptive dendrites in the lumen plus two mechanoreceptors at the base); (2) short club sensilla, innervated by 4-6 neurons which terminate in a pore on the tip; they are possibly humidity receptors; (3) porous sensilla, which are either innervated by 20-25 neurons and have typical pore tubules, or they have 40-45 neurons but no pore tubules; both types are considered to be olfactory; (4) rod sensilla occur in clusters near segmental borders; they are innervated by only one large dendrite which branches inside the lumen. Other tarsal receptors are the claws, which correspond to contact chemoreceptors, and the pit organ which resembles the tarsal organ of spiders. Compared to other arthropod sensilla, the contact chemoreceptors are very similar to those of spiders, while the porous sensilla correspond structurally to olfactory receptors in insects; the club and rod sensilla seem to be typical for amblypygids.

Animals↗
PubMed1990

Wolf spider bites in São Paulo, Brazil: a clinical and epidemiological study of 515 cases.

Data obtained from 515 victims of bites of wolf spiders (family Lycosidae) who were attended in Vital Brazil Hospital, São Paulo City, Brazil, in a 5-year period (1979-1983) were analysed. Bites were more frequent in males (56%). All age groups were involved. Foot and hand were the preferential sites of bite (79%), and pain, generally mild, was the predominant symptom (83%). No local necrosis, a severe complication described in the previous literature, was detected, suggesting that those old cases were due to misdiagnosed Loxosceles spider bites. Specific antivenom was employed in only three cases which is evidence that physicians do not consider wolf spider bites to be severe.

Adolescent↗
PubMed1987

Inhibitory effect of 2,4-dihydroxyphenylacetylasparagine, a common moiety of spider toxin, on glutamate binding to rat brain synaptic membranes.

2,4-Dihydroxyphenylacetylasparagine (2,4-DHPA-ASN), a common moiety of molecules of spider toxins, was shown to inhibit L-[3H]glutamic acid binding to rat brain synaptic membranes in a dose-dependent manner. The inhibitory effect of 2,4-DHPA-ASN was almost the same as that of intact spider toxin isolated from Nephila clavata, but significantly higher than that of 2,4-dihydroxyphenylacetic acid (2,4-DHPA). In addition, neither 2,4-dihydroxybenzoic acid nor the isomers of 2,4-DHPA suppressed the glutamate binding. These results suggested that 2,4-DHPA might be the functional part and asparagine in the molecules of spider toxins seemed to cause increasing affinity toward the recognition site of glutamate binding.

Animals↗
PubMed1982

The activities of enzymes associated with anaerobic pathways, glycolysis and the Krebs cycle in spiders.

1. The activities of eight enzymes that participate in or are closely linked to anaerobic glycolysis or the krebs cycle were measured in 11 species of spiders representing diverse taxonomic groups (Table 1). 2. The results indicate three anaerobic pathways may operate in spiders. The major pathway leads to the accumulation of D-lactate and one of the minor pathways to alanine and malate as postulated by Linzen & Gallowitz (1975). Another minor pathway ends with the accumulation of glycerol-3-phosphate and pyruvate (Fig 1). 3. There were no consistent correlations between the degree of development of certain pathways or enzyme activities and a spider's habits and respiratory exchange system. 4. Lactate pathways are much more highly developed in the legs and cephalothorax than in the abdomen.

Anaerobiosis↗
PubMed1988

Effect of spider venom on cochlear nerve activity consistent with glutamatergic transmission at hair cell-afferent dendrite synapse.

Venom from the spider Argiope trifasciata, a highly specific blocker of the ionic channels associated with invertebrate glutamatergic receptors, was perfused through scala tympani of the basal turn of the pig cochlea. Its effect on spontaneous and driven activity of single afferent neurons was studied. 0.1 U/ml spider venom altered the maximum driven activity without an effect on spontaneous activity. 1 U/ml spider venom suppressed both spontaneous and driven activity. These findings are consistent with the hypothesis that L-glutamate is the neurotransmitter of the synapse between inner hair cells and primary auditory afferent neurons. The results also suggest that the differences in spontaneous activity between neurons may originate in variations in neurotransmitter release.

Animals↗
PubMed1989

Life extension by dietary restriction in the bowl and doily spider, Frontinella pyramitela.

Longevity of free-living female adult bowl and doily spiders was compared with that of captive spiders fed at dietary regimes of one, three, and five Drosophila melanogaster per week. Adult females lived, on average, only 8 days in the field and the pattern of survivorship showed no evidence that senescence contributed to mortality. In the laboratory, mean adult life span was 81.3, 63.9, and 42.3 days on the one, three, and five Drosophila diets, respectively. Decreased feeding rate also delayed egg laying and reduced total fecundity. Survival and reproductive patterns indicated the manifestation of spider senescence at all laboratory feeding levels, with a younger onset of senescence at the higher feeding rates.

Animals↗
PubMed2006

Astacin family metallopeptidases and serine peptidase inhibitors in spider digestive fluid.

Digestive fluid of the araneid spider Argiope aurantia is known to contain zinc metallopeptidases. Using anion-exchange chromatography, size-exclusion chromatography, sucrose density gradient centrifugation, and gel electrophoresis, we isolated two lower-molecular-mass peptidases, designated p16 and p18. The N-terminal amino acid sequences of p16 (37 residues) and p18 (20 residues) are 85% identical over the first 20 residues and are most similar to the N-terminal sequences of the fully active form of meprin (beta subunits) from several vertebrates (47-52% and 50-60% identical, respectively). Meprin is a peptidase in the astacin (M12A) subfamily of the astacin (M12) family. Additionally, a 66-residue internal sequence obtained from p16 aligns with the conserved astacin subfamily domain. Thus, at least some spider digestive peptidases appear related to astacin of decapod crustaceans. However, important differences between spider and crustacean metallopeptidases with regard to isoelectric point and their susceptibility to hemolymph-borne inhibitors are demonstrated. Anomalous behavior of the lower-molecular-mass Argiope peptidases during certain fractionation procedures indicates that these peptidases may take part in reversible associations with each other or with other proteins. A. aurantia digestive fluid also contains inhibitory activity effective against insect digestive peptidases. Here we present evidence for at least thirteen, heat-stable serine peptidase inhibitors ranging in molecular mass from about 15 to 32 kDa.

Amino Acid Sequence↗
PubMed2004

Web-building management in an orb-weaving spider, Zygiella x-notata: influence of prey and conspecifics.

According to optimal foraging theory, spiders should adapt their web building to environmental variations. Until now, there was no data on the influence of simultaneous information coming from different environmental factors on web building behaviour. Under laboratory conditions, we studied the behaviour of Zygiella x-notata in the presence of prey, conspecifics, or both simultaneously. There was a stimulating effect of prey, but web building was not affected by the presence of conspecifics. When spiders and prey were present simultaneously, the effect was similar to that of prey alone; it seemed that there was no interactive influence of both factors. We discussed about the use of environmental information by spiders in foraging behaviour.

Animals↗
PubMed2004

Lattice deformation and thermal stability of crystals in spider silk.

The X-ray diffraction of dragline silks, produced by Nephila and Cyrtophora spiders, were measured by synchrotron radiation in their original states or in situ during stretching and heating. Nephila pilipes spiders construct a two-dimensional orb web that must be rebuilt in one or 2 days, but Cyrtophora spiders form a three-dimensional tent web that can exist for several weeks in a tropical forest. Diffraction patterns of N. pilipes and Cyrtophora draglines resemble each other. Crystals of two kinds are identified in these draglines; one is aligned parallel to the silk direction and another is less oriented. The less oriented crystal in Cyrtophora dragline is aligned better than that in N. pilipes dragline, which generates about three times stronger diffract intensity. Crystals in N. pilipes and C. moluccensis dragline silks have remarkable thermal stability. Equatorial reflections remain undiminished until 350 and 450 degrees C for N. pilipes and C. moluccensis, respectively. In contrast, the meridional reflections S and (002), which are parallel to the silk thread, disappear at a temperature less than 100 degrees C for C. moluccensis but remain for Nephila up to 100 degrees C. Meridional reflections S and (002) shift to a smaller angle during stretching, whereas equatorial reflections remain constant in a range 1.0-1.3 times the original length. The position of the S reflection shifts rapidly in the first 10% of elongation from the original length but remains constant during subsequent stretching, whereas the (002) reflection shifts rapidly during the first 5% elongation from the original length and continues to shift subsequently. In contrast, the features of N. pilipes dragline alter insignificantly during stretching. Examination of the composition of amino acids of the draglines of N. pilipes and C. moluccensis indicates that a dragline of N. pilipes contains more glycine, but much less alanine, than that of C. moluccensis.

Amino Acids↗
PubMed2004

A naturalistic examination of positive expectations, time course, and disgust in the origins and reduction of spider and insect distress.

We used a naturalistic method to examine the causes of changes in individuals' reactions to, and feelings about, spiders and insects. In this descriptive retrospective study, 50 college students who reported substantial changes in their attitudes toward spiders and/or insects (in the absence of professional treatment) underwent telephone interviews about the change process. We found that individuals frequently describe the role of positive experiences and expectations in positive change and some individuals report sudden changes. Further, descriptions of the important role of disgust in the change process were common. We discuss the implications of our findings for understanding the etiology and treatment of spider and insect distress and make a case for the usefulness of naturalistic methods in expanding scientific knowledge.

Adult↗
PubMed2006

To look or not to look at threat? Scanpath differences within a group of spider phobics.

Predicting the behavior of phobic patients in a confrontational situation is challenging. While avoidance as a major clinical component of phobias suggests that patients orient away from threat, findings based on cognitive paradigms indicate an attentional bias towards threat. Here we present eye movement data from 21 spider phobics and 21 control subjects, based on 3 basic oculomotor tasks and a visual exploration task that included close-up views of spiders. Relative to the control group, patients showed accelerated reflexive saccades in one of the basic oculomotor tasks, while the fear-relevant exploration task evoked a general slowing in their scanning behavior and pronounced oculomotor avoidance. However, this avoidance strongly varied within the patient group and was not associated with the scores from spider avoidance-sensitive questionnaire scales. We suggest that variation of oculomotor avoidance between phobics reflects different strategies of how they cope with threat in confrontational situations.

Adult↗
PubMed2005

Activation and measurement of threat associations in fear of spiders: an application of the Extrinsic Affective Simon Task.

The Extrinsic Affective Simon Task (DeHouwer, EAST; Experimental Psychol. 50 (2003) 77) was used to assess how different context conditions lead to differential activation of cognitive schemata in anxiety. Participants completed two identical EASTs, in which ambiguous target words (e.g., legs, net) were categorized together with pleasant words and unpleasant, fear-related words. Each EAST was preceded by the presentation of pictures, activating either a 'human' concept or a 'spider' concept. Results indicated that spider fearful participants showed threat associations towards the target words, but only when the spider concept was primed. Non-fearful participants did not show threat associations with either type of priming. We conclude that impact of threat associations depends on the activated context, and that the EAST is suitable for the assessment of fear associations and their current activation level.

Animals↗
PubMed2004

Antifreeze proteins in Alaskan insects and spiders.

Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods from the Arctic or anywhere in Alaska. The hemolymph of 75 species of insects and six spiders from interior and arctic Alaska were screened for thermal hysteresis (a difference between the freezing and melting points), characteristic of the presence of AFPs. Eighteen species of insects and three spiders were shown to have AFPs. Ten of the insects with AFPs were beetles including the first species from the families Chrysomelidae, Pythidae, Silphidae and Carabidae. In addition, the first Neuropteran to have AFPs was identified, the lacewing Hemerobius simulans together with the second and third Diptera (the first Tipulids) and the second and third Hemiptera, the stinkbug Elasmostethus interstinctus (the first Pentatomid), and the water strider Limnoporus dissortis (the first Gerrid). Prior to this study, 33 species of insects and three spiders had been reported to have AFPs. Most AFP-producing terrestrial arthropods are freeze avoiding, and the AFPs function to prevent freezing. However, some of the AFP- producing insects identified in this study are known to be freeze tolerant (able to survive freezing) to very low temperatures (-40 to -70 degrees C).

Acclimatization↗
PubMed2006

Dynamic optimization over infinite-time horizon: web-building strategy in an orb-weaving spider as a case study.

Dynamic state-dependent models have been widely developed since 1990s for solving questions in evolutionary ecology. Up to now, these models were mainly run over finite-time horizon. However, for many biological questions an infinite-time horizon perspective could be more appropriate, especially when the end of the modeled period is state- rather than time-dependent. Despite this approach is widely used in the field of economics and operational research, thus far no work has been providing biologists with a general method to solve infinite-time horizon problems. Here we present such a method, through the exhaustive description of an algorithm that we implement to determine the strategy an organism should follow to reach a particular state as fast as possible while limiting mortality risk. To illustrate that method we explored web-building behavior in an orb-weaving spider. How are adult females predicted to build their successive webs to gain energy, grow, and lay their first clutch as fast as possible, without suffering from either predation or starvation? From this example, we first show how an optimal strategy over infinite-time horizon can be processed and selected. Second, we analyse variations of the optimal web-building strategy along with the spider's body weight and predation risk during web building. Our model yields two main predictions: (1) spiders reduce their web size as they are gaining weight due to body-mass-dependent cost of web-building behavior, and (2) this reduction in web size starts at lower weight under higher predation risk.

Algorithms↗
PubMed2005

Brain activation of spider phobics towards disorder-relevant, generally disgust- and fear-inducing pictures.

The present functional magnetic resonance imaging study investigated the fear and disgust reactivity of patients suffering from spider phobia. Ten phobics and 13 control subjects were scanned while viewing alternating blocks of phobia-relevant, generally fear-inducing, disgust-inducing and affectively neutral pictures. The patient group rated the spider pictures as being more disgust and fear evoking than the control group, and showed greater activation of the visual association cortex, the amygdalae, the right dorsolateral prefrontal cortex and the right hippocampus. Specific phobia-related activation occurred in the supplementary motor area. The patients also showed greater amygdala activation during the presentation of generally disgust- and fear-inducing pictures. This points to an elevated sensitivity to repulsive and threatening stimuli in spider phobics and implicates the amygdala as a crucial neural substrate.

Adult↗
PubMed2006

Effects of dimethoate on spiders from metal pollution gradient.

In this study, an attempt has been made to assess whether a chronic exposure to metals in habitats under a strong industrial pressure might have equipped spiders with biochemical defensive mechanisms enabling them to survive an additional chemical stress. To check this, non-web-building wolf spiders Pardosa lugubris (Lycosidae) and funnel web Agelena labyrinthica (Agelenidae) were collected at five variously polluted meadows and, under laboratory conditions, intoxicated with either single or multiple dose of dimethoate (OP pesticide). Then the activities of detoxifying (carboxylesterase: CarE, glutathione S-transferase: GST), antioxidative (selene-dependent and selene-independent glutathione peroxidases: GPOX and GSTPx) enzymes as well as acetylcholinesterase as a biomarker of exposure to OP pesticides were measured. In web-building A. labyrinthica, even a single application of the pesticide caused the inhibition of CarE, GSTPx and GPOX in individuals from less polluted sites and AChE and GST in specimens pre-exposed to high metal concentrations. Multiple intoxication, irrespectively of the site, caused significant, in comparison to controls, decrease in CarE, AChE and GSTPx activities. Actively hunting P. lugubris seem more resistant to acute pesticide intoxication, since the spiders from each site had a constant level of GST and AChE. In individuals of this species from heavily polluted sites, the inhibition caused by multiple intoxication with dimethoate was stated only for glutathione peroxidases.

Acetylcholinesterase↗