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Four species of spiders intercepted at domestic ports were studied in this paper. The CO Ⅰsequences of which were amplified by PCR and compared with the CO Ⅰsequences of five species recorded in GenBank. And the sequence characteristics were analyzed and the phylogenetic tree was constructed. The results showed that there were significant genetic differences among different species of Latrodectus, and the CO Ⅰsequence could be used as a DNA barcode for molecular identification of different species of Latrodectus. [ABSTRACT FROM AUTHOR]

Objectives: Redback spider (RBS) antivenom (RBSAV) use appears to have decreased since the results of the RAVE‐2 antivenom efficacy study were released. The aims of this study were to assess change in RBSAV use over time and compare responses to treatment for antivenom and other analgesics. Methods: Retrospective audit of RBS bite referrals to a toxicology unit, from January 2010 to January 2022. Data included demographics, pain severity, treatment (analgesia or RBSAV), response to treatment, re‐presentation rate, adverse events, change in antivenom use over time. Results: Of 270 presentations, 157 with moderate or severe pain were included (RBSAV n = 51, analgesia n = 106). Median age was 39 years, n = 81 (51%) female. Those receiving antivenom were more likely to report severe pain n = 46/51 (84%) versus n = 68/106 (58%) (P = 0.006). Eighty‐three percent of antivenom doses were administered between 2010 and 2013. Analgesia‐only group received various combinations of paracetamol, NSAIDs, and opioids. In those receiving RBSAV, 17/48 (35%), 26/48 (54%), 5/48 (10%) reported a partial, complete or no reduction in pain, respectively, versus 30/77 (39%), 43/77 (58%) and 4/77 (5%), for analgesia‐only group. Post‐treatment pain was not recorded in three RBSAV and 28 analgesia‐only patients. Pain reduction was no different for intravenous and intramuscular antivenom. Re‐presentation for ongoing pain was more common in the analgesia‐only group, 16/106 (15%) versus 1/51 (2%) for antivenom (P = 0.013). Conclusion: Antivenom use fell over the study period. There was no difference in pain relief between RBSAV and analgesia‐only groups. RBSAV, regardless of route of administration, was no better than standard analgesics in pain reduction in the present study. [ABSTRACT FROM AUTHOR]

The brown widow spider, Latrodectus geometricus, is a hazardous and highly invasive species globally. One of the suggested mechanisms enhancing this spider's invasiveness is lower susceptibility to natural enemies compared to other widow species. The parasitoid wasp, Philolema latrodecti, is known to attack egg sacs of L. geometricus, as well as those of other species of Latrodectus. Despite its potential importance as a natural enemy of L. geometricus, little is known about the development of this wasp and factors mediating its parasitism success. We investigated the development of this parasitoid in two widow spider host species, one native to Israel, the white widow, L. pallidus, and the invasive brown widow, L. geometricus. We compared wasp developmental success in egg sacs exposed to increasing wasp densities. We found increased wasp emergence and brood size, and smaller emerging wasp body size with increasing wasp density. Across all wasp densities, more and larger parasitoids developed in the egg sacs of the native host species, L. pallidus, compared to the invasive host species, L. geometricus. Parasitoid sex ratio was highly female-biased and the proportion of males increased with wasp density, suggesting local mate competition. Overall, our results suggest that L. pallidus is a better host for the egg sac parasitoid P. latrodecti, which could give a competitive advantage to the less-affected invasive brown widow spider. [ABSTRACT FROM AUTHOR]

Invasive species are sometimes less susceptible to natural enemies compared to native species, but the mechanism is often unclear. Here we tested two potential mechanisms for lower parasitism of invasive species: density-dependent parasitism and preference for human-dominated habitats. We investigated how variation in host density and habitat type affect egg sac parasitism in two widow spider species (family Theridiidae). We compared parasitism on the egg sac of the brown widow, Latrodectus geometricus, an urban invasive species, and the white widow, Latrodectus pallidus, a species native to Israel. To investigate variation in host and parasitoid density, we measured nearest-neighbor distance between spider webs and parasitism rates in 16 sites, and in a single site monthly throughout a year. In L. pallidus, denser sites were more heavily parasitized (up to 55%) and parasitism rate increased with population density throughout the season. Extremely dense L. geometricus populations, however, had very low rates of parasitism (0–5%). We then conducted an egg sac transplant experiment in human-dominated and natural habitats. We found no parasitism of either species in the human-dominated habitat, compared to 30% parasitism of both species in the natural habitat. In addition, we found evidence for higher predation of L. pallidus than of L. geometricus egg sacs, particularly in the natural habitat. These combined results suggest that the human-dominated habitats inhabited by L. geometricus have a lower abundance of predators and parasites. We conclude that lower parasitism and predation in human-dominated habitats could contribute to the invasion success of L. geometricus. [ABSTRACT FROM AUTHOR]

Introduction: The black widow spider, Latrodectus mactans , stands out as one of the most medically significant arachnids due to its extensive geographic distribution in the United States and its ability to produce a potent neurotoxin, α-latrotoxin. This study aimed to describe the epidemiology of black widow spider exposures by month of exposure, geographic distribution, demographics, symptoms, treatment, and health system resource utilization between 2012 and 2022., Methods: This was a retrospective observational study using the US National Poison Data System, the data warehouse of the 55 US poison centers. A descriptive analysis of patient demographic data, month of exposure, clinical effects, level of healthcare received, and medical outcome was performed., Results: During the studied period, a total of 15,299 cases of Latrodectus spp exposures were reported to US poison centers. Exposures occurred with higher frequency in warm-weather states and during summer months. Almost half the cases were managed outside a healthcare facility (48.6%). Hospital admission was required for 10.0% of exposures. The most common therapies received were wound care (43.7%) and benzodiazepines (18.6%). Antivenom was administered in 3.4% (n=521) of exposures., Conclusions: Poison center data indicate that most black widow spider exposures result in minor consequences. Supportive care is the primary approach for black widow spider bites. Although antivenom use is infrequent, providers may seek administration guidance from toxicologists through local poison centers. This study underscores the pivotal role of poison centers in mitigating unnecessary healthcare visits and subsequent hospitalizations.

Envenomation (latrodectism) with black widow spider (BWS) venom can cause dysfunction in the cardiovascular system. The pathophysiology and consequences of cardiovascular effects have not been fully elucidated. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Of 364 initial results, 22 articles (20 case reports and two case series) were used with 25 patients in total. Seventeen (68%) patients had hypertension, and 16 (64%) had tachycardia. High troponin levels were found in 16 (64%) patients. Electrocardiographic changes consisted of nine (36%) patients with ST-T segment abnormalities and three (12%) patients with supraventricular tachyarrhythmias. Wall motion abnormalities were present in 11 (44%) patients, with three of the patients experiencing left ventricle global hypokinesis. A reduced ejection fraction was present in 10 (40%) patients. Only six (24%) patients received antivenom and were discharged with no further complications. In conclusion, raising awareness for cardiovascular complications could be useful as there are no pathognomonic features in imaging or electrocardiogram (ECG). The impact of antivenom on cardiovascular complications has not been prospectively studied., Competing Interests: Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Khakh et al.)

Spiders commonly disperse on silk lines as juveniles by means of rappelling or ballooning. These modes of dispersal, especially long‐distance dispersal via ballooning, can greatly increase the distance an individual can move and, at the population level, the speed of range expansion and likelihood of gene flow. Nevertheless, few studies have examined how spiders disperse under field conditions, and which environmental and meteorological conditions may affect their decision to disperse. We tested dispersal by spiderlings of the invasive brown widow (Latrodectus geometricus) under field conditions in the Negev Desert of Israel. We documented pre‐dispersal (climbing and tiptoeing) and dispersal (short‐distance dispersal by rappelling and long‐distance dispersal by ballooning) behaviours during the day (n = 147 spiders) and night (n = 171 spiders), while recording wind speed, temperature and humidity. We found that spiders ballooned significantly more during the day (14.3%) compared with 1.8% of spiders ballooning at night. At night, spiders were more likely to disperse in conditions of higher wind speeds, lower temperature and higher humidity, whereas during the day, environmental factors were less predictive of dispersal behaviour. In addition, we found significant differences in the proportion of spiderlings showing pre‐dispersal and dispersal behaviour depending on family line. In conjunction with human‐mediated dispersal, ballooning and rappelling may be an important mechanism of range expansion in the brown widow spider. Understanding the environmental and genetic factors affecting dispersal may lead to better management of invasive species. [ABSTRACT FROM AUTHOR]

Black widow spiders (Latrodectus sp.) are distributed worldwide, and in Albania the L. tredecimguttatus Rossi, 1790 has been the dominant spider. Other medically important spiders in Albania include the brown recluse with symptoms known as loxoscelism, the false black widow and the egg sac spiders; the last two inducing similar symptoms to a wasp sting. Methods: The data analyzed is from a decade-long study of 125 patients hospitalized in the regional hospital of Fier County, in the Western Lowland of Albania from May 2009 and to October 2018. Objective: Although the venom is rarely fatal, the recent spider bites raise questions about the influence of higher air temperatures on their possibly increased toxicity. Results: Significantly the severity of the α-latrotoxin rises during the summer, when human–spider contact frequency is higher and when the black widow spiders have an increased motivation to protect their egg sacs. Conclusion: This study revealed an increased severity of the black widow bites with respect to patient health, shown via all the severe systemic symptoms, during those months with higher temperatures.

Theory and empirical work suggest that behaviours such as dispersal and exploration are predictors of invasive success, and that behaviours may shift predictably after invasive populations have established and spread. However, there are limited data on temporal patterns in the distribution of behavioural traits linked to the timeline of establishment of invasive species. We examined dispersal and exploration, along with life history traits that may be linked to behaviour, across multiple invasive populations of the brown widow spider, Latrodectus geometricus. This global invader has established populations across the United States and Israel. Using this temporal and spatial variation, we tested predictions about changes in suites of traits over establishment time. We compared trait distributions of four U.S. populations of L. geometricus to patterns in four populations in Israel. We predicted that selective filters during the invasion process would result in more dispersive, more exploratory spiders that are larger and more fecund in recently established populations, but, if trade-offs occur, dispersal would be favoured at the expense of fecundity and size in recent populations. We found more frequent and faster dispersal in more recently established populations in Israel, but not the United States. Spiders in more recently established populations in Israel were larger than those in older populations, but there were no consistent patterns across U.S. populations. However, there was evidence in both the U.S. and Israel for differing trade-offs among fecundity, dispersal and size. In more recently established populations, spiders were more variable in resource allocation to eggsacs. The results suggest that in some populations, trade-offs underlying dispersal, fecundity and body size are shaped by the time interval, and thus the number of generations, since establishment, with implications for the role of evolutionary processes in invasion success. • Dispersal was more frequent and faster in recent invasive populations in Israel. • Spiders in more recently established populations in Israel were larger. • Trade-offs underlying dispersal are shaped by the time since invasion. [ABSTRACT FROM AUTHOR]

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.

In this paper, 319 incidents of snake predation by spiders are reported based on a comprehensive global literature and social media survey. Snake-catching spiders have been documented from all continents except Antarctica. Snake predation by spiders has been most frequently documented in USA (51% of all incidents) and Australia (29%). The captured snakes are predominantly small-sized with an average body length of 25.9 ± 1.3 cm (median = 27 cm; range: 5.8-100 cm). Altogether >90 snake species from seven families have been documented to be captured by >40 spider species from 11 families. About 60% of the reported incidents were attributable to theridiids (≈0.6-1.1 cm body length), a spider family that uses strong tangle webs for prey capture. Especially the Australian redback spider (Latrodectus hasselti Thorell, 1870), the African button spider (Latrodectus indistinctus O. Pickard-Cambridge, 1904), an Israeli widow spider (Latrodectus revivensis Shulov, 1948), and four species of North American widow spiders (Latrodectus geometricus C.L. Koch, 1841, Latrodectus hesperus Chamberlin & Ivie, 1935, Latrodectus mactans (Fabricius, 1775), and Latrodectus variolus Walckenaer, 1837) - equipped with a very potent vertebrate-specific toxin (α-latrotoxin) - have proven to be expert snake catchers. The use of vertebrates as a supplementary food source by spiders represents an opportunity to enlarge their food base, resulting in enhanced survival capability. Interestingly, the snakes captured by spiders also encompasses some species from the families Elapidae and Viperidae known to be highly toxic to humans and other vertebrates. Not only do spiders sometimes capture and kill snakes, quite often the tables are turned - that is, a larger number of arthropod-eating snake species (in particular nonvenomous species in the family Colubridae) include spiders in their diets. [ABSTRACT FROM AUTHOR]

Black widow spiders (Latrodectus spp.) are generally perceived as inhabiting southern or western United States. However, some species, such as the northern black widow, Latrodectus variolus , are also found in more temperate regions of USA and adjacent Canada. This species also appears to expand its range northward with the climate change increasing the risk of human encounters. To our knowledge, this is the first case report of a pediatric envenomation from a northern black widow bite in northeastern US. Medical practitioners often fail to recognize the signs and symptoms of latrodectism delaying effective treatment. Even in more northern locales, healthcare workers should take black widow spider envenomation under consideration in the differential diagnosis particularly with suspected exposure. [Display omitted] • The northern black widow spider (Latrodectus variolus) has an increasing presence in northeastern US. • Northern black widow spider bites cause symptoms similar to other black widow spiders of the Latrodectus species. • Healthcare workers should consider black widow spider envenomation in the differential diagnosis in more northern locales. • Latrodectism is most often diagnosed clinically and can be an elusive diagnosis. [ABSTRACT FROM AUTHOR]

Desarrollo ontogénico de Latrodectus sp. (grupo de mactamas) de Sierra de la Ventana. Las hembras que fueron recolectadas durante el verano, hicieron capullos en el laboratorio. Las arañas se han criado desde huevo hasta la etapa adulta. Se describe la longitud de cada estadio larvario y ninfal y los cambios ocurridos durante el desarrollo. Los principales hallazgos fueron: 1) Hay 3 etapas post-embrionarias. 2) Los machos alcanzaron la etapa adulta con 6 a 8 mudas (media 7) y las hembras con 9 a 11 mudas (media 10).

Latrodectus envenomations are common throughout the United States and the world. While many envenomations can result in catecholamine release with resultant hypertension and tachycardia, myocarditis is very rare. We describe a case of a 22- year-old male who sustained a Latrodectus envenomation complicated by cardiomyopathy. [West J Emerg Med. 2010; 11(5):521-523.]

Latrodectism is a rare, but potentially severe, clinical syndrome caused by spider of the genus Latrodectus. L. tredecimguttatus is widespread in Italy and its bite cause the injection of α-latrotoxin that cause depletion of acetylcholine at motor nerve endings and release of catecholamines at adrenergic nerve endings. We describe the first clinical case of L. tredecimguttatus poisoning successfully treated with L. mactans antivenom from North America. A healthy 60-year-old patient was admitted to the emergency department after unknown insect sting or arachnid/snake bite. In the early morning, the patient was working in the countryside when he felt a sting-like pain in the medial area of the right lower leg, associated with an intense burning sensation. An hour later he developed agitation, hoarseness, sweating, abdominal distress and intense pain in his right leg. In the emergency room vital signs showed a hypertensive crisis, tachycardia and peripheral oxygen desaturation. ECG was normal and ABE showed mixed acid-base disorder. Blood tests showed leukocytosis with neutrophilia, high levels of myoglobin, with normal coagulation and normal plasmatic cholinesterase. Neck, thorax and abdomen CT scan, with and without contrast medium, was negative. Four hours after admission hypertension worsened with board like rigid abdomen and onset of fasciculations, tremors, miosis and intense regional sweating. The definitive diagnosis of poisoning by L tredecimguttatus was based on the clinical picture. Within short time the antidote was provided by the Poison Centre and administered. A marked improvement of the symptomatology was noted after 30 minutes, and 1 hour later all symptoms were under control. The patient was discharged after 2 days. The clinical presentation of a patient suffering from latrodectism places the clinician in front of a challenging differential diagnosis. Following the suspicion, the first-line doctor is invited to discuss the case with a toxicologist, in order to confirm or exclude the diagnosis and implement all therapeutic measures. In our clinical case, the absence of organic lesions, laboratory tests not suggestive for other causes, and the presence of typical clinical feature suggested the diagnosis of L tredecimguttatus poisoning. This hypothesis was then supported by the close temporal relation between antivenom administration and symptoms improvement. With this case, we report the first use of L mactans antivenom from North America to treat L. tredecimguttatus poisoning and we confirm its effectiveness in counteracting latrodectism caused by this spider. • Latrodectism is a clinical syndrome caused by spider of genus latrodectus. • In Italy L. tredecimguttatus bite may cause severe clinical feature mainly in children or the elderly. • Latrodectism should be suspected when there is a specific clinical picture expecially in patients coming from the countryside. • Specific antidote is not available in Italy, at the present time. • The use of the antidote rise against Latrodectus mactans has been effective in this clinical case. [ABSTRACT FROM AUTHOR]

A spider's web is an extended phenotype and a direct product of behavior. Variation in web architecture may be the result of individual differences in genotype, environment, or experience. We analyzed variation in the web architecture of western black widow spiders, Latrodectus hesperus, by testing two hypotheses: (a) intrinsic individual differences and (b) plasticity according to experience of the site of prey capture. We used treatments manipulating the site of prey capture experienced by the spiders: sheet only, gum‐footed lines only, and alternating patterns between sheet and gum‐footed lines equally. We found considerable consistent individual variation (repeatability of r =.56) in one web component (gum‐footed lines) and negligible plasticity in either component. We discuss our results in terms of the potential for the design of these web components to respond to selection, and of potential additional causes of variation in extended phenotypes. [ABSTRACT FROM AUTHOR]

Risks of sociality, including competition and conspecific aggression, are particularly pronounced in venomous invertebrates such as arachnids. Spiders show a wide range of sociality, with differing levels of cannibalism and other types of social aggression. To have the greatest chance of surviving interactions with conspecifics, spiders must learn to assess and respond to risk. One of the major ways risk assessment is studied in spiders is via venom metering, in which spiders choose how much venom to use based on prey and predator characteristics. While venom metering in response to prey acquisition and predator defense is well-studied, less is known about its use in conspecific interactions. Here we argue that due to the wide range of both sociality and venom found in spiders, they are poised to be an excellent system for testing questions regarding whether and how venom use relates to the evolution of social behavior and, in return, whether social behavior influences venom use and evolution. We focus primarily on the widow spiders, Latrodectus, as a strong model for testing these hypotheses. Given that successful responses to risk are vital for maintaining sociality, comparative analysis of spider taxa in which venom metering and sociality vary can provide valuable insights into the evolution and maintenance of social behavior under risk.

Population-level trait variation within species plays an often-overlooked role in interspecific interactions. In this study, we compared among-individual variation in web phenotype and foraging behavior between native black widows (Latrodectus hesperus) and invasive brown widows (Latrodectus geometricus). We staged repeated contests whereby native widows defended their webs against intruders of both species to 1) investigate how trait variation mediates web contest outcome among native widows and 2) see whether widow behavior differs in response to an invasive spider. In only one trait, the average number of foraging lines, did black widows differ from brown widows. Black widow residents that built more structural lines were more likely to successfully defend their webs from conspecific intruders (i.e., be the sole spider remaining on the web postinteraction). This association between web structure and contest outcome did not exist in trials between black widows and invasive brown widows; however, in interspecific interactions, these same residents were more likely to have intruders remain on the web rather than drive them away. Surprisingly, brown widows did not usurp black widows. Brown widows were never observed signaling, yet black widow residents signaled equally to intruders of both species. Our results suggest that among-individual variation among native species can influence the response toward invasive competitors and outcome of these interactions. [ABSTRACT FROM AUTHOR]

Understanding patterns of diversity in sexual signals can give insight into processes initiating, mediating or following from species diversification. Here we focus on female sex pheromones, which are widespread among animals, where some taxa show phylogenetic patterns of variation, but for others, ecological factors better explain pheromone diversity. Causes of differences in these patterns are unclear, and general insights require studying a broader range of taxa. Here we examined variation in the responses of male redback spiders, Latrodectus hasselti , to sex pheromones produced by three allopatric female congeners with different degrees of phylogenetic relatedness (from the same clade: Latrodectus mirabilis, Latrodectus hesperus ; and from a different clade: Latrodectus geometricus) to infer pheromone divergence. We examined variation in male responses to conspecific and heterospecific females' airborne and contact pheromones, which attract males and elicit courtship behaviour, respectively. We measured male courtship responses to extracted contact pheromones in isolation and male preferences in response to airborne pheromones and combined cues (pheromones, silk) in a two-choice maze. Male responses to airborne chemicals, contact chemicals and combined cues suggested variation in species specificity, with L. hasselti males showing strong discrimination against airborne pheromones of L. hesperus females (same clade), moderate evidence for discrimination based on contact cues of L. geometricus , but only when multiple sources of information were available (different clade) , and no discrimination of L. mirabilis females (same clade) relative to conspecifics, regardless of the types of information available. Thus, male responses were not consistent with a phylogenetic pattern. Moreover, airborne pheromones can apparently diverge relatively rapidly, but airborne and contact pheromones may remain similar across long evolutionary timescales. We propose that differential responses to L. hesperus may arise from selection for population-level pheromone divergence within that species and that, in general, pheromones and male responses may be evolutionarily conserved across Latrodectus. • Airborne components less conserved than contact pheromones in the Latrodectus genus. • Pheromones alone are insufficient for accurate conspecific discrimination by males. • Male responses were not consistent with a phylogenetic pattern of diversification. • Variation in selection within species could be driving patterns of diversification. [ABSTRACT FROM AUTHOR]

Background: Black widow spider (Latrodectus spp) envenomation represents the most medically significant spider envenomation in the United States, prompting more than 2500 calls to poison centers annually. The female spider, which is responsible for symptomatic envenomations, is classically described as a shiny black spider with a red hourglass-shaped marking on the ventral abdomen. Clinical features of envenomation include painful muscle cramping, abdominal pain, and autonomic disturbances, such as tachycardia, hypertension, and diaphoresis. "Latrodectus facies" or "facies latrodectismica" is an additional distinctive but rarely described clinical finding characterized by periorbital edema, lacrimation, and blepharospasm.Case Report: A 6-year-old female developed the typical clinical features of Latrodectus envenomation after being found in bed with a Western black widow spider (Latrodectus hesperus) with no ventral marking. She initially improved with opioid analgesia, but 6 h later her symptoms worsened again, and concurrent with this worsening she developed Latrodectus facies. She received additional opioid analgesia and all her symptoms resolved within 24 h. Her mother provided informed and written consent for the acquisition and publication of the facial photographs presented. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: A high degree of clinical suspicion is necessary to correctly diagnose Latrodectus envenomation, especially when the spider escapes unnoticed or in young children in whom the bite is not witnessed. To our knowledge, Latrodectus facies has not been reported previously in a young child, and recognition of this finding will aid clinicians in limiting unnecessary interventions and administering appropriate therapy. [ABSTRACT FROM AUTHOR]

• Species distribution predictions are often biased towards a particular life stage. • We explored if CT Max of widow spiders differed by life stage, sex, and species. • We found that CT Max diminished from spiderlings to adults. • CT Max did not broadly differ between sexes and species of widows. Temperature strongly influences the physiology and behavior of ectotherms. Persistence within different environments can be limited by thermal tolerances. These thermal tolerances can also shift through life stages and differ between sexes. The critical thermal maximum (CT Max) defines the temperature at which animals experience unorganized locomotion or spasms. In this study, we tested if CT Max varied between a native and an invasive widow species. We separately tested if CT Max varied by widow life stage and sex. We predicted that the invasive species would have higher CT Max due to originally inhabiting warmer climates. We also predicted that juveniles and male widows would possess higher CT Max because they are more mobile and could experience a greater scope of thermal extremes throughout landscapes. We did not find a difference in CT Max between the species, but we did find differences across development stages. Temperature of spasms and death decreased with developmental stages, which corresponds with previous studies in spiders. Future studies of ontogenic and interspecific comparisons will be crucial for more broadly understanding how upper tolerances shapes species persistence in changing climates or ability to invade new habitats. [ABSTRACT FROM AUTHOR]

Introduction: Spiders are poisonous arthropods, and their accident is called "Arachnidism," which in our territory is produced mainly by the Loxoceles, Latrodectus, and Phoneutria genera. There are other spiders with a lower clinical risk. Objective: This article aims to contextualize the reader on the impact of these poisonous animals on Colombian people's health from the clinical-epidemiological perspective, assessing concepts and presenting theoretical foundations. Methodology: was reviewed 117 articles during the period between February 2019 and June 2020, using the Medline, Scopus, Bione, Ebsco, Lilacs, Pubmed, Science Direct, Scielo, and Web of Science databases. There are also presented two cases, one in La Mesa, Cundinamarca, and another in Sincelejo, Sucre. Conclusions: It is concluded that spiders of clinical - epidemiological importance are widely distributed in the national territory, being those with the most significant impact Phoneutria, Latrodectus, and Loxoceles, the latter being one that causes the most significant effects on human and animal populations in the country. [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 72 h. Methods: Two groups were selected, each one contained 6 male New Zealand rabbits weighing 2±0.5 kg. The ani­mals were anesthetized with 0.5 ml ketamine and 0.5 ml xylazine by intramuscular route. The L. dahli venom (0.5 mg/kg) was injected subcutaneously to both the groups. The second group of rabbits 24 h 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, 24 h 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 spe­cific-Latrodectus antivenin.

Through examination of specimens collected in 12 locations confirmed the presence of the genus Latrodectus distinguishing six morphotypes in six departments and four ecoregions of Bolivia. The results imply that there is a risk of accidents caused by the bite of these spiders.

AbstractThe article provides a historical report on venomous spider identification, venom obtainment methods and serum production at the Butantan Institute, São Paulo, Brazil. It is based on literature and personnal experience during the last 50 years. This result is the discovery that the real species causing potential severe human accidents were the spiders of the genus Loxosceles and Phoneutria.

The widow spider, Latrodectus, (Araneae: Theridiidae) comprise about 31 currently recognized species, some species are very hard to distinct; in this study morphological and molecular method has been used to confirm the diagnosis of the spiders. Phylogenetic tree was constructed using the neighbor-joining of some other Latrodectus sp. sampled, including taxa occurring in the Middle East, Australia, New Zealand, North and South America and Europe, and with the two genera Steatoda Sundevall, 1833 and Asagena Sundevall, 1833 outgroup. The results of the analysis show the highest identity (90%) for Latrodectus thoracicus Nicolet 1849 represented by three specimens and for L. pallidus O.P.-Cambridge, 1872 represented by one specimen in addition to (85%) for the false widow Asagena phalerata (Panzer, 1801) represented by one specimen, these three species is recorded in Iraq for the first time. [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]

Although aspects of an individual's state are well-known to influence the expression of behavior, it is still unclear how elements of state affect consistent among-individual differences in behavior. With binary, irreversible elements of state, such as mating status, there may be optimal behavioral phenotypes before and after mating, with individuals often prioritizing mate acquisition before and resource acquisition after. Yet, limited plasticity may prevent optimal behavior in both contexts. Additionally, it remains largely unknown if some consistencies in neural or physiological traits may limit the ability of the organism to respond to state changes. In this study, we investigated how changes in a binary state variable, mating status, affected both the mean expression and among-individual variation in behavior and web structure of the redback spider, Latrodectus hasselti. Furthermore, we explored the role of biogenic amines in potentially mediating individual differences in behavior and web structure. We found that mated females were overall more aggressive than virgin females and also built webs structured primarily for capturing prey rather than safety. We also found that individual differences in behavior and web structure were maintained across mating statuses, which indicates the stability of these traits and may drive personality-specific state-dependent fitness trade-offs. Finally, we found that aggressive spiders had higher central nervous system dopamine levels. Interestingly, web structure was often correlated with a catabolite of tyramine ( N-acetyltyramine), suggesting that variation in amine catabolism, and not the concentrations of the amines themselves, may drive individual differences in some traits. Significance statement: Our results demonstrate that although individuals show plasticity in response to changes in state, specifically mating status, individuals also maintain among-individual differences across this state change. Thus, aggressive individuals before mating will tend to be aggressive after. This maintenance of individual differences across state may drive differential fitness benefits before and after mating for different behavioral phenotypes. Furthermore, we show that biogenic amines and their catabolites are related to individual differences, thus identifying a potential mechanism underlying consistent variation. [ABSTRACT FROM AUTHOR]

“Black widow” spiders belong to the genus Latrodectus and are one of the few spiders in the world whose bite can cause severe envenomation in humans and domestic animals. In Argentina, these spiders are distributed throughout the country and are responsible for the highest number of bites by spiders of toxicological sanitary interest. Here, we studied the toxicity and some biochemical and immunochemical characteristics of eighteen venom samples from Latrodectus spiders from eight different provinces of Argentina, and the neutralization of some of these samples by two therapeutic antivenoms used in the country for the treatment of envenomation and by a anti- Latrodectus antivenom prepared against the venom of Latrodectus mactans from Mexico. We observed important toxicity in all the samples studied and a variation in the toxicity of samples, even in those from the same region and province and even in the same Latrodectus species from the same region. The therapeutic antivenoms efficiently neutralized all the venoms studied. [ABSTRACT FROM AUTHOR]

Background: Orb-web weaving spiders and their relatives use multiple types of task-specific silks. The majority of spider silk studies have focused on the ultra-tough dragline silk synthesized in major ampullate glands, but other silk types have impressive material properties. For instance, minor ampullate silks of orb-web weaving spiders are as tough as draglines, due to their higher extensibility despite lower strength. Differences in material properties between silk types result from differences in their component proteins, particularly members of the spidroin (spider fibroin) gene family. However, the extent to which variation in material properties within a single silk type can be explained by variation in spidroin sequences is unknown. Here, we compare the minor ampullate spidroins (MiSp) of orb-weavers and cobweb weavers. Orb-web weavers use minor ampullate silk to form the auxiliary spiral of the orb-web while cobweb weavers use it to wrap prey, suggesting that selection pressures on minor ampullate spidroins (MiSp) may differ between the two groups. Results: We report complete or nearly complete MiSp sequences from five cobweb weaving spider species and measure material properties of minor ampullate silks in a subset of these species. We also compare MiSp sequences and silk properties of our cobweb weavers to published data for orb-web weavers. We demonstrate that all our cobweb weavers possess multiple MiSp loci and that one locus is more highly expressed in at least two species. We also find that the proportion of ß-spiral-forming amino acid motifs in MiSp positively correlates with minor ampullate silk extensibility across orb-web and cobweb weavers. Conclusions: MiSp sequences vary dramatically within and among spider species, and have likely been subject to multiple rounds of gene duplication and concerted evolution, which have contributed to the diverse material properties of minor ampullate silks. Our sequences also provide templates for recombinant silk proteins with tailored properties. [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]

Background: Black widow spiders are infamous for their neurotoxic venom, which can cause extreme and longlasting pain. This unusual venom is dominated by latrotoxins and latrodectins, two protein families virtually unknown outside of the black widow genus Latrodectus, that are difficult to study given the paucity of spider genomes. Using tissue-, sex- and stage-specific expression data, we analyzed the recently sequenced genome of the house spider (Parasteatoda tepidariorum), a close relative of black widows, to investigate latrotoxin and latrodectin diversity, expression and evolution. Results: We discovered at least 47 latrotoxin genes in the house spider genome, many of which are tandem-arrayed. Latrotoxins vary extensively in predicted structural domains and expression, implying their significant functional diversification. Phylogenetic analyses show latrotoxins have substantially duplicated after the Latrodectus/Parasteatoda split and that they are also related to proteins found in endosymbiotic bacteria. Latrodectin genes are less numerous than latrotoxins, but analyses show their recruitment for venom function from neuropeptide hormone genes following duplication, inversion and domain truncation. While latrodectins and other peptides are highly expressed in house spider and black widow venom glands, latrotoxins account for a far smaller percentage of house spider venom gland expression. Conclusions: The house spider genome sequence provides novel insights into the evolution of venom toxins once considered unique to black widows. Our results greatly expand the size of the latrotoxin gene family, reinforce its narrow phylogenetic distribution, and provide additional evidence for the lateral transfer of latrotoxins between spiders and bacterial endosymbionts. Moreover, we strengthen the evidence for the evolution of latrodectin venom genes from the ecdysozoan Ion Transport Peptide (ITP)/Crustacean Hyperglycemic Hormone (CHH) neuropeptide superfamily. The lower expression of latrotoxins in house spiders relative to black widows, along with the absence of a vertebratetargeting α-latrotoxin gene in the house spider genome, may account for the extreme potency of black widow venom. [ABSTRACT FROM AUTHOR]

The genus Latrodectus has not been studied in Colombia even though it is medically important worldwide; there are three species for the country, this study focused on a non-identified species found in the Tatacoa Desert in the Huila Department. This research is the first approximation to the extraction, composition analysis and toxicity evaluation of the venom of a species of the genus Latrodectus in Colombia; and aims to evaluate the toxicity by the initial characterization of its venom. The venom extraction was accomplished with electrostimulation and total protein concentration was determined by the Lowry method and BCA assays from crude venom; with these methods, high protein concentration of the samples was measured. Bioassays on mice were also made to evaluate the toxicity and compare the symptoms produced by this Colombian spider to the Latrodectism Syndrome. Finally, an SDS-PAGE electrophoresis was used to separate the main components of high molecular weight from the samples and compared to a control of the venom of Latrodectus mactans to determine if the venom composition is different between these two species. [ABSTRACT FROM AUTHOR]

The iconic red hourglass of the black widow spiders (genus Latrodectus) is traditionally considered an aposematic signal, yet experimental evidence is lacking. Here, we present data that suggest that black widow coloration may have evolved to be an aposematic signal that is more conspicuous to their vertebrate predators than to their insect prey. In choice experiments with wild birds, we found that the red-and-black coloration deters potential predators: Wild birds were ~3 times less likely to attack a black widow model with an hourglass than one without. Using visual-system appropriate models, we also found that a black widow's red-and-black color combo is more apparent to a typical bird than a typical insect. Additionally, an ancestral reconstruction reveals that red dorsal coloration is ancestral in black widows and that at some point some North American widows lost their red dorsal coloration. Behaviorally, differences in red dorsal coloration between 2 North American species are accompanied by differences in microhabitat that affects how often a bird will view a black widow's dorsal region. All observations are consistent with a cost–benefit trade-off of being more conspicuous to predators than to prey. We suggest that limiting detection by prey may help explain why red and black aposematic signals occur frequently in nature. [ABSTRACT FROM AUTHOR]