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Recent reports have suggested the use of dapsone for brown spider bites. This drug, for many years restricted to use in cases of leprosy and rare dermatologic disorders, has significant side effects that must be recognized. A case of methemoglobinemia is reported in one such patient treated with dapsone. The difficulty of making the diagnosis of brown spider bite is discussed.
The brown recluse spider (Loxosceles reclusa), found in many areas of the United States, is capable of producing significant medical problems and potentially life-threatening systemic manifestations. This paper reviews the clinical presentation, diagnostic workup, pathophysiology, and management of the brown spider bite. Emphasis is placed on the potential for error in establishing this diagnosis. The need for a simplified management program is discussed along with current concepts on how to achieve this management program. Attention is also directed to the more serious complications.
1. Raw venoms from a number of Australian Araneomorph spiders were found to cause epidermal disruption in cultured skin from both mice and humans. 2. The more potent ones also caused loss of epidermal cell-cell adhesion of mouse skin in vivo. 3. Raw venoms from three Mygalomorph species did not have these actions. 4. Venom gland extracts from the Araneomorph species were also ineffective. 5. It was concluded that where spider venoms appear to possess necrogenic activity the most likely reason for this is contamination of the venoms with digestive tract secretions.
1. Venom samples from twelve different Australian spider species were compared for their toxic effects on the heart and respiratory systems of anaesthetized rats. 2. The first and most serious effect of all venoms was on breathing, cardiotoxicity mostly being secondary to respiratory failure. 3. Only Atrax infensus and Selenocosmia stirlingi venoms proved highly toxic to rats, and therefore potentially toxic to humans, when single doses were used. 4. The low potency of most of the other venoms tested showed that several simultaneous spider bites would be necessary to cause significant toxicity.
Toxins from spider venom, originally purified for their ability to block synaptic transmission in Drosophila, are potent and specific blockers of Ca2+ currents measured in cultured embryonic Drosophila neurons using the whole-cell, patch-clamp technique. Differential actions of toxins from two species of spiders indicate that different types of Drosophila neuronal Ca2+ currents can be pharmacologically distinguished. Hololena toxin preferentially blocks a non-inactivating component of the current, whereas Plectreurys toxin blocks both inactivating and non-inactivating components. These results suggest that block of a non-inactivating Ca2+ current is sufficient to block neurotransmitter release at Drosophila neuromuscular junction.
We examined the effect of argiopine and argiopinine 3, low molecular weight polyamine venom components of the spider Argiope lobata, on rat cortical excitatory amino acid (EAA) receptors expressed in Xenopus oocytes. Responses to 100 microM N-methyl-D-aspartate (NMDA) with 10 microM glycine were blocked by both of the polyamine toxins in a dose-dependent manner. Both compounds had similar potencies against 100 microM kainate or 50 microM (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (L-AMPA). Oscillatory responses to 2 microM quisqualate were unaffected by either polyamine toxin. Increasing concentrations of either NMDA, kainate or AMPA were unable to overcome the antagonism by either spider toxin. We were able to demonstrate a use-dependent phenomenon similar to that of phencyclidine; neither polyamine toxin affected the NMDA, kainate or AMPA response without the presence of the respective agonist.
Simple heuristics may help explain how even a spider, despite its minute brain, can be disturbingly intelligent. Hutchinson and Gigerenzer suggest that the generalist-specialist distinction (or more accurately the predictability-unpredictability distinction) may be related to a species' level of reliance on simple heuristics, and spider behaviour may present some especially instructive opportunities for investigating these ideas. Daniel Dennett's distinction between Darwinian, Skinnerian and Popperian animals might be useful for discerning the different contexts in which optimality considerations and individual decision making are relevant.
Various spider species produce dragline silks with different mechanical properties. The primary structure of silk proteins is thought to contribute to the elasticity and strength of the fibres. Previously published work has demonstrated that the dragline silk of Euprosthenops sp. is stiffer then comparable silk of Nephila edulis, Araneus diadematus and Latrodectus mactans. Our studies of Euprosthenops dragline silk at the molecular level have revealed that nursery web spider fibroin has the highest polyalanine content among previously characterised silks and this is likely to contribute to the superior qualities of pisaurid dragline.
Spiders have highly developed mechanosensory systems, some of which provide access to forms of stimulation alien to our own sensations. Studies of hair-shaped air movement detectors (trichobothria) and tactile sensors have uncovered an outstanding refinement of the processes of stimulus uptake and stimulus transformation, which reflect details of both stimulus physics and behavioral significance. They also emphasize the potential contained in the seemingly simple Bauplan of arthropod cuticular hairs. Embedded into the spider exoskeleton are several thousands of strain detectors (slit sensilla) measuring compressive exoskeletal strains induced by various forms of loads and forces. A compound slit sensillum (lyriform organ) on the leg has become an important model system for studies of mechanoreceptor primary processes at the cellular and membrane level.
Construction of a safe refuge is the first step toward the evolution of social organization in spiders. In the case of the subsocial spider Amaurobius Jerox (Araneae, Amaurobiidae), the young remain in the natal nest after consuming their mother's body (matriphagy). The benefit that the young could obtain from the maternal web was investigated in their collective prey capture. The results demonstrated the adaptive value of the maternal web. The prey capturing activity was more effective when the young were allowed to stay on the maternal web than when they used the web constructed by themselves. Maternal web may also provide a better transmission of information on prey state and clutch mates' activities, because more spiderlings were recruited to contact and hold the prey in a shorter period of time than when they were on a spiderling-constructed web. The young's inheritance of the maternal nest is probably one of the crucial ways in which the mother influences the post-maternal social period of the young.
The present study reports the identification of immune related transcripts from hemocytes of the spider Acanthoscurria gomesiana by high throughput sequencing of expressed sequence tags (ESTs). To generate ESTs from hemocytes, two cDNA libraries were prepared: one by directional cloning (primary) and the other by the normalization of the first (normalized). A total of 7584 clones were sequenced and the identical ESTs were clustered, resulting in 3723 assembled sequences (AS). At least 20% of these sequences are putative novel genes. The automatic functional annotation of AS based on Gene Ontology revealed several abundant transcripts related to the following functional classes: hemocyanin, lectin, and structural constituents of ribosome and cytoskeleton. From this annotation, 73 transcripts possibly involved in immune response were also identified, suggesting the existence of several molecular processes not previously described for spiders, such as: pathogen recognition, coagulation, complement activation, cell adhesion and intracellular signaling pathway for the activation of cellular defenses.
Acute generalized exanthematous pustulosis (AGEP) is a rare severe cutaneous adverse reaction caused mostly by drugs. Three of 22 AGEP cases (13.6%), recruited by us as part of two prospective multinational studies, occurred 24 to 48 hours after a spider bite. We suggest that a spider bite is a possible trigger for AGEP.
Previous research [Hofmann SG, Meuret AE, Smits JA, Simon NM, Pollack MH, Eisenmenger K, et al. Augmentation of exposure therapy for social anxiety disorder with D-cycloserine. Archives of General Psychiatry 2006;63:298-304; Ressler KJ, Rothbaum BO, Tannenbaum L, Anderson P, Graap K, Zimand E, et al. Cognitive enhancers as adjuncts to psychotherapy: use of d-cycloserine in phobic individuals to facilitate extinction of fear. Archives of General Psychiatry 2004;61:1136-44] suggests that d-cycloserine (DCS) facilitates the reduction of clinical fear in humans. We used a well established intervention to evaluate the effectiveness of administering DCS as an adjunct to exposure therapy in a heightened, but sub-clinical, fear population. Over two studies, 100 spider-fearful participants were allocated to DCS or placebo before treatment and were assessed at pre-, immediate post-, and 3.5 weeks post-treatment. Significant treatment effects and return of fear was observed at follow-up, particularly in non-treatment contexts; however, both studies failed to demonstrate any enhancing effects of DCS (50 or 500 mg). DCS did not enhance the reduction of spider fears or the generalisation of treatment of a single session of exposure-based therapy. These results suggest that DCS may not enhance loss of non-clinical levels of fear in human populations.
Several spider neurotoxins are known to show highly selective effects on nervous tissues. Intracerebral injection into rats of spider venom from Scaptocosa raptoria, prevents seizures induced by convulsant agents. Injection of phenytoin (390 pmol/200 nl), muscimol (90 pmol/200 nl), baclofen (500 pmol/200 nl) into the substantia nigra (SN) pars reticulata, protected rats from convulsions evoked by unilateral focal injection of bicuculline into the area tempestas by 50, 80, and 100%, respectively. Denatured S. raptoria crude venom (4.6 microg, 2.3 microg, and 920 ng/200 nl), when administered into the SN, prevented seizures elicited by bicuculline in the area tempestas by 100, 100, and 87.5%, respectively. The injection into the SN of 160 ng/200 nl of fraction SrTx1 isolated from S. raptoria venom, reduced the magnitude of seizures. This fraction was rechromatographed affording fractions SrTx1.1, SrTx1.2 and SrTx1.3, and they were administered into the SN at doses of 100, 200, and 400 ng/200 nl respectively. Fraction SrTx1.3 protected 50, 85.7, and 100% of the animals against the seizures elicited by bicuculline injected into the area tempestas. This suggests that S. raptoria venom as well as its SrTx1.3 fraction, might be potential sources of new anticonvulsant drugs.
Linear free polyamines were characterized in the venom of the spiders Agelenopsis aperta, Hololena curta, and Paracoelotes birulai by RP-HPLC coupled to mass spectrometry. The several linear polyamines found were tetramine, pentamine, and hexamine derivatives. Some of these natural products were identified as N-hydroxylated, guanidylated, or acetylated compounds. In addition, the biosynthetical pathway leading to the formation of acylpolyamines in spider venoms is discussed.
Leg development in Drosophila has been studied in much detail. However, Drosophila limbs form in the larva as imaginal discs and not during embryogenesis as in most other arthropods. Here, we analyze appendage genes in the spider Cupiennius salei and the beetle Tribolium castaneum. Differences in decapentaplegic (dpp) expression suggest a different mode of distal morphogen signaling suitable for the specific geometry of growing limb buds. Also, expression of the proximal genes homothorax (hth) and extradenticle (exd) is significantly altered: in the spider, exd is restricted to the proximal leg and hth expression extends distally, while in insects, exd is expressed in the entire leg and hth is restricted to proximal parts. This reversal of spatial specificity demonstrates an evolutionary shift, which is nevertheless compatible with a conserved role of this gene pair as instructor of proximal fate. Different expression dynamics of dachshund and Distal-less point to modifications in the regulation of the leg gap gene system. We comment on the significance of this finding for attempts to homologize leg segments in different arthropod classes. Comparison of the expression profiles of H15 and optomotor-blind to the Drosophila patterns suggests modifications also in the dorsal-ventral patterning system of the legs. Together, our results suggest alterations in many components of the leg developmental system, namely proximal-distal and dorsal-ventral patterning, and leg segmentation. Thus, the leg developmental system exhibits a propensity to evolutionary change, which probably forms the basis for the impressive diversity of arthropod leg morphologies.
Hotspot archipelagoes provide exceptional models for the study of the evolutionary process, due to the effects of isolation and topographical diversity in inducing the formation of unique biotic assemblages. In this paper, we examine the evolutionary patterns exhibited by the jumping spider genus Havaika Prószyński, 2001 in the Polynesian islands of the Hawaiian and Marquesas chains. To date, systematic research on Havaika has been seriously limited by the poor taxonomic knowledge on the group, which was based on a handful of specimens that showed continuous variability and lacked clear-cut diagnostic characters. Here, we circumvent this problem by inferring a phylogeny based on DNA sequences of several fragments including both mitochondrial (protein coding cytochrome oxidase I, NAD1 dehydrogenase, ribosomal 16S, and tRNA leu) and nuclear (internal transcribed spacer 2) genes, and a statistical morphological analyses of a large sample of specimens. Results suggest that the Marquesan and Hawaiian Havaika may be the result of independent colonizations. Furthermore, data provide little support for the standard "progression rule" (evolution in the direction of older to younger islands) in Hawaiian Islands. This may be explained by a recent arrival of the group: age estimates of the different lineages suggest that Havaika colonized the Hawaiian Islands after most of the extant islands were already formed. The lack of clear-cut diagnostic characters among species may also be explained by the recent origin of the group since molecular data do not provide any evidence of hybridization among lineages. Quantitative morphological data coupled with the phylogenetic information allow us to reevaluate the current limitation of Havaika taxonomy. Molecular data support the existence of at least four different evolutionary lineages that are further morphologically diagnosable. However, genealogical relationships are better predicted by geographical affinity (i.e. island) than by morphological characters used in the original descriptions of the species. A pattern of size segregation linked to largely overlapping distributions of some of the species hints at a potential involvement of competition in generating morphological diversity. This study contributes to our understanding on the origin and shaping of the biodiversity of oceanic islands and sets the stage for more detailed studies on particular aspects of these previously overlooked spiders.
Orb-weaving spiders produce webs using two types of silk that have radically different mechanical properties. The dragline silk used to construct the supporting frame and radii of the web is stiff and as strong as steel, while the capture spiral is much weaker but more than ten times as extensible. This remarkable divergence in mechanical properties has been attributed to the aqueous glue that coats the capture spiral, which is thought to decrease capture spiral stiffness and increase its extensibility. However, discerning the effect of the aqueous glue on fiber performance is complicated because dragline silk and the capture spiral are assembled from different proteins, which may also affect mechanical performance. Here, we use the sticky gumfooted lines of black widow cobwebs to test the effect of the addition of aqueous glue on the mechanical properties of dragline silk. We also surveyed orb-webs spun by a broad range of species for bundles of looped silk. Such bundles, termed windlasses, have been thought to increase capture spiral extensibility by "paying out" additional lengths of silk. Our results suggest that neither plasticization of silk by aqueous glue nor excess silk in windlasses can by themselves account for the remarkable extensibility of orb-weaver capture silk compared to other spider silks. This argues that the unique amino acid motifs of the flagelliform fibroins that constitute the core of the capture spiral play an essential role in capture silk's extreme extensibility.