Plant glandular trichomes mediate protective mutualism in a spider-plant system

1. Although several species of Peucetia (Oxyopidae) live strictly in association with plants bearing glandular trichomes worldwide, to date little is known about whether these associations are mutualistic.2. In this study we manipulated the presence of Peucetia flava on the glandular plant Rhynchanthera dichotoma in the rainy and post-rain season, to test the strength of its effects on leaf, bud, and flower damage and plant reproductive output. In addition, we ran independent field experiments to examine whether these sticky structures improve spider fidelity to plants.3. Peucetia suppressed some species of foliar phytophages, but not others. Although spiders have reduced levels of leaf herbivory, this phenomenon was temporally conditional, i.e. occurred only in the post-rain but not in the rainy season. Floral herbivory was also reduced in the presence of spiders, but these predators did not affect plant fitness components.4. Plants that had their glandular trichomes removed retained fewer insects than those bearing such structures. Spiders remained longer on plants with glandular trichomes than on plants in which these structures had been removed. Isotopic analyses showed that spiders that fed on live and dead labelled flies adhered to the glandular hairs in similar proportions.5. Spiders incurred no costs to the plants, but can potentially increase individual plant fitness by reducing damage to reproductive tissues. Temporal conditionality probably occurred because plant productivity exceeded herbivore consumption, thus dampening top-down effects. Specialisation to live on glandular plants may have favoured scavenging behaviour in Peucetia, possibly an adaptation to periods of food scarcity.

Spider assemblages in widely-separated patches of cerrado in São Paulo State, Brazil.

Brazilian cerrado is a biologically-rich, poorly understood, yet rapidly disappearing habitat. Composition of the spider assemblages from areas of cerrado from three separate sites in the State of São Paulo, Brazil were sampled by beating the canopies and adjacent shrubs of three Myrcia (Myrtaceae; "myrtle") tree species. These produced a total of 859 spiders 'belonging to 21 families and 75 species. The most undisturbed and densest cerrado habitat had the largest number and greatest diversity of spider species, encompassing stalkers, ambushers, space web-weavers, and foliage runners. The other two areas were dominated by foliage runners. Spider distribution in this natural and complex habitat was evaluated by classifying the samples into 12 habitat/microhabitat groups according to local of the patch, tree species, and microhabitat (target tree or adjacent shrub). Correspondence analysis was used for ordination of species and groups based on their abundance. Environmental factors such as patches type (p=0.027) and plant species (p=0.046) had significant effects in explaining the ordination. Canonical correspondence analysis was applied for relating the patterns in species richness and/or abundance to the significant environmental factors. A comparison of the results showed that the family composition among the patches is rather similar, and there is a tendency of spiders species overlap an interregional level (patches effect, p=0.027). However, the most similar spider assemblages living on woody vegetation occurred in Myrcia venulosa and Myrcia guianensis at São Carlos and Pirassununga, demonstrating an interregional similarity (plant species effect, p=0.046) that indicates an association between spiders and particular vegetation.

Communication and synchronized molting in a colonial araneid spider, Eriophora bistriata

The colonial orb-weaving spider, Eriophora bistriata, coordinates molting cycles through communication. Colonies with differing molting cycles synchronize when combined. Intercycle intervals depend upon food availability. The possible coordination of this synchrony by chemical communication among spiders is discussed. © 1988 Birkhäuser Verlag Basel.

Interference competition and scavenging by Crematogaster ants (Hymenoptera: Formicidae) associated with the webs of the social spider Anelosimus eximius (Araneae: Theridiidae) in the central Amazon

Crematogaster cf. victima is a common inhabitant in the sheet web nests of the social spider Anelosimus eximius in the central Amazon basin near Manaus. A number of other ant species were found foraging on the non-sticky webs of A. eximius, but none of these reached the web occupation frequency found in C. cf. victima, nor, with the exception of an unidentified species of Pheidole, did they form satellite nests in the web, as did this species. Many prey which escaped the knock-down threads of the sheet web of A. eximius colonies were captured by ants in the lower web portions which they dominated. Furthermore, prey which were rejected by A. eximius, especially large, heavily sclerotized beetles, were also consumed by this ant. Repeated observations and experiments suggest that C. cf. victima is able to deter A. eximius activity through aerial venom release. Resources lost by A. eximius colonies to ants, especially C. cf. victima, in colonial web area and prey, may pose significant costs and may reduce colony growth.

Bathymetric distribution and recruitment of the spider crab Libinia spinosa H. Milne Edwards 1834 in the Ubatuba and Caraguatatuba regions, northern coast of São Paulo, Brazil (Crustacea, Brachyura, Majoidea, Pisidae)

The objective of this study was to investigate the spatial and temporal distribution of Libinia spinosa H. MILNE EDWARDS 1834 on unconsolidated sublittoral bottoms in two regions off the northern coast of the state of São Paulo, and to analyze the influence of environmental factors on the occurrence of this species and observe the recruitment pattern of its young. Crabs were collected monthly (July 2001 through June 2003) at depths of 5, 10, 15, 20, 25, 30 and 35 In, from a fishing boat equipped with two double-rig nets. Samples of water and sediment were collected for analysis of environmental factors. A total of 2112 spider crabs was obtained (701 juveniles and 1411 adults). The highest abundance was observed at depths of 20 and 25 m, in both regions. These localities were characterized by substrate composed of very fine sand and silt-clay. In regard to the temporal distribution, juveniles and adults predominated in the summer and winter months respectively. From these results, one can infer that the distribution of L. spinosa is related to environmental factors favorable for its life cycle; sediment type is the factor which most strongly determines its presence. © E. Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller), 2007.

The acylpolyamines from spider venoms

Acylpolyamines are low molecular mass toxins occurring exclusively in the venoms from solitary wasps and some groups of spiders. Their chemical structures have been elucidated using hyphenated techniques of mass spectrometry, such as LC-MS and MS/MS, or through direct analysis with different types of NMR analyses. The chemical structures of the acylpolyamine toxins from the venoms of Nephilinae orb-web spiders appear to be organized into four parts based on the combinatorial way that the chemical building blocks are bound to each other. An aromatic moiety (part I) is connected through a linker amino acid (part II) to a polyamine chain (part III), which in turn may be connected to an optional tail (part IV). The polyamine chains were classified into seven subtypes according to the different combinations of chemical building blocks. These polyamine chains, in turn, are connected to one of three chromophore moieties: a 2,4-dihydroxyphenyl acetyl group, a 4-hydroxyindolyl acetyl group, or an indolyl acetyl group. They may be connected through an asparagine residue or sometimes through the dipeptide ornithyl asparagine. Also, nine different types of backbone tails may be attached to the polyamine chains. These toxins are noncompetitive blockers of ionotropic glutamate receptors with neuroprotective action against the neuronal death and antiepileptic effect. Thus, compounds of this class of spider venom toxin seem to represent interesting molecular models for the development of novel neuropharmaceutical drugs. © 2012 Elsevier B.V. All rights reserved.

Phylogeny and taxonomic revision of the spider mite genera Aponychus, Paraponychus and Stylophoronychus using morphology (Acari:Tetranychidae)

Despite their great importance as pests of cultivated plants worldwide, members of the family Tetranychidae have never been subjected to a thorough cladistic analysis to reveal the history and relationships among related genera. Herein, we provide the first phylogenetic analysis and taxonomic review of species of the genera Aponychus, Paraponychus and Stylophoronychus using morphological characters. The results indicate a monophyletic clade uniting the aforementioned genera, although none of the three genera were recovered as monophyletic. We reinstate the tribe Aponychini as the taxon containing those three genera. Aponychus bambusae and A. aequilibris are herein considered junior synonyms of Stylophoronychus vannus and A. corpuzae, respectively. © 2013 CSIRO.

Chromosomal characteristics of a Brazilian whip spider (Amblypygi) and evolutionary relationships with other arachnid orders

We analyzed mitotic and meiotic cells of a Brazilian amblypygid, Heterophrynus longicornis, using conventional and molecular cytogenetic techniques (Giemsa staining, C-banding, Ag-NOR, and FISH with rDNA probe). This is the first study that focuses solely on amblypygid chromosomes; it was undertaken to add data on cytogenetic knowledge of this group and contribute to the understanding of chromosome evolution in the Arachnida. We found 2n = 66 for male and female individuals, monocentric chromosomes, and absence of morphologically differentiated sex chromosomes. C-banding showed heterochromatin in the pericentromeric region of most chromosomes. Mitotic and meiotic nuclei submitted to silver impregnation and FISH revealed, respectively, Ag-NORs and ribosomal genes in the terminal region of two chromosome pairs. Most chromosome features that we observed in H. longicornis are shared with species of other arachnid orders; however, the absence of morphologically differentiated sex chromosomes in amblypygid contrasts with the remarkable variety of sex chromosome systems recorded for the Araneae. Consequently, we conclude that analysis of species of the Tetrapulmonata clade is useful for understanding the trends of sex chromosome evolution in this arachnid group. © FUNPEC-RP.

The spider genera Euthycaelus Simon and Schismatothele Karsch (Mygalomorphae, Theraphosidae)

The genus Euthycaelus Simon 1889 is diagnosed based on the examination of type-material and additional material from Venezuela and Colombia. The genus now includes: Euthycaelus colonicus Simon 1889, E. norae sp. nov., E. amandae sp. nov.; Euthycaelus steini Simon 1889 is transferred to Psalistops comb. nov. The genus Schismatothele Karsch 1879 is considered a senior synonym of Hemiercus Simon 1903. Schismatothele includes S. lineata Karsch 1879, S. inflata (Simon 1889) comb. nov., S. modesta (Simon 1889) comb. nov, and S. benedettii Panzera et al. 2011. Hemiercus proximus Mello-Leitao 1923, from Cubatao, Sao Paulo, Brazil, is transferred to Acanthoscurria proxima (Mello-Leitao 1923) comb. nov. Hemiercus kastoni Caporiacco 1955 is considered a species inquirenda pending the examination of the type material.

A rare finding of mites (Arachnida: Acari: Leeuwenhoekiidae) parasitising a whip spider (Arachnida: Amblypygi: Charinidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Recent advances in the understanding of brown spider venoms: From the biology of spiders to the molecular mechanisms of toxins

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Disentangling the Phylogenetic and Ecological Components of Spider Phenotypic Variation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Social-spider optimization-based artificial neural networks training and its applications for Parkinson's disease identification

Evolutionary algorithms have been widely used for Artificial Neural Networks (ANN) training, being the idea to update the neurons' weights using social dynamics of living organisms in order to decrease the classification error. In this paper, we have introduced Social-Spider Optimization to improve the training phase of ANN with Multilayer perceptrons, and we validated the proposed approach in the context of Parkinson's Disease recognition. The experimental section has been carried out against with five other well-known meta-heuristics techniques, and it has shown SSO can be a suitable approach for ANN-MLP training step.

Two-spotted spider mite and its natural enemies on strawberry grown as protected and unprotected crops in Norway and Brazil

Cultivation of strawberry in plastic tunnels has increased considerably in Norway and in southeastern Brazil, mainly in an attempt to protect the crop from unsuitable climatic factors and some diseases as well as to allow growers to expand the traditional production season. It has been hypothesized that cultivation under tunnels could increase the incidence of one of its major pests in many countries where strawberry is cultivated, including Norway and Brazil, the two spotted spider mite, Tetranychus urticae. The objective of this study was to evaluate the effect of the use of tunnels on the incidence of T. urticae and on its natural enemies on strawberry in two ecologically contrasting regions, Norway (temperate) and southeastern Brazil (subtropical). In both countries, peak densities of T. urticae in tunnels and in the open fields were lower than economic thresholds reported in the literature. Factors determining that systematically seem to be the prevailing relatively low temperature in Norway and high relative humidity in both countries. The levels of occurrence in Norway and Brazil in 2010 were so low that regardless of any potential effect of the use of tunnel, no major differences were observed between the two cropping systems in relation to T. urticae densities. In 2009 in Norway and in 2011 in Brazil, increase in T. urticae population seemed to have been restrained mainly by rainfall in the open field and by predatory mites in the tunnels. Phytoseiids were the most numerous predatory mite group of natural occurrence on strawberry, and the prevalence was higher in Brazil, where the most abundant species on strawberry leaves were Neoseiulus anonymus and Phytoseiulus macropilis. In Norway, the most abundant naturally occurring phytoseiids on strawberry leaves were Typhlodromus (Anthoseius) rhenanus and Typhlodromus (Typhlodromus) pyri. Predatory mites were very rare in the litter samples collected in Norway. Infection rate of the pest by the fungus Neozygites floridana (Neozygitaceae) was low. The results of this work suggest that in Norway the use of tunnels might not affect the population densities of T. urticae on strawberry in years of lower temperatures. When temperature is not a limiting factor for the development of T. urticae in that country (apparently always the case in southern Brazil), strawberry cultivation in the tunnels may allow T. urticae to reach higher population levels than in open fields (because of the provided protection from the direct impact of rainfall), but natural enemies may prevent higher levels from being reached.

Structural insights into substrate binding of brown spider venom class II phospholipases D

Phospholipases D (PLDs), the major dermonecrotic factors from brown spider venoms, trigger a range of biological reactions both in vitro and in vivo. Despite their clinical relevance in loxoscelism, structural data is restricted to the apo-form of these enzymes, which has been instrumental in understanding the functional differences between the class I and II spider PLDs. The crystal structures of the native class II PLD from Loxosceles intermedia complexed with myo-inositol 1-phosphate and the inactive mutant H12A complexed with fatty acids indicate the existence of a strong ligand-dependent conformation change of the highly conserved aromatic residues, Tyr 223 and Trp225 indicating their roles in substrate binding. These results provided insights into the structural determinants for substrate recognition and binding by class II PLDs.