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 415 records · Page 23Linked to original sources
PubMed1997

The predatory response of a stalking spider, Plexippus paykulli, to camouflage and prey type

When approaching prey, a stalking predator should consider trade-offs between the probabilities of early detection (by the prey, before the strike), spontaneous departure (of prey, before the strike), prey escape (following the strike) and interference (by rivals or predators). In this study we tested the response of a jumping spider, Plexippus paykullito a background with two different camouflaging properties, and two different prey types (maggots versus adult house flies). Spiders jumped towards adult house flies from greater distances on a non-camouflaging background, but background colour had no effect on jumping distance when the prey were maggots. Spiders stalking both prey types approached more slowly when camouflaged. Our experiments suggest that jumping spiders may be responding to changes in the trade-off relationships between the probabilities of early detection, spontaneous departure, escape and interference.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗
PubMed1998

Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region

Social spiders are typically found only in the tropics. In laboratory tests and field observations, adult female A. studiosus in two populations in Tennessee, U.S.A., a temperate region, showed inter-attraction (grouping behaviour caused by the presence of conspecifics), greater tolerance towards conspecifics, and cooperation during prey capture and brood care. These are the three classical conditions considered typical of social spiders. The populations also had female-biased sex ratios and limited dispersal. Anelosimus studiosus can thus be regarded as a quasi-social or cooperative spider species. These populations of A. studiosus are the first social spiders to be described from typically temperate regions. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Asymmetry in spider orb webs: a result of physical constraints?

A typical feature of most vertical orb webs is that the upper web region is smaller and contains less silk than the lower web region, creating an asymmetrical web. The degree of web asymmetry changes during the spider's development: small juveniles construct more symmetrical webs, but older and larger individuals decrease the upper web region. This implies that weight may control the extent of web asymmetry. Using two species, Argiope keyserlingi and Larinioides sclopetarius, we tested the effect of weight increase on web asymmetry by naturally increasing weight through feeding and by artificially adding lead weights to the abdomen of the spiders. Weight increase (natural or artificial) resulted in more asymmetric webs through a reduction of the upper web region. Added weight may interfere with spiral placement in the upper region, because the spider has to lift its abdomen above the carapace during the process. In the lower region, however, the position of the spider is mostly head up during spiral placement. Therefore, amongst other factors, weight and gravitational forces may be physical constraints during web construction. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2006

Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments.

The pycnogonids (or sea spiders) are an enigmatic group of arthropods, classified in recent phylogenies as a sister-group of either euchelicerates (horseshoe crabs and arachnids), or all other extant arthropods. Because of their bizarre morpho-anatomy, homologies with other arthropod taxa have been difficult to assess. We review the main morphology-based hypotheses of correspondence between anterior segments of pycnogonids, arachnids and mandibulates. In an attempt to provide new relevant data to these controversial issues, we performed a PCR survey of Hox genes in two pycnogonid species, Endeis spinosa and Nymphon gracile, from which we could recover nine and six Hox genes, respectively. Phylogenetic analyses allowed to identify their orthology relationships. The Deformed gene from E. spinosa and the abdominal-A gene from N. gracile exhibit unusual sequence divergence in their homeodomains, which, in the latter case, may be correlated with the extreme reduction of the posterior region in pycnogonids. Expression patterns of two Hox genes (labial and Deformed) in the E. spinosa protonymphon larva are discussed. The anterior boundaries of their expression domains favour homology between sea spider chelifores, euchelicerates chelicerae and mandibulate (first) antennae, in contradistinction with previously proposed alternative schemes such as the protocerebral identity of sea spider chelifores or the absence of a deutocerebrum in chelicerates. In addition, while anatomical and embryological evidences suggest the possibility that the ovigers of sea spiders could be a duplicated pair of pedipalps, the Hox data support them as modified anterior walking legs, consistent with the classical views.

Animals↗
PubMed2006

SPIRE: the SPIDER reconstruction engine.

SPIRE is a Python program written to modernize the user interaction with SPIDER, the image processing system for electron microscopical reconstruction projects. SPIRE provides a graphical user interface (GUI) to SPIDER for executing batch files of SPIDER commands. It also lets users quickly view the status of a project by showing the last batch files that were run, as well as the data files that were generated. SPIRE handles the flexibility of the SPIDER programming environment through configuration files: XML-tagged documents that describe the batch files, directory trees, and presentation of the GUI for a given type of reconstruction project. It also provides the capability to connect to a laboratory database, for downloading parameters required by batch files at the start of a project, and uploading reconstruction results at the end of a project.

Computational Biology↗
PubMed2000

UCS expectancy biases in spider phobics: underestimation of aversive consequences following fear-irrelevant stimuli.

This paper reports the results of two studies investigating judgements made by spider phobics about the potential threatening consequences (unconditioned stimulus, UCS, expectancies) associated with their phobic stimulus, fear-relevant (FR) stimuli, and fear-irrelevant (FI) stimuli. Using a 'thought experiment' UCS expectancy paradigm, the studies reported found that (1) spider phobics reported significantly higher UCS expectancies to spider stimuli than nonphobics, (2) spider phobics consistently underestimated the probability of aversive consequences following FI stimuli and (3) this underestimation of UCS expectancies to FI stimuli in phobics was not the result of a contrast effect resulting from sequential FR and FI judgements. This differential effect may have important implications for the kind of mechanism which mediates judgements about phobic consequences. These findings suggest that the dimensions on which phobic stimuli are categorised may be 'stretched' in the case of phobics and that this gives rise to the comparative underestimation of threat associated with FI stimuli but also makes phobics more vulnerable to acquiring other phobias.

Adolescent↗
PubMed2002

The toxin Tx4(6-1) from the spider Phoneutria nigriventer slows down Na(+) current inactivation in insect CNS via binding to receptor site 3.

Tx4(6-1) a neurotoxic peptide from the venom of the aggressive South American 'armed' spider Phoneutria nigriventer, has been previously isolated and sequenced. It shows no detectable activity in mice but affects the peripheral nervous system of insects by stimulating glutamate release at the neuromuscular junction. Here we investigate possible interactions of the toxin with voltage-activated sodium channels (Na(v)). We confirm that it is ineffective on mammalian Na(v) channels, and establish that it competes with the alpha-like toxin 125I-Bom IV, for binding on the site 3 of insect Na(v) channel (IC(50) value around 25nM). The physiological consequences of this binding to the insect Na(v) channel are shown by electrophysiology: Tx4(6-1) prolongs evoked axonal action potentials (APs) (<500&mgr;s duration in control). Prolonged 8-10ms or 'plateau' 500-800ms APs accompanied by repetitive firing at 80-150Hz are recorded after 4-8min of toxin action. This modification of evoked activity is due to a slowing down of sodium current inactivation. Effects of Tx4(6-1) on sodium current are compared with those of a typical scorpion alpha-toxin and of some other spider toxins active on insect Na(v) channels. At the end of long voltage pulses, the maintained inward sodium current may represent 50% of the peak current after scorpion alpha-toxin but only about 8-10% after spider toxins. To understand the slight differences in the effects of alpha-scorpion and spider toxins on the insect Na(v) channel, structural studies of toxin-channels interactions would be necessary.

Journal Article↗
PubMed2001

Long-duration whirling of Pholcus phalangioides (Araneae, Pholcidae) is specifically elicited by Salticid spiders.

Long-duration whirling (gyrating of the body during several hours a day) was shown by the pholcid spider Pholcus phalangioides to salticid spiders and hardly ever to predatory spiders from eight other families in laboratory arenas. Long-duration whirling has not been reported so far, in contrast to short-duration whirling lasting less than a few minutes. Long-duration whirling may have the anti-predatory function of disturbing continual visual fixation of prey in attacking salticids, in contrast to short-duration whirling that has been demonstrated to favour survival of pholcids in the presence of all sorts of predatory spiders.

Journal Article↗
PubMed2000

Spider mites of Japan: their biology and control.

Spider mite biology and control in Japan were reviewed. Seventy-eight spider mite species of 16 genera (Family Tetranychidae) have been recorded in Japan. Several of the species recently described were separated from a species complex comprising strains with different ecological performance such as host range. These separations were first supported by crossing experiments and then confirmed by molecular genetic studies. Spider mite control in Japan is still dependent on heavy acaricide spraying in order to attain products of extremely high quality. The commercial use of natural enemies in spider mite management has just started.

Animals↗
PubMed1997

Mapping chromosomal homology between humans and the black-handed spider monkey by fluorescence in situ hybridization.

We hybridized human chromosome-specific DNA probes to metaphases of the New World monkey Ateles geoffroyi to map the chromosomal homology between these two species. In the haploid Ateles geoffroyi karyotype the total number of signals was 51 for the 22 human autosomal probes used. Compared with Old World monkeys, the number of translocations found in the black-handed spider monkey karyotype was quite striking. The majority of these translocations are apparently Robertsonian and no reciprocal translocations were revealed. Nine autosomal human chromosome probes (11, 13, 14, 17, 18, 19, 20, 21, 22) provided only two signals each per metaphase, but six of these were translocated to subregions of different spider monkey chromosomes. The other 13 autosomal human chromosome paints (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 16) provided fragmented signals. Three human probes (5, 8, 10) provided signals located on two pairs of spider monkey chromosomes. Four human paints (2, 3, 4, 12) provided hybridization signals on three pairs of chromosomes. Probes 6, 7, 15 provided six signals each on two pairs of chromosomes; probe 16 gave eight signals on two pairs of spider monkey chromosomes and probe 1 gave 12 signals on four pairs of chromosomes. The synteny between segments to human 18/8 appears to be an apomorphic ancestral condition for all New World monkeys. A synteny between regions homologous to human 16/10, 5/7 and 2/16 HSA is probably an apomorphic ancestral condition for all Cebidae. The syntenic association 3/15 and 4/1 is an apomorphic condition for the Atelinae.

Animals↗
PubMed2003

Wolbachia distribution and cytoplasmic incompatibility based on a survey of 42 spider mite species (Acari: Tetranychidae) in Japan.

Wolbachia are a group of maternally inherited bacteria that infect a wide range of arthropods. Wolbachia infections are known to result in the expression of various abnormal reproductive phenotypes, the best known being cytoplasmic incompatibility. The first systematic survey of 42 spider mite species in Japan revealed that seven species (16.7%) were infected with Wolbachia. Wolbachia in the spider mites were grouped into three subgroups in supergroup B by phylogenetic analyses of the wsp gene. Most spider mites did not show cytoplasmic incompatibility when infected males were crossed with uninfected females. However, all infected populations of Panonychus mori and Oligonychus gotohi (five and four populations, respectively) possessed modification-positive strains of Wolbachia, and the cytoplasmic incompatibility decreased egg hatchability and female ratio of the spider mites. Thus, some Wolbachia strains cause sex ratio distortion in their hosts.

Animals↗
PubMed2006

Cardinium symbionts cause cytoplasmic incompatibility in spider mites.

Intracellular symbiotic bacteria belonging to the Cytophaga-Flavobacterium-Bacteroides lineage have recently been described and are widely distributed in arthropod species. The newly discovered bacteria, named Cardinium sp, cause the expression of various reproductive alterations in their arthropod hosts, including cytoplasmic incompatibility (CI), induction of parthenogenesis and feminization of genetic males. We detected 16S ribosomal DNA sequences similar to those of Cardinium from seven populations of five spider mite species, suggesting a broad distribution of infection of Cardinium in spider mites. To clarify the effect of Cardinium on the reproductive traits of the infected spider mites, infected mites were crossed with uninfected mites for each population. In one of the populations, Eotetranychus suginamensis, CI was induced when infected males were crossed with uninfected females. The other six populations of four species showed no reproductive abnormalities in the F(1) generation, but the possibility of CI effects in the F(2) generation remains to be tested. One species of spider mite, Tetranychus pueraricola, harbored both Cardinium and Wolbachia, but these symbionts seemed to have no effect on the reproduction of the host, even when the host was infected independently with each symbiont.

Animals↗
PubMed1999

Successful treatment of spider leg veins with a high-energy, long-pulse, frequency-doubled neodymium:YAG laser (HELP-G)

BACKGROUND: While sclerotherapy has been the standard treatment for spider leg veins for many years, recent advances have allowed lasers to be considered as a treatment option. OBJECTIVE: To study the efficacy of a frequency-doubled Nd:YAG laser at 532 nm with a 50 ms pulse width and chill tip device in the treatment of spider leg veins. METHODS: Forty-six patients with spider leg veins with a diameter of less than 1 mm or 1-2 mm were treated with a frequency-doubled Nd:YAG laser at 532 nm with a pulse width of 50 ms (VersaPulse HELP-G laser) while using a water-cooled chill tip device. RESULTS: Of patients with veins less than 1 mm in diameter, 60% had greater than 50% clearing after one treatment and 80% had greater than 50% clearing after two treatments. Of patients with veins 1-2 mm in diameter, 39% achieved greater than 50% clearing after one treatment and 67% had greater than 50% clearing after two sessions. CONCLUSION: Our results suggest that the frequency-doubled Nd:YAG laser with a pulse width of 50 ms and chill tip device offers an excellent alternative to sclerotherapy in the treatment of small spider leg veins.

Adult↗
PubMed1976

Ploy and counterploy in predator-prey interactions: Orb-weaving spiders versus bombardier beetles.

Bombardier beetles (Brachinus spp.) offered to orb-weaving spiders are either captured or lost, depending on the attack strategy of the spider. Nephila clavipes grasps a beetle directly and attempts to bite it outright, but is repelled by the beetle's defensive spray. As the spider recovers from the spray, the beetle makes its escape from the web. Argiope first imprisons the beetle by wrapping it delicately in silk, without causing it to spray. When the spider then proceeds to bite, the wrapping protects it against the full effects of the spray. The wrapping strategy may be generally effective against chemically protected insects, and it is suggested that this may be one of its principal adaptive justifications.

Journal Article↗
PubMed2006

Natural products: repellency and toxicity of wild tomato leaf extracts to the two-spotted spider mite, Tetranychus urticae Koch.

The potential of using phytochemicals from leaves of wild tomato for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study as a promising alternative to the use of synthetic pesticides. Wild tomato accessions of Lycopersicon hirsutum plants that are not consumed by humans were planted under greenhouse conditions for mass production of leaves. Crude extracts from leaves of three accessions of L. hirsutum, six accessions of L. hirsutum f. glabratum, and one accession each of L. pennellii and L. pimpinellifolium were prepared in chloroform, ethanol and hexane. Two spider mite bioassays, one a measure of antibiosis and the other a measure of repellency, were utilized to determine the acaricidal performance of the crude extracts. The bioassay for antibiosis was a 6-h no-choice test. The bioassay for repellency utilized a ring bioassay. Chloroform leaf extracts of L. hirsutum f. glabratum accessions (PI-251304, PI-134417, PI-134418, and PI-126449) exhibited greatest antibiotic activity on two-spotted spider mites; the hexane extracts exhibited greatest repellency. Extracts from PI-251304, PI-126449, PI-134417, and PI-134418 were especially lethal (chloroform) or repellent (hexane). We investigated differences in chemical composition of the crude leaf extracts that may explain the observed differences in mortality and repellency among the different accessions. Major chemical compounds (alpha -curcumene, alpha -zingiberene, trans-caryophyllene, 2-undecanone, and 2-tridecanone) known to have pesticidal efficacy were detected and quantified in the crude leaf extracts using a gas chromatograph (GC) equipped with a mass spectrometer (GC/MS). Lethality of extracts was mainly associated with the presence of high concentrations of 2-tridecanone; repellency of extracts was mainly associated with the presence of trans-caryophyllene. Leaf extracts of L. hirsutum f. glabratum accessions that contain significant quantities of 2-tridecanone and/or trans-caryophyllene could be useful for managing populations of spider mites, which could reduce reliance on synthetic pesticides.

Animals↗
PubMed2003

Response of spider leg veins to pulsed diode laser (810 nm): a clinical, histological and remission spectroscopy study.

BACKGROUND: Spider leg veins are common. Their treatment with laser or intensed light therapy shows generally variable success rates and often adverse side effects such as hyper- or hypopigmentation. This study was performed to investigate whether pulsed diode laser (810 nm) treatment is effective and safe. METHODS: Thirty-five female patients with spider leg veins were included in this prospective trial. They were treated twice with a pulsed diode laser (810 nm; spot size 12 mm, frequency 2-4 Hz, pulse width 60 msec, fluence 80-100 Jcm(-2)). Laser therapy was performed on day 0 and day 14. Clinical assessments were carried out before and immediately after the first laser therapy, after 2 weeks, 8 weeks, and one year. Skin biopsies were taken before and immediately after the first laser treatment, and after 10 weeks. Contact-free remittance spectroscopy was performed before laser treatment, immediately after the first treatment, after 2 weeks and 8 weeks. RESULTS: After the first treatment 15 patients showed a complete disappearance (CR) of spider leg veins; in the remaining 20 patients a remarkable improvement (RI) was noted (n=35). After six months of follow-up CR was seen in 6 patients, RI in 6, a stable situation in 9, and scar formation in 1 patient (n=21). The effect was almost completely stable during one year of follow-up. The examination of histological specimens before and after laser treatment showed no cellular inflammatory reaction. The mean vascular area was significantly reduced after the first (p<0.05) and after the second (p<0.05) laser treatment. Spectral analysis showed a marked decrease of peaks for oxygenized haemoglobin immediately after laser treatment and during the follow-up. Safety profile was excellent without purpuric reaction or pigmentary changes. Mild scarring was observed in two patients at the end of follow-up. CONCLUSIONS: Pulsed diode laser therapy (810 nm) is an effective and safe treatment option for spider leg veins. The effects can be seen immediately. Objective monitoring by non-invasive remission spectroscopy and histology of biopsy specimens demonstrates selectivity of the laser action.

Adult↗
PubMed2005

Genetic transfer of a twospotted spider mite (Acari: Tetranychidae) repellent in tomato hybrids.

Lycopersicon hirsutum Dunal is very resistant to arthropod herbivory, and research on causes of resistance has often implicated trichomes and their secretions. To better understand relationships among resistance, repellency, and 2,3-dihydrofarnesoic acid, a trichome-borne sesquiterpenoid spider mite repellent, two tomato, Lycopersicon esculentum Miller, varieties were interbred with a highly resistant, spider mite repellent accession (LA1363) of L. hirsutum. Backcross and F2 generations were produced with each tomato variety. Whole leaves of 99 hybrids were bioassayed with twospotted spider mites, Tetranychus urticae Koch, allowing selection of six hybrids (two susceptible and four resistant) for each generation of each family. When these 24 hybrids were characterized for spider mite repellency with thumbtack bioassays, two hybrids had repellent leaflets, demonstrating that repellency was genetically transferred to interspecific tomato hybrids. Leaflet washes containing trichome secretions from each of three hybrids, including the two having repellent leaflets, were repellent in bridge bioassays. For the two hybrids having repellent leaflets and leaflet washes, removal of trichome secretions by dipping leaflets in methanol eliminated leaflet repellency. 2,3-Dihydrofarnesoic acid was present in trichome secretions of the hybrids having leaflet repellency, and it also was present in secretions of other hybrids, indicating that its presence is essential, but not sufficient for leaflet repellency. With regard to resistance, 16 of the hybrids tested had been identified as resistant in a whole leaf bioassay, but only two had repellent leaflets, indicating that other mechanisms of resistance are present in the resistant L. hirsutum parent.

Animals↗
PubMed1994

Detoxification of Formaldehyde by the Spider Plant (Chlorophytum comosum L.) and by Soybean (Glycine max L.) Cell-Suspension Cultures.

The phytotoxicity of formaldehyde for spider plants (Chlorophytum comosum L.), tobacco plants (Nicotiana tabacum L. cv Bel B and Bel W3), and soybean (Glycine max L.) cell-suspension cultures was found to be low enough to allow metabolic studies. Spider plant shoots were exposed to 7.1 [mu]L L-1 (8.5 mg m-3) gaseous [14C]-formaldehyde over 24 h. Approximately 88% of the recovered radioactivity was plant associated and was found to be incorporated into organic acids, amino acids, free sugars, and lipids as well as cell-wall components. Similar results were obtained upon feeding [14C]formaldehyde from aqueous solution to aseptic soybean cell-suspension cultures. Serine and phosphatidylcholine were identified as major metabolic products. Spider plant enzyme extracts contained two NAS+-dependent formaldehyde dehydrogenase activities with molecular mass values of about 129 and 79 kD. Only the latter enzyme activity required glutathione as an obligatory second cofactor. It had an apparent Km value of 30 [mu]M for formaldehyde and an isoelectric point at pH 5.4. Total cell-free dehydrogenase activity corresponded to 13 [mu]g formaldehyde oxidized h-1 g-1 leaf fresh weight. Glutathione-dependent formaldehyde dehydrogenases were also isolated from shoots and leaves of Equisetum telmateia and from cell-suspension cultures of wheat (Triticum aestivum L.) and maize (Zea mays L.). The results obtained are consistent with the concept of indoor air decontamination with common room plants such as the spider plant. Formaldehyde appears to be efficiently detoxified by oxidation and subsequent C1 metabolism.

Journal Article↗