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In this study, Latrodectus revivensis Shulov, 1948 is recorded for the first time from Iran based on female specimens. This species was previously recorded from the eastern Mediterranean region. As a result, the number of Latrodectus species recorded from Iran is raised to six. A comparative diagnosis is provided for this species and other widow spiders previously recorded from the country. Latrodectus revivensis can be easily distinguished from its congeners by colouration, genitalic characters and the shape of the nest. This record represents the easternmost distribution limit of L. revivensis. An updated distribution map of Latrodectus species is also provided. [ABSTRACT FROM AUTHOR]

Objective: The Mediterranean black widow spider; Latrodectus tredecimguttatus (Rossi, 1790) could reasonably be regarded by many health practitioners as living solely in Southern Europe. However, its range extends well beyond the Mediterranean, into central Asia, and reaches parts of China. In this article, we detected this species in Jordan for the first time and confirmed the diagnosis by DNA barcoding. This is also the first clinically significant envenomation case in Jordan. Materials and Methods: The spider was identified using DNA analysis which was extracted using a Qiagen DNeasy Blood and Tissue Kit following the standard protocol. PCR reactions were conducted in 20 µL volumes using 1 µL of DNA template, a final concentration of 0.5 µM of each primer. Cycling conditions consisted of an initial activation at 95°C for 15 min, then 35 cycles of denaturation at 95°C for 30 s, annealing at 45°C for 30 s and elongation at 72°C for 1 min with a final elongation at 72°C for 10. Successful PCR reactions were cleaned using Clean NA Clean PCR magnetic beads (GC Biotech) using the standard PCR cleanup protocol. Bi-directional sequencing was conducted at Genewiz UK. Results: The species was identified using morphological and molecular data. The clinical process was evaluated including the symptoms, medical treatment, and the use of Ferula assa-foetida as self-medicated traditional medicine. Discussion: The first record of this spider is very important for the contribution of the biodiversity of Jordan. In addition, due to its medical importance, the envenomation case and its treatment with Freula are important for local practitioners. Such medically important animals and related cases need to be documented for public health. It is necessary to recognize the existence of venomous spiders in Jordan, and to study their patterns of bites. We also propose a set of recommendations for communities and local hospitals including the necessity of hospitalization and antivenin administration for patients exhibiting serious symptoms. Conclusion: It is important to document envenomation accidents, symptoms, and treatment protocol. Furthermore, traditional medicine practices should be reported as they can interfere with or even hinder medical treatment. The results of this article will certainly apply to a wider range of countries in the region. [ABSTRACT FROM AUTHOR]

Abstract Background Microbiomes can have profound impacts on host biology and evolution, but to date, remain vastly understudied in spiders despite their unique and diverse predatory adaptations. This study evaluates closely related species of spiders and their host-microbe relationships in the context of phylosymbiosis, an eco-evolutionary pattern where the microbial community profile parallels the phylogeny of closely related host species. Using 16S rRNA gene amplicon sequencing, we characterized the microbiomes of five species with known phylogenetic relationships from the family Theridiidae, including multiple closely related widow spiders (L. hesperus, L. mactans, L. geometricus, S. grossa, and P. tepidariorum). Results We compared whole animal and tissue-specific microbiomes (cephalothorax, fat bodies, venom glands, silk glands, and ovary) in the five species to better understand the relationship between spiders and their microbial symbionts. This showed a strong congruence of the microbiome beta-diversity of the whole spiders, cephalothorax, venom glands, and silk glands when compared to their host phylogeny. Our results support phylosymbiosis in these species and across their specialized tissues. The ovary tissue microbial dendrograms also parallel the widow phylogeny, suggesting vertical transfer of species-specific bacterial symbionts. By cross-validating with RNA sequencing data obtained from the venom glands, silk glands and ovaries of L. hesperus, L. geometricus, S. grossa, and P. tepidariorum we confirmed that several microbial symbionts of interest are viably active in the host. Conclusion Together these results provide evidence that supports the importance of host-microbe interactions and the significant role microbial communities may play in the evolution and adaptation of their hosts.

Abstract Humankind has always been fascinated by venomous animals, as their toxic substances have transformed them into symbols of power and mystery. Over the centuries, researchers have been trying to understand animal venoms, unveiling intricate mixtures of molecules and their biological effects. Among venomous animals, Latrodectus Walckenaer, 1805 (widow spiders) have become feared in many cultures worldwide due to their extremely neurotoxic venom. The Latrodectus genus encompasses 32 species broadly spread around the globe, 14 of which occur in the Americas. Despite the high number of species found in the New World, the knowledge on these spiders is still scarce. This review covers the general knowledge on Latrodectus spp. from the Americas. We address widow spiders’ taxonomy; geographical distribution and epidemiology; symptoms and treatments of envenomation (latrodectism); venom collection, experimental studies, proteome and transcriptome; and biotechnological studies on these Latrodectus spp. Moreover, we discuss the main challenges and limitations faced by researchers when trying to comprehend this neglected group of medically important spiders. We expect this review to help overcome the lack of information regarding widow spiders in the New World.

Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient’s history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future.

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Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient's history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future. [ABSTRACT FROM AUTHOR]

Eggs of black widow spiders in the genus Latrodectus Walckenaer, 1805 (Theridiidae) are known to be toxic when injected into mammals. We surveyed eggs from 39 species of spiders in 21 families to determine if spider egg toxicity is a unique property of widow spiders, or if spider egg toxicity is associated with other spider taxa. Eggs from 13 species of spiders in three families were determined to be highly lethal to mice, eggs from four species in four families were moderately lethal, and eggs from 22 species in 17 families lacked detectable lethality. Egg lethality appears to have evolved multiple times in spiders within the Araneidae, Theridiidae, and Agelenidae, and possibly also within the Tetragnathidae, Pimoidae, and Linyphiidae. These toxins in the various spiders may have differing chemical structures and could represent new sources of toxins that may be of future research interest. [ABSTRACT FROM AUTHOR]

Latrodectism or envenomation by widow-spiders is common and clinically significant worldwide. Alpha-latrotoxin is the mammalian-specific toxin in the venom that results in toxic effects observed in humans. Symptoms may be incapacitating and include severe pain that can persist for days. The management of mild to moderate latrodectism is primarily supportive while severe cases have variously been treated with intravenous calcium, muscle relaxants, widow-spider antivenom and analgesic opioids. The object of this systematic review is to examine the literature on the clinical effectiveness of past and current treatments for latrodectism. MEDLINE, EMBASE and Google Scholar were searched from 1946 to December 2016 to identify clinical studies on the treatment of latrodectism. Studies older than 40 years and not in English were not reviewed. There were only two full-publications and one abstract of placebo-controlled randomised trials on antivenom use for latrodectism. Another two randomised comparative trials compared the route of administration of antivenom for latrodectism. There were fourteen case series (including two abstracts), fourteen case reports and one letter investigating drug treatments for latrodectism with the majority of these also including antivenom for severe latrodectism. Antivenom with opioid analgesia is often the major treatment reported for latrodectism however; recent high quality evidence has cast doubt on the clinical effectiveness of this combination and suggests that other treatments need to be investigated. [ABSTRACT FROM AUTHOR]

Background: Nowadays use of specific antivenin for latrodectism is considered as the most effective treatment in the world. This study was undertaken to investigate the efficacy of specific antivenom against histopathological complications caused by Latrodectus dahli venom on liver, heart and kidneys tissues within 72h. Methods: Two groups were selected, each one contained 6 male New Zealand rabbits weighing 2±0.5kg. The ani- mals were anesthetized with 0.5ml ketamine and 0.5ml xylazine by intramuscular route. The L. dahli venom (0.5mg/kg) was injected subcutaneously to both the groups. The second group of rabbits 24h after the venom injection received specific antivenom by intravenous route. Seventy-two hours after the venom and antivenom injections, the rabbits were dissected to obtain heart, liver and kidney tissues. The tissues were stained by hematoxylin and eosin stains and histopathological studies were examined by optical microscope. Results: In group one, the venom induced myocytolysis, myocarditis, coagulation necrosis in the heart tissue and the liver tissue showed central vein congestion, congested vessels, dilated sinusoids and inflammation. However, no significant histopathological complications were observed in kidney tissues. In the second group, antivenom injection greatly prevented escalation of the complications on foresaid tissues. Conclusion: Latrodectus dahli venom induces histopathological complications on vital organs. Specific antivenom injection, 24h after the venom injection, could protect the tissues from incidence and intensification of histopathological complications. Future studies in human beings should be conducted to assess the protection against the spe- cific-Latrodectus antivenin. [ABSTRACT FROM AUTHOR]

Latrodectus tredecimguttatus is a kind of highly venomous black widow spider, with toxicity coming from not only venomous glands but also other parts of its body as well as newborn spiderlings and eggs. Up to date, although L. tredecimguttatus eggs have been demonstrated to be rich in proteinaceous toxins, there is no systematic investigation on such active components at transcriptome level. In this study, we performed a high-throughput transcriptome sequencing of L. tredecimguttatus eggs with Illumina sequencing technology. As a result, 53,284 protein-coding unigenes were identified, of which 14,185 unigenes produced significant hits in the available databases, including 280 unigenes encoding proteins or peptides homologous to known proteinaceous toxins. GO term and KEGG pathway enrichment analyses of the 280 unigenes showed that 375 GO terms and 18 KEGG pathways were significantly enriched. Functional analysis indicated that these unigene-coded toxins have the bioactivities to degrade tissue proteins, inhibit ion channels, block neuromuscular transmission, provoke anaphylaxis, induce apoptosis and hyperalgesia, etc. No known typical proteinaceous toxins in L. tredecimguttatus venomous glands, such as latrotoxins, were identified, suggesting that the eggs have a different toxicity mechanism from that of the venom. Our present transcriptome analysis not only helps to reveal the gene expression profile and toxicity mechanism of the L. tredecimguttatus eggs, but also provides references for the further related researches. [ABSTRACT FROM AUTHOR]

Background: Latrodectism, a syndrome caused by Latrodectus genus, is one of the clinical problems that occur predominantly in north east of Iran. Nowadays antivenom therapy has become the most useful treatment for animal bites; however there is still a controversy about route and time of antivenom administration in spider bite. The aim of the present study was to determine the efficacy of specific antivenom in neutralizing hepatic and renal symptoms 24 h after Latrodectus dahli envenomation. Methods: We selected a group of male New Zealand white rabbits, weighing 2±0.3 kg. The L. dahli venom (0.5 mg/kg) was injected subcutaneously. Specific antivenom (2.5 ml, I.V) was injected 24 h following venom injection. Blood sampling was performed before and 24 h after venom injection, as well within 24, 48 and 72 h after antivenom administration. Serum levels of (aspartate amino transferase (AST) alanine amino transferase (ALT), alkaline phosphatase (ALP), urea, bilirubin, creatinine and albumin were determined in all the sam. Results: Latrodectus dahli venom caused significant increase (P< 0.05) in all foresaid serum parameters. Antivenom reversed the AST, ALP, creatinine, urea and bilirubin to normal levels, but failed about ALT level, also nonsignificant decrease was observed in albumin levels. Conclusion: Antivenom administration 24 h after venom injection can greatly reverse symptoms caused by venom. Future studies in human beings should be conducted to assess the protection against the specific-Latrodectus antivenom. [ABSTRACT FROM AUTHOR]

Gene duplication and positive selection can be important determinants of the evolution of venom, a protein-rich secretion used in prey capture and defense. In a typical model of venom evolution, gene duplicates switch to venom gland expression and change function under the action of positive selection, which together with further duplication produces large gene families encoding diverse toxins. Although these processes have been demonstrated for individual toxin families, high-throughput multitissue sequencing of closely related venomous species can provide insights into evolutionary dynamics at the scale of the entire venom gland transcriptome. By assembling and analyzing multitissue transcriptomes from the Western black widow spider and two closely related species with distinct venom toxicity phenotypes, we do not find that gene duplication and duplicate retention is greater in gene families with venom gland biased expression in comparison with broadly expressed families. Positive selection has acted on some venom toxin families, but does not appear to be in excess for families with venom gland biased expression. Moreover, we find 309 distinct gene families that have single transcripts with venom gland biased expression, suggesting that the switching of genes to venom gland expression in numerous unrelated gene families has been a dominant mode of evolution. We also find ample variation in protein sequences of venom gland-specific transcripts, lineage-specific family sizes, and ortholog expression among species. This variation might contribute to the variable venom toxicity of these species. [ABSTRACT FROM AUTHOR]

Widow spiders have received much attention due to the frequently reported human and animal injures caused by them. Elucidation of the molecular composition and action mechanism of the venoms and toxins has vast implications in the treatment of latrodectism and in the neurobiology and pharmaceutical research. In recent years, the studies of the widow spider venoms and the venom toxins, particularly the-latrotoxin, have achieved many new advances; however, the mechanism of action of the venom toxins has not been completely clear. The widow spider is different from many other venomous animals in that it has toxic components not only in the venom glands but also in other parts of the adult spider body, newborn spiderlings, and even the eggs. More recently, the molecular basis for the toxicity outside the venom glands has been systematically investigated, with four proteinaceous toxic components being purified and preliminarily characterized, which has expanded our understanding of the widow spider toxins. This review presents a glance at the recent advances in the study on the venoms and toxins from the Latrodectus species. [ABSTRACT FROM AUTHOR]

Background: The longstanding canonical model of spider gastrulation posits that cell internalization occurs only at a unitary central blastopore; and that the cumulus (dorsal organizer) arises from within the early deep layer by cell-cell interaction. Recent work has begun to challenge the canonical model by demonstrating cell internalization at extrablastoporal sites in two species (Parasteatoda tepidariorum and Zygiella x-notata); and showing in Zygiella that the prospective cumulus internalizes first, before other cells are present in the deep layer. The cell behaviors making up spider gastrulation thus appear to show considerable variation, and a wider sampling of taxa is indicated. Results: We evaluated the model in three species from two families by direct observation of living embryos. Movements of individual cells were traced from timelapse recordings and the origin and fate of the cumulus determined by CM-DiI labeling. We show that there are two distinct regions of internalization: most cells enter the deep layer via the central blastopore but many additional cells ingress via an extra-blastoporal ring, either at the periphery of the germ disc (Latrodectus spp.) or nearer the central field (Cheiracanthium mildei). In all species, the cumulus cells internalize first; this is shown by tracing cells in timelapse, histology, and by CM-DiI injection into the deep layer. Injection very early in gastrulation labels only cumulus mesenchyme cells whereas injections at later stages label non-cumulus mesoderm and endoderm. Conclusions: We propose a revised model to accommodate the new data. Our working model has the prospective cumulus cells internalizing first, at the central blastopore. The cumulus cells begin migration before other cells enter the deep layer. This is consistent with early specification of the cumulus and suggests that cell-cell interaction with other deep layer cells is not required for its function. As the cumulus migrates, additional mesendoderm internalizes at two distinct locations: through the central blastopore and at an extra-blastoporal ring. Our work thus demonstrates early, cell-autonomous behavior of the cumulus and variation in subsequent location and timing of cell internalization during gastrulation in spiders. [ABSTRACT FROM AUTHOR]

The evolution of specialized tissues with novel functions, such as the silk synthesizing glands in spiders, is likely an influential driver of adaptive success. Large-scale gene duplication events and subsequent paralog divergence are thought to be required for generating evolutionary novelty. Such an event has been proposed for spiders, but not tested. We de novo assembled transcriptomes from three cobweb weaving spider species. Based on phylogenetic analyses of gene families with representatives from each of the three species, we found numerous duplication events indicative of a whole genome or segmental duplication. We estimated the age of the gene duplications relative to several speciation events within spiders and arachnids and found that the duplications likely occurred after the divergence of scorpions (order Scorpionida) and spiders (order Araneae), but before the divergence of the spider suborders Mygalomorphae and Araneomorphae, near the evolutionary origin of spider silk glands. Transcripts that are expressed exclusively or primarily within black widow silk glands are more likely to have a paralog descended from the ancient duplication event and have elevated amino acid replacement rates compared with other transcripts. Thus, an ancient large-scale gene duplication event within the spider lineage was likely an important source of molecular novelty during the evolution of silk gland-specific expression. This duplication event may have provided genetic material for subsequent silk gland diversification in the true spiders (Araneomorphae). [ABSTRACT FROM AUTHOR]

During the summer period 2011-2012, seven widow spider bites in Greece were reported to the Hellenic Center for Disease Control and Prevention. Widow spiders (in the genus Latrodectus) are found all over the world, including Europe, Asia, Africa, Australia, and the US. Alpha-latrotoxin (main mammalian toxin) causes the toxic effects observed in humans. Victims should receive timely medical care to avoid suffering. Latrodectus bites are very rarely fatal. All the patients reported having an insect bite 30 minutes to 2 hours before they arrived at the Emergency Department of the local hospital. Severe muscle cramps, weakness, tremor, abdominal pain, and increased levels of creatinine phosphokinase were present in all patients. The Emergency Operation Center of the Hellenic Center for Disease Control and Prevention was informed immediately in all cases. Antivenin was administered to four patients upon the request of their physicians. All patients recovered fully. It is essential that health care workers recognize early the symptoms and signs of Latrodectus bites to provide the necessary care. The management of mild to moderate Latrodectus envenomations is primarily supportive. Hospitalization and possibly antivenin should be reserved for patients exhibiting serious systemic symptoms or inadequate pain control. The most important thing for all of these patients is early pain relief. [ABSTRACT FROM AUTHOR]

Spatial associations between the invasive tree lupin (Lupinus arboreus), the New Zealand endemic widow spider Latrodectus katipo (katipo), and the introduced South African spider Steatoda capensis (false katipo) were examined within the nationally significant Kaitorete Spit dune system in Canterbury, New Zealand. These dunes are considered to be a stronghold for L. katipo, but with the decline in preferred vegetation for capture-web attachment as a result of tree lupin invasion, a decline in the spider's population was expected. On other New Zealand dune systems a decline in L. katipo abundance has corresponded with an increase in the abundance of the introduced S. capensis. Spider population data collected over a 6-year period and vegetation data collected in 2008 and 2009 were used to examine the spatial associations at Kaitorete Spit. The abundance of S. capensis was not significantly related to the abundance of L. katipo. The ratio of S. capensis to L. katipo declined annually over the 6 years. The 2008 and 2009 vegetation surveys found that S. capensis was not located in areas where tree lupin was present. Latrodectus katipo was found in areas with up to 40% tree lupin cover. The abundance of L. katipo recorded in areas dominated by tree lupin was not significantly different from the abundances recorded in association with native plant cover. The presence of L. arboreus at Kaitorete Spit is not considered to be a direct threat to the population of L. katipo; Kaitorete Spit is still a stronghold. [ABSTRACT FROM AUTHOR]

Background: In order to describe the patients and evaluate the effectiveness of treatments for widow spider envenomation, investigators require a reliable assessment tool. In this paper, the development of a clinical index for measuring the widow spider bite severity, Latrodectus Envenomation Severity Score (LESS), is described. Methods: According to the valid methods for index development, a Delphi group process was applied. A panel of 13 experienced medical toxicologists and physician experts in treatment of black widow spider bites was assembled in December 2013. The participants were asked to score clinical manifestations of Latrodectus envenomation based on their importance on the severity and patients' prognosis. Hence, an initial draft of the severity index was developed and in the second phase of study, the draft was discussed in a focus group of experts to finally comment on each variable and vote about the final scores. Results: The proposed version of LESS comprises of 34 clinical items categorized in 8 organ systems. The index includes definition of each clinical variable to help users of the index how to ascertain or rule out the clinical finding. The maximum theoretical score according to LESS is 87. Acute renal failure, myocarditis, pulmonary edema and ileus received the highest scores in this index . Conclusion: The LESS is a new assessment tool that is designed to more objectively evaluate the severity and progression of envenomation in victims of widow spider bite. The prognostic-ability, reliability and sensitivity to change of the index should be investigated in future studies. [ABSTRACT FROM AUTHOR]

The red widow spider, Latrodectus bishopi Kaston, is a species of conservation concern because it is narrowly endemic to threatened palmetto scrub found only on ancient sand ridges in peninsular Florida. We hypothesized that this spider might feed extensively on insects that also are scrub specialists. To ascertain the prey of red widow spiders, we collected arthropods trapped in webs of adult females ( n = 30 per season) located in native oak-palmetto scrub at the Archbold Biological Station after dawn and before dusk for 5 consecutive days in early spring (Mar 1989) and in late spring (May 2003). We identifed a total of 42 species among the 98 specimens collected. Using published regression equations, we converted the size of each specimen to dry mass. We found that 5 species of scarab beetles endemic to Florida scrub accounted for 65% of prey by weight even though their numbers were modest (22% of prey items). In early spring red widow spiders fed predominantly on nocturnally captured coleopterans (78% of prey items), but in late spring when palmetto flowers were blooming near webs day-active hymenopterans were added to the diet. Frequency analysis showed that temporal patterns of prey capture by individual spiders were infrequent (≤ 0.4 prey per day) and statistically random. [ABSTRACT FROM AUTHOR]

Following the hospitalization of 195 individuals due to the spider bite in 1995 and three cases of recorded death in the year of 1993 which were referred to Emam Reza Hospital in Mashad, the present study was undertaken on bionomics and medical importance of Lathrodectus spp in Khorasan Province, during 1995-2005. A total cases of 195 bites were studied composing of 70.8 % males and 29.2% females. The most prevalence cases were observed in mid age (20-55 years old) and par¬ticularly among farmers (36.4%). A total number of 216 adult widow spiders and 258 egg sacs were collected from their habitats in different localities of 15 counties in the province. The following species have been recognized: Lathrodectus tredecimgottatus (62%), L. dahli (32%), L. geometricus (5%) and L. pallidus (1%). Here is the first report on the occurrence of males of L. pallidus as well as both sexes of L. trdecimgottatus and L. geometricus in the country. The sex ratio among collected specimens was 88% and 12% female and male, respectively. Summer provides the most suitable and favorable climatic condition for the activities of these spiders. However 65% of spiders were collected in this season. Among different cit¬ies, Mashad had (60%) the most reported cases in the study area. Foot was more injured than other parts. 96.5% of pa¬tients exhib¬ited localized pain from which only 2% had no pain in the bitten part and 87% had a generalized pain in whole body.

The article presents a study on the feeding ecology of the black widow spider Latrodectus mirabilis in wheat and oat fields of central Argentina to examine their diet composition and capture rate of leaf-cutting ants. The study identified 1,004 prey items that had been captured by the spiders. It was found that the spiders prey mainly on the ants Formicidae and Hymenoptera. Their diet is said to be polyphagous because they prey upon varied arthropods but with a high proportion of one item.

Three Threidiid spiders of the genus Latrodectus occur in Khorasan province: L.tredecimguttatus, L.pallidus, L.dahli. The three are described, their diagnostic features are illustrated, and taxonomic notes are given where possible. Spider bites are very common in these regions, so, further notes about the medical importance of these species are given. A dichotomic key to the species of the genus Latrodectus is presented.

The article focuses on the clinical profile of spider bite in southern Africa, citing that the diagnosis can be difficult particularly if the patient is unaware of having been bitten. The medically important spiders are classified into two groups including the neurotoxic, belonging to the genus Latrodectus (button or widow spiders), and the cytotoxic, belonging to the genus Cheiracanthium (sac spiders) and Laxosceles (violin or recluse spiders).

The article presents the first report of the widow spider Theridiidae from the genus Latrodectus elegans from India. It notes that the comb-foot spider species has clinical significance due to the three species being reported from India. It also explores the variability within the 31 spider species in their different stages of growth.

Research on consistent individual differences in behavior, or 'behavioral syndromes', continues to grow rapidly, and yet, the aspects of behavior under consideration have remained remarkably limited. Here, we consider individual variation in consistency of choice (termed here 'choosiness'), as expressed during habitat choice. We repeatedly tested the responses of female Western Black Widows, Latrodectus hesperus, to two cues of habitat quality: prey chemical cues and variation in web site illuminance. We estimated females' response by the distance they positioned themselves from (1) the source of prey chemical cues and (2) the darkest edge of our test arena. Individuals with low variance in their responses are deemed more 'choosy', whereas individuals with high variance are deemed less 'choosy'. Generally, most females initiated web construction near the source of the prey chemical cues and tended to place themselves in low-light conditions. However, we detected strong, repeatable differences in females' intensity of response, and within-individual variance of response (i.e., choosiness) was correlated across situations: females with highly consistent responses towards cricket chemical cues also exhibited highly consistent responses towards variation in light conditions. When deprived of food for extended periods, females were indistinguishable in their responses towards prey chemical cues, but tended to initiate web construction in brighter lighting conditions. Food-deprived females universally exhibited higher variance and diminished consistency in their responses (i.e., they were less choosy). Additionally, higher choosiness was associated with greater mass loss during choice trials, suggesting choosiness is energetically costly. Our results demonstrate that consistency of response to environmental cues is yet another element of behavior that varies among individuals and variation in choosiness could beget speed/quality trade-offs during animal decision making. [ABSTRACT FROM AUTHOR]

Since the 1970s, There have been studies of the venom of Latrodectus sp. spiders, in particular the latrotoxin (LTX) of Latrodectus mactans. Many of the studies were aimed at understanding the action of the venom on the muscular system. Now accepted that LTX is able to generate a calcium-permeable membrane pore and modulate the release of synaptic vesicles that activate a receptor and induce cellular changes. Interestingly, when work began with venom obtained from the Latrodectus sp present in Chile, it generated clinical indications similar to the bite of this spider in another country, with some differences in intensity. The purpose of the first studies was to understand the systemic mechanisms of this venom, and other active compounds were studied for biological interest. It was found that these molecules are capable of causing systemic effects such as changes in muscle contraction: of generating vascular relaxation and synaptic and cellular modulation; and of altering potassium conductance channels. Based on this evidence, we suggested biotechnological applications to characterize low molecular-weight compounds obtained from the Chilean Latrodectus venom and exploring the effects on the eleetrophysiology in oocytes and neurons, and the contraceptive effect on spermatozoa. [ABSTRACT FROM AUTHOR]

Web designs of young spiders are often less derived than those of older conspecific individuals. This study tested whether this "ontogeny repeats phylogeny" pattern occurs in two species of Latrodectus and two species of the closely related genus Steatoda. This pattern was assumed to occur in a recent study of a third Latrodectus species, L geometricus, which attempted to deduce a probable evolutionary derivation of gum-foot webs of theridiids on the basis of ontogenetic changes. We found the same basic ontogeny repeats phylogeny ontogenetic pattern in all four species, suggesting that the previous suppositions were justified. As expected, the webs of the young instars of the two Latrodectus species were more similar than those of the adults, and were more similar to those of young than to those of adults of L. geometricus. One apparently derived trait of L. mirabilis, attaching prey remains as camouflage for the spider in the central portion of the web, did not change during ontogeny, and was present in even the webs of first-instar spiderlings. Field observations of L. mirabilis suggest that the ontogenetic change from light to darker abdominal color patterns that occurs in many Latrodectus species may result from changes in selection for camouflage associated with ontogenetic changes in web designs and the spiders' resting sites. The webs of Steatoda also fit the ontogenetic pattern: at least some ontogenetic changes in both species involved younger spiders having less derived traits than those of adults. The webs of young Steatoda spiders were more derived in some respects than those of the early instars of Latrodectus [ABSTRACT FROM AUTHOR]

Spiders spin a variety of task-specific silk fibers, each composed of one or more unique proteins synthesized within specialized glands in the spider's abdomen. Tubuliform glands are the source of the large diameter silk fibers used by many species in the construction of egg cases. Unlike other silk glands that synthesize protein throughout a spider's lifetime, the tubuliform glands synthesize silk in association with the maturation of oocytes, culminating in the production of an egg case. In the Western black widow, Lactrodectus hesperus Chamberlin & lvie (1935), egg case fibers are composed of at least three proteins: tubuliform spidroin 1(TuSpl), egg case protein-1/ECP-1), and egg case protein-2 (ECP-2). Here, we present the first study to quantify the pattern of transcription for these three genes in a developmental series of tubuliform glands from L. hesperus. All three transcripts increase in abundance prior to the production of an egg case, but at different time points. After egg case production, silk transcripts are still detectable in the tubuliform glands. Relative abundance of TuSpl mRNA is several orders of magnitude higher than that of ECP-1 and ECP-2 at almost every stage. The relative abundance of silk transcripts across the reproductive life history of black widows suggests differential regulation of silk gene transcription within tubuliform glands. [ABSTRACT FROM AUTHOR]

We used experimental manipulations to test adaptive explanations for the courtship display of the male widow spider, Latrodectus pallidus O. Pickard-Cambridge 1872. Two hypotheses have been suggested to explain a long and complex male display: a) Cooperation of males and females in the effort to physically stimulate the female. As the time of male arrival is not predictable, females may delay sexual readiness until the appearance of a courting male, b) Conflict between males and females regarding the display cost. Females impose on the males an energetically costly display that may last several hours as a test of their quality. To test both hypotheses, we manipulated the previous experience of either the male or the female. We presented naive or experienced males (males that had courted and were accepted by females but were prevented from copulating) to females that were either naive or experienced (had been courted by a male but prevented from copulating). We also presented naive males to mated females. Following the stimulation hypothesis, courted females were presumed to have been stimulated to mate and thus were expected to accept non-courting males as mates. Both naive and mated females, however, were expected to await male stimulation before allowing copulation. In contrast, the conflict of interest hypothesis predicts that the female tests each male for quality indicators and therefore a non-courting male should not be accepted as a mate. Mated females, however, should apply a less stringent test to courting males. Our results show that 1) naive females prevented males that did not perform a full courtship display from entering the nest and mounting; 2) naive males courted virgin females with the full display, independent of the female previous courting history; and 3) naive males shortened their courtship when presented with mated females. The results are consistent with the conflict of interest hypothesis. [ABSTRACT FROM AUTHOR]

Mixed species associations are of general importance because of the diversity of ecological relations they can represent (e.g., mutualisms, commensalisms, exploitative relationships). We test for a non-random association between two normally solitary species of spider, the black widow (Latrodectus mactans) and the orchard spider (Leucage venusta). We use field observations comparing solitary and associated individuals of both species to elucidate what effect the association has on prey capture. We then evaluate what influence the association has on prey consumption, as inferred from change in body mass after a reciprocal removal experiment. From our field census we confirm that these species associate non-randomly in wild populations; furthermore, we failed to detect a difference in the number or kinds of prey which hit solitary and associated webs of either species, suggesting the association is not merely an aggregation to microhabitats which afford higher prey availability. Our observational data on prey capture indicate the association serves to increase the capture efficiency of Le. venusta, in part through ricocheted prey, but we failed to detect a prey capture effect for La. mactans. The results of our reciprocal removal experiment suggest the relationship is a commensalism: benefiting Le. venusta and leaving La. mactans unaffected. [ABSTRACT FROM AUTHOR]

Quantifying primary sex ratios is necessary for studies in a wide range of areas including adaptive sex ratio modification, population demography, and sex-biased developmental mortality. Adult and penultimate male spiders are easy to sex, due to the great thickening of the male pedipalps, which are used for delivering sperm to the female reproductive tract. However, in many spider species, males and females are apparently monomorphic at hatching, are difficult to rear, and cannibalize their siblings, making assessment of primary sex ratios problematic. One technique for sexing spiders is karyotyping, but this can be challenging and time-consuming, particularly for species with high fecundity, and often requires destructive sampling. Here we report that, although apparently monomorphie, early-instar juveniles of two species of black widow spiders (Latrodectus hasselti Thorell 1870 and Latrodectus hesperus Chamberlin & Ivie 1935) can be sexed reliably. Palp width measurements are significantly different for males and females at the 3rd instar, with the palpi of juvenile females thinner than those of males. Moreover, sex identification with 89-100% accuracy can be achieved by an experienced observer visually inspecting the palpi of 3rd instar spiderlings under a dissecting microscope. Our results suggest that minimal investment in a pilot study can yield an accurate method for sexing juvenile spiders in the laboratory or field. The suitability of this method should be examined in other species with apparently monomorphic spiderlings, particularly those in which adult males have significantly enlarged palpi. [ABSTRACT FROM AUTHOR]

Spiders spin high-performance silks through the expression and assembly of tissue-restricted fibroin proteins. Spider silks are composite protein biopolymers that have complex microstructures. Retrieval of cDNAs and genomic DNAs encoding silk fibroins has revealed an association between the protein sequences and structure-property relationships. However, before spider silks can be subject to genetic engineering for commercial applications, the complete protein sequences and their functions, as well as the details of the spinning mechanism, will require additional progress and collaborative efforts in the areas of biochemistry, molecular biology and material science. Novel approaches to reveal additional molecular constituents embedded in the spider fibers, as well as cloning strategies to manipulate the genes for expression, will continue to be important aspects of spider biology research. Here we summarize the molecular characteristics of the different spider fibroins, the mechanical properties and assembly process of spidroins and the advances in protein expression systems used for recombinant silk production. We also highlight different technical approaches being used to elucidate the molecular constituents of silk fibers. [ABSTRACT FROM AUTHOR]

Many sperm competition studies have identified copulation duration as an important predictor of paternity. This result is often interpreted as a sperm transfer effect—it is assumed that sperm transfer is limited by copulation duration. Here we test the assumption of duration-dependent sperm transfer in the Australian redback spider, Latrodectus hasselti, in which a correlation between copulation duration and paternity has been implicated in the evolution of a rare male self-sacrifice behavior. Male redbacks facilitate sexual cannibalism by females during copulation. Sexual cannibalism is apparently adaptive for redback males, in part because it results in longer copulations (25 versus 11 min.), and copulation duration is positively correlated with paternity. We assessed sperm transfer in normal copulations and in copulations that we terminated at 5, 10, or 20 min. Our results show that the paternity advantage of sexual cannibalism is not owing to time-dependent sperm transfer, as redback males transfer the majority of their sperm within the first 5 min of copulation. This suggests that the link between copulation duration and paternity may instead be owing to cryptic female choice or the transfer of nongametic ejaculatory substances. Results further indicate that the act of cannibalism itself might play a role in mediating sperm transfer. This study highlights the importance of understanding mechanisms of sperm transfer when attempting to interpret the outcome of sperm competition studies. [ABSTRACT FROM AUTHOR]

Male redback spiders twist their abdomens onto the fangs of their mates during copulation and, if cannibalized (65% of matings), increase their paternity relative to males that are not cannibalized. The adaptive male sacrifice hypothesis proposes that this increased reproductive payoff from a single mating outweighs the residual reproductive value of a cannibalized male, because high mortality during mate searching restricts alternative mating opportunities. It has been reported that redback male residual reproductive value is low because males are functionally sterile after one mating—a putative intrinsic constraint that could arguably favor self-sacrifice in the absence of ecological restrictions on multiple mating. However, sterility and self-sacrifice may both arise as aspects of a terminal investment strategy if the probability of multiple mating is sufficiently low. Here I report field data that support the adaptive male sacrifice hypothesis. More than 80% of redback males die without finding a potential mate in nature. Data from two observational field studies and one release experiment suggest that in the absence of cannibalism, male redbacks would expect fewer than one mating opportunity in a lifetime. This expectation was not significantly higher for a large male or one in good condition. A simple quantitative analysis confirms that even if males are assumed to be fertile throughout life, the measured mortality rate during mate search in combination with previously documented paternity benefits of cannibalism is sufficient to ensure that self-sacrifice is adaptive for male redback spiders. [ABSTRACT FROM AUTHOR]

Investigates web relocation and habitat selection in the widow spider, Latrodectus revivensis. Examination of relationships between movement, habitat and components of fitness; Spatial and temporal patterns of movement; Causes, costs and fitness consequences of shifting habitat; Increased mortality as main cost; Prey availability; Advantages of web relocation.

A cDNA encoding a polypeptide of 88 amino acids was cloned following the rapid amplification of cDNA ends (RACE) procedure using mRNA isolated from the venom glands of the Mediterranean black widow spider (Latrodectus tredecimguttatus) and oligonucleotides based on the sequence of a tryptic fragment putatively from α-latrotoxin. Apart from a potential signal peptide, the rest of this small protein, named latrodectin, was highly hydrophilic, having a calculated molecular mass of 7945 Da and a pI of 4.3. Northern-blot analysis showed that the mRNA was specifically expressed in the venom gland of L. tredecimguttatus and that it was well conserved between two geographically remote species (L. geometricus and L. indistinctus). A polyclonal serum raised in rabbits against the C-terminal sequence of latrodectin detected cross-reactive proteins in the venom fluid, venom gland extracts, and in purified α-latrotoxin, suggesting that latrodectin is intimately associated with α-latrotoxin. Finally, we produced a recombinant protein in a cell system infected with baculovirus and developed an immunoaffinity purification procedure for latrodectin to facilitate further structural and functional analyses of the molecule. [ABSTRACT FROM AUTHOR]

When threatened, the black widow spider, Latrodectus hesperus, emits an adhesive, viscous web, pulls the strand from its spinnerets with its fourth pair of legs, and spreads its appendages. This behavior positions the web over the delicate abdomen, increases the area of protection, and enables the spider to place the web onto the offender, if necessary. In laboratory interactions, the viscous web protected black widows from mice (Peromyscus spp.). Mature female spiders, which had their spinnerets blocked and hence could not discharge the viscid silk, escaped less often than did black widows that were not experimentally altered. The viscid silk is palatable to mice and it appears that the deterrent effect of the web is due solely to mechanical irritation. The defensive behavior is elicited most often from mature females, which may suffer greater predation than other age groups. Males lose the ability to produce the defensive web at maturity and may shift their energy resources totally into reproductive effort. [ABSTRACT FROM AUTHOR]

Humankind has always been fascinated by venomous animals, as their toxic substances have transformed them into symbols of power and mystery. Over the centuries, researchers have been trying to understand animal venoms, unveiling intricate mixtures of molecules and their biological effects. Among venomous animals, Latrodectus Walckenaer, 1805 (widow spiders) have become feared in many cultures worldwide due to their extremely neurotoxic venom. The Latrodectus genus encompasses 32 species broadly spread around the globe, 14 of which occur in the Americas. Despite the high number of species found in the New World, the knowledge on these spiders is still scarce. This review covers the general knowledge on Latrodectus spp. from the Americas. We address widow spiders' taxonomy; geographical distribution and epidemiology; symptoms and treatments of envenomation (latrodectism); venom collection, experimental studies, proteome and transcriptome; and biotechnological studies on these Latrodectus spp. Moreover, we discuss the main challenges and limitations faced by researchers when trying to comprehend this neglected group of medically important spiders. We expect this review to help overcome the lack of information regarding widow spiders in the New World., Competing Interests: Competing interests: The authors declare that they have no competing interests.

Background: Microbiomes can have profound impacts on host biology and evolution, but to date, remain vastly understudied in spiders despite their unique and diverse predatory adaptations. This study evaluates closely related species of spiders and their host-microbe relationships in the context of phylosymbiosis, an eco-evolutionary pattern where the microbial community profile parallels the phylogeny of closely related host species. Using 16S rRNA gene amplicon sequencing, we characterized the microbiomes of five species with known phylogenetic relationships from the family Theridiidae, including multiple closely related widow spiders (L. hesperus, L. mactans, L. geometricus, S. grossa, and P. tepidariorum). Results: We compared whole animal and tissue-specific microbiomes (cephalothorax, fat bodies, venom glands, silk glands, and ovary) in the five species to better understand the relationship between spiders and their microbial symbionts. This showed a strong congruence of the microbiome beta-diversity of the whole spiders, cephalothorax, venom glands, and silk glands when compared to their host phylogeny. Our results support phylosymbiosis in these species and across their specialized tissues. The ovary tissue microbial dendrograms also parallel the widow phylogeny, suggesting vertical transfer of species-specific bacterial symbionts. By cross-validating with RNA sequencing data obtained from the venom glands, silk glands and ovaries of L. hesperus, L. geometricus, S. grossa, and P. tepidariorum we confirmed that several microbial symbionts of interest are viably active in the host. Conclusion: Together these results provide evidence that supports the importance of host-microbe interactions and the significant role microbial communities may play in the evolution and adaptation of their hosts. [ABSTRACT FROM AUTHOR]

Abstract: Theory suggests that males should adjust courtship in response to a variety of factors, including female quality, the risk of male-male competition, and often in spiders, the risk of sexual cannibalism. Male black widow spiders demonstrate a behavior during courtship whereby they tear down and bundle a female's web in addition to providing other vibratory and contact sexual signals. This web reduction has been hypothesized to play a role in all three factors (sexual signaling, competition reduction, and cannibalism reduction), but rarely are these tested together. Here, we test these hypotheses by conducting mating trials using the western black widow (Latrodectus hesperus) and measuring both male and female quality and behavior. Our results indicate that amount of web reduction is best predicted by female aggression, and not aspects of either male or female quality (e.g., body mass), or by the potential for the web to attract other males (e.g., web mass). Yet, actual mating success was best predicted by the proportion of web reduced. Furthermore, there was no consistent among-individual variation in either reduction behavior or male success, indicating that all variation in both measures was due to plasticity and/or other unaccounted-for male or female traits. Collectively, we conclude that the primary function of web reduction behavior is to reduce female aggression and thus the risk of sexual cannibalism, and that any other functions such as signaling and reducing male-male competition have relatively lower importance.Significance statement: Male widow spiders must account for female aggression, quality, and male-male competition when courting females. During courtship, males will reduce a female's web by tearing it down and bundling the silk, which may aid in all three of these issues. Our results demonstrate that males reduce the webs of aggressive females more, and less so to potentially reduce competition from other males or in response to female quality. Ultimate mating success was dictated by how much a male reduced the web of a given female. Finally, males showed no among-individual variation in reduction behavior, indicating that the extensive variation in this behavior is due solely to plasticity in response to the female. [ABSTRACT FROM AUTHOR]

As a black widow spider, Latrodectus tredecimguttatus has poisonous components not only in venomous glands but also in eggs. Our previous work had carried out a transcriptome analysis of the spider eggs in an attempt to probe into the molecular basis of the egg toxicity. A proteinaceous toxin, named Latroeggtoxin-V, was mined from the identified transcriptome. In this study, the gene of Latroeggtoxin-V was cloned and heterologously expressed, and the anticancer activity of the recombinant Latroeggtoxin-V (rLatroeggtoxin-V) was characterized. Activity assay found that rLatroeggtoxin-V could selectively act on breast cancer line MDA-MB-231 cells, not only arresting their cell cycle, inhibiting their proliferation and migration, but also inducing their apoptosis. Bioinformatics analysis suggested that Latroeggtoxin-V belongs to the ATPase inhibitor protein family and the further activity assay showed that the rLatroeggtoxin-V inhibited the activity of the Na+/K+-ATPase in MDA-MB-231 cells in a concentration-dependent manner, suggesting that the anticancer activity of Latroeggtoxin-V is based on its affecting the ion transport and receptor functions of Na+/K+-ATPase. The present work not only laid the foundation for the utilization of Latroeggtoxin-V in the anticancer drug development and the related fields, but also provided a new paradigm for exploration of the proteinaceous toxins under the direction of transcriptomics and bioinformatics. [ABSTRACT FROM AUTHOR]

The article discusses a research by Emily MacLeod and colleagues that was published in the periodical "Animal Behaviour" regarding the mating of male black widow spiders with well-fed females peformed in controlled field, and wild conditions to develop evolved traits in females.