Latrodectus Hesperus Research Articles

Black widow spiders,Latrodectusspp. (Araneae: Theridiidae), and other spiders feeding on mammals

A survey of reports on spiders preying on small, non-flying mammals (i.e., mice, deer mice, voles, rats, heteromyid rodents, shrews) published in the literature and in the social media yielded a total of 42 naturally occurring incidents. Spiders from five families (Agelenidae, Ctenidae, Sparassidae, Theraphosidae, and Theridiidae) were reported capturing small mammals under natural conditions. Additionally, spiders from four more families (Atracidae, Lycosidae, Pisauridae, and Porrhothelidae) are known to kill small mammals in captivity. Approximately 80% of the reported incidents were attributable to theridiid spiders, especially the Australian redback spider (Latrodectus hasselti Thorell, 1870) and three species of North American widow spiders (Latrodectus geometricus C.L. Koch, 1841, Latrodectus hesperus Chamberlin & Ivie, 1935, and Latrodectus mactans (Fabricius, 1775)) that have been shown to be expert mouse-catchers. The success of widow spiders in subduing small mammals can be explained by their ability to spin strong webs made up of tough silk, and producing a very potent toxin (α-latrotoxin) specifically targeting the vertebrate nervous system.

Extraordinary Mechanical Properties of Composite Silk Through Hereditable Transgenic Silkworm Expressing Recombinant Major Ampullate Spidroin

Spider dragline silk is a remarkable material that shows excellent mechanical properties, diverse applications, biocompatibility and biodegradability. Transgenic silkworm technology was used to obtain four types of chimeric silkworm/spider (termed composite) silk fibres, including different lengths of recombinant Major ampullate Spidroin1 (re-MaSp1) or recombinant Major ampullate Spidroin2 (re-MaSp2) from the black widow spider, Latrodectus hesperus. The results showed that the overall mechanical properties of composite silk fibres improved as the re-MaSp1 chain length increased, and there were significant linear relationships between the mechanical properties and the re-MaSp1 chain length (p < 0.01). Additionally, a stronger tensile strength was observed for the composite silk fibres that included re-MaSp1, which only contained one type of repetitive motif, (GA)n/An, to provide tensile strength, compared with the silk fibres that includedre-MaSp2, which has the same protein chain length as re-MaSp1 but contains multiple types of repetitive motifs, GPGXX and (GA)n/An. Therefore, the results indicated that the nature of various repetitive motifs in the primary structure played an important role in imparting excellent mechanical properties to the protein-based silk fibres. A silk protein with a single type of repetitive motif and sufficiently long chains was determined to be an additional indispensable factor. Thus, this study forms a foundation for designing and optimizing the structure of re-silk protein using a heterologous expression system.

Urban hubs of connectivity: contrasting patterns of gene flow within and among cities in the western black widow spider.

As urbanization drastically alters the natural landscape and generates novel habitats within cities, the potential for changes to gene flow for urban-dwelling species increases. The western black widow spider (Latrodectus hesperus) is a medically relevant urban adapter pest species, for which we have previously identified population genetic signatures consistent with urbanization facilitating gene flow, likely due to human-mediated transport. Here, in an analysis of 1.9 million genome-wide SNPs, we contrast broad-scale geographical analyses of 10 urban and 11 non-urban locales with fine-scale within-city analyses including 30 urban locales across the western USA. These hierarchical datasets enable us to test hypotheses of how urbanization impacts multiple urban cities and their genetic connectivity at different spatial scales. Coupled fine-scale and broad-scale analyses reveal contrasting patterns of high and low genetic differentiation among locales within cities as a result of low and high genetic connectivity, respectively, of these cities to the overall population network. We discuss these results as they challenge the use of cities as replicates of urban eco-evolution, and have implications for conservation and human health in a rapidly growing urban habitat.

Urbanization as a facilitator of gene flow in a human health pest.

Urban fragmentation can reduce gene flow that isolates populations, reduces genetic diversity and increases population differentiation, all of which have negative conservation implications. Alternatively, gene flow may actually be increased among urban areas consistent with an urban facilitation model. In fact, urban adapter pests are able to thrive in the urban environment and may be experiencing human-mediated transport. Here, we used social network theory with a population genetic approach to investigate the impact of urbanization on genetic connectivity in the Western black widow spider, as an urban pest model of human health concern. We collected genomewide single nucleotide polymorphism variation from mitochondrial and nuclear double-digest RAD (ddRAD) sequence data sets from 210 individuals sampled from 11 urban and 10 nonurban locales across its distribution of the Western United States. From urban and nonurban contrasts of population, phylogenetic, and network analyses, urban locales have higher within-population genetic diversity, lower between-population genetic differentiation and higher estimates of genetic connectivity. Social network analyses show that urban locales not only have more connections, but can act as hubs that drive connectivity among nonurban locales, which show signatures of historical isolation. These results are consistent with an urban facilitation model of gene flow and demonstrate the importance of sampling multiple cities and markers to identify the role that urbanization has had on larger spatial scales. As the urban landscape continues to grow, this approach will help determine what factors influence the spread and adaptation of pests, like the venomous black widow spider, in building policies for human and biodiversity health.

Dissection of silk glands in the Western black widowLatrodectus hesperus

The silk glands of the Western black widow Latrodectus hesperus Chamberlin & Ivie, 1935 are morphologically and functionally distinct. Studies of spider silk glands often show only high magnification images of sections or drawings of glands, making differentiation of dissected glands difficult. We dissect all of the gland types from L. hesperus females and show their gross morphology with light microscopy. Our micrographs portray the distinct morphologies and relative sizes of each silk gland type, consistent with prior descriptions of the silk apparatus of Latrodectus spiders. Notably, we verify the presence of two differentiated pairs of aggregate silk glands and spigots, thus resolving a discrepancy in the literature.

Nuevos registros de arañas (Arachnida: Araneae) para México y listado actualizado de la araneofauna del estado de Coahuila

Se dan a conocer cuatro nuevos registros de especies de arañas para México (Herpyllus schwarzi, Nodocion rufithoracicus Phrurotimpus woodburyi y Thanatus altimontis) y cuatro registros nuevos para el estado de Coahuila (Euagrus chisoseus, Herpyllus propinquus, Latrodectus hesperus y Titanebo mexicanus). Se presenta un listado actualizado con 178 especies de arañas presentes en Coahuila, agrupadas en 100 géneros y 32 familias. Las familias con mayor número de especies fueron Gnaphosidae (39), Lycosidae (22) y Salticidae (15). El estado de Coahuila ocupa el doceavo lugar en la riqueza de arañas en México.

Conservation of folding and association within a family of spidroin N-terminal domains

Web spiders synthesize silk fibres, nature’s toughest biomaterial, through the controlled assembly of fibroin proteins, so-called spidroins. The highly conserved spidroin N-terminal domain (NTD) is a pH-driven self-assembly device that connects spidroins to super-molecules in fibres. The degree to which forces of self-assembly is conserved across spider glands and species is currently unknown because quantitative measures are missing. Here, we report the comparative investigation of spidroin NTDs originating from the major ampullate glands of the spider species Euprosthenops australis, Nephila clavipes, Latrodectus hesperus, and Latrodectus geometricus. We characterized equilibrium thermodynamics and kinetics of folding and self-association using dynamic light scattering, stopped-flow fluorescence and circular dichroism spectroscopy in combination with thermal and chemical denaturation experiments. We found cooperative two-state folding on a sub-millisecond time scale through a late transition state of all four domains. Stability was compromised by repulsive electrostatic forces originating from clustering of point charges on the NTD surface required for function. pH-driven dimerization proceeded with characteristic fast kinetics yielding high affinities. Results showed that energetics and kinetics of NTD self-assembly are highly conserved across spider species despite the different silk mechanical properties and web geometries they produce.

Postharvest fumigation of California table grapes with ozone to control Western black widow spider (Araneae: Theridiidae)

Ozone fumigations were evaluated for postharvest control of Western black widow spider (BWS), Latrodectus hesperus (Chamberlin and Ivie), in fresh table grapes destined for export from California USA. Mature adult female black widow spiders were contained in separate gas-permeable cages within a flow-through vacuum chamber and exposed for 1h at 3±1°C (x¯±s) and 67.5kPa to gaseous ozone at eight steady-state concentrations (i.e, [O3]ss) over the range 0.71±0.04–16.91±0.28gm−3 (x¯±s) (i.e., 500±25–12,000±200ppmv (μLL−1)) with or without supplementation of atmospheric carbon dioxide levels, respectively 129.3 or ca. 0.8gm−3 [CO2]ss (i.e., 100,000 or ca. 600ppmv). Regression models of the concentration-mortality response predict 98% mortality of adult female BWS populations following ozone fumigation for 1h at 3±1°C when headspace [O3]ss is maintained at ∼14gm−3 (i.e., 10,000ppmv) with ambient atmospheric CO2 levels ([CO2]ss=0.8gm−3). Providing evidence to support the use of these treatment parameters for control of BWS in packed table grapes, 0 survivors were observed from 268 total specimens treated in a series of confirmatory fumigations conducted for 1h at 3±1°C and 67.5kPa with headspace [O3]ss and [CO2]ss maintained ≥14 and ca. 0.8gm−3, respectively.

Silk gene expression of theridiid spiders: implications for male-specific silk use

Spiders (order Araneae) rely on their silks for essential tasks, such as dispersal, prey capture, and reproduction. Spider silks are largely composed of spidroins, members of a protein family that are synthesized in silk glands. As needed, silk stored in silk glands is extruded through spigots on the spinnerets. Nearly all studies of spider silks have been conducted on females; thus, little is known about male silk biology. To shed light on silk use by males, we compared silk gene expression profiles of mature males to those of females from three cob-web weaving species (Theridiidae). We de novo assembled species-specific male transcriptomes from Latrodectus hesperus, Latrodectus geometricus, and Steatoda grossa followed by differential gene expression analyses. Consistent with their complement of silk spigots, male theridiid spiders express appreciable amounts of aciniform, major ampullate, minor ampullate, and pyriform spidroin genes but not tubuliform spidroin genes. The relative expression levels of particular spidroin genes varied between sexes and species. Because mature males desert their prey-capture webs and become cursorial in their search for mates, we anticipated that major ampullate (dragline) spidroin genes would be the silk genes most highly expressed by males. Indeed, major ampullate spidroin genes had the highest expression in S. grossa males. However, minor ampullate spidroin genes were the most highly expressed spidroin genes in L. geometricus and L. hesperus males. Our expression profiling results suggest species-specific adaptive divergence of silk use by male theridiids.

Recombinant Production, Characterization, and Fiber Spinning of an Engineered Short Major Ampullate Spidroin (MaSp1s).

Spider dragline silk exhibits an extraordinary toughness and is typically composed of two types of major ampullate spidroins (MaSp1 and MaSp2), differing in their proline content and hydrophobicity. In this paper, we recombinantly produced an unusual but naturally occurring short major ampullate spidroin (MaSp1s) as a fusion construct between established Latrodectus hesperus terminal domains and the novel Cyrtophora moluccensis core domain. The sequence of the recombinant spidroin was engineered to guarantee high yields upon recombinant production and was named eMaSp1s. Its solution structure as well as the mechanical properties of wet-spun eMaSp1s fibers were examined. Structural characterization using CD- and FTIR spectroscopy showed a predominantly α-helical solution structure and a high ß-sheet content within fibers. Surprisingly, eMaSp1s fibers show similar mechanical properties as wet-spun fibers of other engineered spider silk proteins, albeit eMaSp1s has a lower molecular weight and not the typical sequence repeats in its core domain. Therefore, the findings provide insights into the molecular interplay necessary to obtain the typical silk fiber mechanics.

Life-history data for the funnel weavers Eratigena agrestis and Eratigena atrica (Araneae: Agelenidae) in the Pacific Northwest of North America

AbstractThe life history of the funnel weaver Eratigena agrestis (Walckenaer) (Araneae: Agelenidae) is not well studied despite its widespread occurrence in Europe and its establishment and spread in the Pacific Northwest of North America since its introduction in the early 20th century. We report phenology and life-history data for E. agrestis and another co-occurring funnel weaver, Eratigena atrica (Koch), in two study sites in British Columbia, Canada. The most notable difference in phenology between the two Eratigena species was the timing of emergence: E. atrica spiderlings emerge in the fall whereas E. agrestis spiderlings emerge in the spring. Surprisingly, the contrasting densities of E. atrica in the two study sites and the presence of the western black widow spider, Latrodectus hesperus Chamberlin and Ivie (Araneae: Theridiidae), in one study site had little effect on the life history of E. agrestis. This unexpected finding may be explained by (i) low overall competition pressure in the study habitats, (ii) conspecifics and heterospecifics exerting equivalent competition or predation pressures; and/or (iii) aggregations of heterospecifics providing benefits that offset costs associated with any competition.

Conformational Stability and Interplay of Helical N- and C-Terminal Domains with Implications on Major Ampullate Spidroin Assembly.

Major ampullate spidroin (MaSp) assembly starts in the abdomen of the spider, where spidroins are stored as a liquid dope at a high concentration. The dope is squeezed into the spinning duct, and assembly is finished upon drawing of fibers. Unwanted aggregation of the spidroin solution in the gland is suppressed by prestructuring of the spidroins in micelle-like assemblies, with their hydrophobic stretches being hidden from the solvent and the hydrophilic nonrepetitive amino (NRN) and carboxy (NRC) terminal domains being exposed on the micelle surface. Conversion of the fluid dope into a solid fiber is induced within the spinning duct by acidification and ion exchange (sodium chloride against potassium phosphate), with the impact on the structure of the NRN and NRC domains acting as a regulatory switch for fiber assembly. While NRN dimerizes pH-dependently in an antiparallel fashion (i.e. quaternary structural changes), the tertiary structure of dimeric NRC is changed by shear stress and a drop in pH, inducing the alignment of the intrinsically unstructured core domains accompanied by β-sheet formation of motifs of the core domain. Here, the conformational stability of NRN1 and NRC1 of Latrodectus hesperus MaSp1 were studied using independent techniques such as circular dichroism, fluorescence and absorbance spectroscopy, and scanning electron, transmission electron, and atomic force microscopy. In this context, it could be shown that strong, non-natural acidification drives NRC1 to unfold and aggregate into β-sheet-rich structures, preventing recombinant spidroins from assembling into aligned fibrils. Interestingly, NRN1 and NRC1 apparently do not interact with each other, making spidroin assembly easy to control step-by-step and straightforward due to missing unproductive side reactions.

WITHDRAWN: Neuropeptide evolution: Chelicerate neurohormone and neuropeptide genes may reflect one or more whole genome duplications

Four genomes and two transcriptomes from six Chelicerate species were analyzed for the presence of neuropeptide and neurohormone precursors and their GPCRs. The genome from the spider Stegodyphus mimosarum yielded 87 neuropeptide precursors and 101 neuropeptide GPCRs. High neuropeptide transcripts were also found in the trancriptomes of three other spiders, Latrodectus hesperus, Parasteatoda tepidariorum and Acanthoscurria geniculata. For the scorpion Mesobuthus martensii the numbers are 79 and 74 respectively. The very small genome of the house dust mite, Dermatophagoides farinae, on the other hand contains a much smaller number of such genes. A few new putative Arthropod neuropeptide genes were discovered. Thus, both spiders and the scorpion have an achatin gene and in spiders there are two different genes encoding myosuppressin-like peptides while spiders also have two genes encoding novel LGamides. Another finding is the presence of trissin in spiders and scorpions, while neuropeptide genes that seem to be orthologs of Lottia LFRYamide and Platynereis CCRFamide were also found. Such genes were also found in various insect species, but seem to be lacking from the Holometabola. The Chelicerate neuropeptide and neuropeptide GPCR genes often have paralogs. As the large majority of these are probably not due to local gene duplications, is not impossible that they reflect the effects of one or more ancient whole genome duplications.

Acidic Residues Control the Dimerization of the N-terminal Domain of Black Widow Spiders’ Major Ampullate Spidroin 1

Dragline silk is the most prominent amongst spider silks and comprises two types of major ampullate spidroins (MaSp) differing in their proline content. In the natural spinning process, the conversion of soluble MaSp into a tough fiber is, amongst other factors, triggered by dimerization and conformational switching of their helical amino-terminal domains (NRN). Both processes are induced by protonation of acidic residues upon acidification along the spinning duct. Here, the structure and monomer-dimer-equilibrium of the domain NRN1 of Latrodectus hesperus MaSp1 and variants thereof have been investigated, and the key residues for both could be identified. Changes in ionic composition and strength within the spinning duct enable electrostatic interactions between the acidic and basic pole of two monomers which prearrange into an antiparallel dimer. Upon naturally occurring acidification this dimer is stabilized by protonation of residue E114. A conformational change is independently triggered by protonation of clustered acidic residues (D39, E76, E81). Such step-by-step mechanism allows a controlled spidroin assembly in a pH- and salt sensitive manner, preventing premature aggregation of spider silk proteins in the gland and at the same time ensuring fast and efficient dimer formation and stabilization on demand in the spinning duct.

Developmental morphology of a lyriform organ in the Western black widow (Latrodectus hesperus)

For most spiders, their sensory world is dominated by their ability to detect vibrational stimuli. The organs responsible for detecting substrate vibrations are located on the animals’ extremities and known as lyriform organs, close aggregations of membrane-covered slits in the cuticular exoskeleton. The morphology and geometry of the lyriform organ is an important determinant of how it functions and the range of stimuli it can detect. Most work on the morphology, mechanics and physiology of lyriform organs has been conducted on adult wandering spiders, Cupiennius salei, and little is known about the morphology in other species or juveniles. We examine the morphology of the HS10 lyriform organ in both adult and juvenile Western black widows (Latrodectus hesperus). We find hypoallometric scaling of the lyriform organ and the size of individual slits when compared to body size. However, the cuticular pad distal to HS10 scales isometrically across successive instars. We also find an increase in the number of slits within the lyriform organ with each moult. Future work should address physiological responses of the organ across development, which could lead to a better understanding of the function of the cuticular pad and stimuli pertinent to the survival of little-studied juvenile spiders.

Extreme developmental synchrony reduces sibling cannibalism in the black widow spider, Latrodectus hesperus

Cannibalism, intraspecific predation, is a fascinating behaviour that can serve as a model system for researchers interested in learning more about conspecific conflicts ranging from siblicide to sexual cannibalism. Cannibalism is most often studied in terms of the benefits it provides the predator, but the prevalence of such an ecologically significant behaviour is also shaped by the costs inherent in a cannibalistic attack. Perhaps most intuitively, the risk of injury when attacking a conspecific of similar or larger size has been considered, and led to the prediction that cannibalism should be most common by larger individuals among asymmetrically sized pairs. This prediction is commonplace in the cannibalism literature, and leads to the more novel hypothesis that siblicide then may be reduced to the extent that maternal investment yields developmental synchrony and size-matched siblings. Here we test these hypotheses in the western black widow spider, Latrodectus hesperus , by rearing some eggs at 4 °C warmer temperatures for 7 days, and thus experimentally creating size asymmetries between clutchmates. Our temperature manipulation was successful at speeding development (eggs reared at warmer temperatures attained their first moult 2.5 days sooner than their counterparts). This developmental asynchrony accelerated cannibalism by more than 3 days relative to control groups in which eggs and spiderlings were all reared at either consistently colder or warmer temperatures. Lastly, the mass and size of an egg were poor predictors of cannibalism in both treatments that included individuals reared at warm temperatures. In contrast, in our control group where both eggs were reared at cooler temperatures, we found that families typified by heavier and larger eggs were slower to show cannibalistic behaviour. We discuss the implications of these findings, paying particular attention to their relevance to the black widow's emerging role as an urban pest.

Ontogeny of defensive behaviors in the western black widow spider (Latrodectus hesperus)

Ontogeny of defensive behaviors in the western black widow spider (Latrodectus hesperus)

Vibration transmission through sheet webs of hobo spiders (Eratigena agrestis) and tangle webs of western black widow spiders (Latrodectus hesperus)

Web-building spiders construct their own vibratory signaling environments. Web architecture should affect signal design, and vice versa, such that vibratory signals are transmitted with a minimum of attenuation and degradation. However, the web is the medium through which a spider senses both vibratory signals from courting males and cues produced by captured prey. Moreover, webs function not only in vibration transmission, but also in defense from predators and the elements. These multiple functions may impose conflicting selection pressures on web design. We investigated vibration transmission efficiency and accuracy through two web types with contrasting architectures: sheet webs of Eratigena agrestis (Agelenidae) and tangle webs of Latrodectus hesperus (Theridiidae). We measured vibration transmission efficiencies by playing frequency sweeps through webs with a piezoelectric vibrator and a loudspeaker, recording the resulting web vibrations at several locations on each web using a laser Doppler vibrometer. Transmission efficiencies through both web types were highly variable, with within-web variation greater than among-web variation. There was little difference in transmission efficiencies of longitudinal and transverse vibrations. The inconsistent transmission of specific frequencies through webs suggests that parameters other than frequency are most important in allowing these spiders to distinguish between vibrations of prey and courting males.

RETRACTED ARTICLE: Prolonged food restriction decreases body condition and reduces repeatability in personality traits in web-building spiders

Variation in state, which is any factor that alters the value of decision options, is likely one of the most common drivers of personality differences. However, the general relationship between individuals’ body state and various personality metrics/average behavioral type, repeatability of behavior, and behavioral syndrome structure is still poorly resolved. Here, we manipulate body condition in three spider species (Agelenopsis aperta, Latrodectus hesperus, and Anelosimus studiosus) using contrasting feeding schedules. We then assessed the effects of historic feeding regime on individuals’ body condition, boldness, and foraging aggressiveness. We further assessed the effects of feeding regimes on the repeatability of boldness and aggressiveness and the presence/absence of correlations between these two traits. We found that feeding treatment impacted individuals’ average boldness and aggressiveness in two species (A. aperta and A. studiosus). We also noted that among-individual variance in both boldness and aggressiveness was severely reduced when A. aperta and A. studiosus were subjected to prolonged food restriction, steeply reducing repeatability in these traits. Finally, we noted that correlations between boldness and foraging aggressiveness were detectable only in one case, revealing no compelling relationship between food restriction and the presence/absence of behavioral correlations. Taken together, our results suggest that food restriction has only weak, circumstantial effects on individuals’ average personality type and the correlations between behavioral traits. However, there appears to be a robust positive relationship between food availability and the signature of consistent individual differences in behavior. Under laboratory conditions, we found that lower feeding rates sharply decreased the repeatability of aggressiveness and boldness in two spider species. In doing so, we provide the second body of evidence suggesting that a highly prevalent and ecologically relevant state variable, higher body condition, can increase the repeatability of foraging-related behavioral traits. Additionally, under some feeding regimes, we found that hunger levels could alter the average individual aggressiveness and boldness but not correlations between these traits. This work highlights the importance of state variables such as hunger in eroding behavioral repeatability, the defining trait of personality.

The contribution of developmental experience vs. condition to life history, trait variation and individual differences.

1. Developmental experience, for example food abundance during juvenile stages, is known to affect life history and behaviour. However, the life history and behavioural consequences of developmental experience have rarely been studied in concert. As a result, it is still unclear whether developmental experience affects behaviour through changes in life history, or independently of it. 2. The effect of developmental experience on life history and behaviour may also be masked or affected by individual condition during adulthood. Thus, it is critical to tease apart the effects of developmental experience and current individual condition on life history and behaviour. 3. In this study, we manipulated food abundance during development in the western black widow spider, Latrodectus hesperus, by rearing spiders on either a restricted or ad lib diet. We separated developmental from condition-dependent effects by assaying adult foraging behaviour (tendency to attack prey and to stay on out of the refuge following an attack) and web structure multiple times under different levels of satiation following different developmental treatments. 4. Spiders reared under food restriction matured slower and at a smaller size than spiders reared in ad lib conditions. Spiders reared on a restricted diet were more aggressive towards prey and built webs structured for prey capture, while spiders reared on an ad lib diet were less aggressive and built safer webs. Developmental treatment affected which traits were plastic as adults: restricted spiders built safer webs when their adult condition increased, while ad lib spiders reduced their aggression when their adult condition increased. The amount of individual variation in behaviour and web structure varied with developmental treatment. Spiders reared on a restricted diet exhibited consistent variation in all aspects of foraging behaviour and web structure, while spiders reared on an ad lib diet exhibited consistent individual variation in aggression and web weight only. 5. Developmental experience affected the average life history, behaviour and web structure of spiders, but also shaped the amount of phenotypic variation observed among individuals. Surprisingly, developmental experience also determined the particular way in which individuals plastically adjusted their behaviour and web structure to changes in adult condition.