Biofluorescence has been reported in all extant chelicerate orders, but genus- or species-specific documentation remains limited. This gap is particularly noticeable in amblypygids (tailless whip spiders), where detailed descriptions of biofluorescence have not yet been fully developed. Here, we present the first description and photographic documentation of suspected biofluorescent patterns in Mesoamerican amblypygids. We collected two specimens, likely belonging to the genera Paraphrynus Moreno, 1940 and Phrynus Lamark, 1801, from an urban area on the Pacific coast of Guanacaste, Costa Rica. Under 365 nm light, these specimens appeared to display blue-green fluorescence at the joints and soft cuticle segments. Our findings suggest that further research is necessary to confirm the presence of fluorophores by using techniques such as spectrofluorimetry, to explore the ecological role of biofluorescence, and to describe biofluorescent patterns across amblypygid taxa.
Scorpions mainly feed on insects and other invertebrates. However, several species include small vertebrates in their diets. Here, we report a case of lizard consumption by a Mediterranean scorpion. This is the first documented case of Aegaeobuthus gibbosus (Brulle, 1832) (Buthidae) preying on the gecko Mediodactylus kotschyi, adding to a limited body of reports of lizard predation by European scorpions.
Polysphinctine wasps have evolved highly specialized life strategies that allow them to parasitize different spider hosts effectively. In this report, we document juvenile orchard orb-weavers Leucauge tessellata (Thorell, 1887) singly carrying larvae of a polysphinctine wasp from the Acrodactyla quadrisculpta-group. The wasp was identified using its morphological characteristics, mode of parasitism, and mt-COI phylogenetic analysis. Observations revealed that all three Acrodactyla sp. larvae collected were attached to the left mediolateral abdomen of the host spiders, where they consumed hemolymph until pupation. Before being killed by their parasitoids, host spiders exhibited modified web-building behavior, constructing a reduced cocoon web in place of the characteristic orb web of L. tessellata. Our PLS-PM analysis showed a significant negative correlation between the host spider's developmental stage and the parasitism rate (P = 0.02), which suggests that Acrodactyla sp. wasps selectively target juvenile L. tessellata, likely because they are less able to dislodge the larva from its attachment site compared to adult spiders. We speculate that the apparently consistent site of larval attachment in this specific spider-parasitoid interaction may represent a specific host-utilization adaptation in the observed Acrodactyla sp. wasps. Further investigation is warranted to strengthen evidence for our interpretation of this behavior and to explore its evolutionary implications.
Adult female spiders of the brown widow spider, Latrodectus geometricus CL Koch, 1841, lay multiple egg sacs during their lifetime, with each egg sac containing between 50 and 250 offspring. The mother supplements her developing embryos with additional lipids and proteins, and the spiderlings undergo one molt within the egg sac before emerging. Thereafter, the spiderlings may remain in the mother's web for up to several days, and then disperse and build their own webs and seek prey. Prey availability, however, is unpredictable, and may differ among habitats. For synanthropic spiders like L. geometricus, that live in close proximity with human dwellings, prey availability might vary considerably. Here, we compared mortality, growth and development of the brown widow spider, Latrodectus geometricus, from neonate to adult under two different prey availability regimes. Growth curves were plotted by weighing spiderlings fed weekly or every three weeks on fruit flies and then blow flies or crickets. Mortality rates were significantly higher when spiderlings received less prey, and only 7 spiderlings survived when fed intermittently, whereas of those fed weekly, approximately 60% reached adulthood. Males developed linearly, molted a mean of approximately 4 times, and attained maximum body masses after 100 days, whereas females developed exponentially, molted 8-9 times, and reached maximum body masses after 170 days. The growth rate of males was consistent across different instars whereas it was highest in later female instars. Mature males were less than 1% as large as mature females, revealing extreme sexual size dimorphism in this species.
The interaction of polysphinctine ectoparasitoids with their 2D-web-building spider hosts is characterized by alterations in web-building behavior, where the manipulated spider builds a so-called “cocoon web”, a unique structure that is important for pupal survival. Alteration of the web architecture of spider hosts building a 3D web has been observed only rarely. We documented interactions between the parasitoid Acrodactyla degener and the linyphiid sheet-web-building spider Mughiphantes mughi (Fickert, 1875), a new host from spruce stands in central Europe. When the parasitoid reached the final instar larva, the spider was killed and consumed on the underside of the sheet web (the typical spider position on the sheet web), after which the parasitoid larva produced a cocoon incorporated horizontally into the sheet of the web. We identified the reduction of some parts of the web of parasitized M. mughi, but the origin and the function of this reduction are not clear.
Courtship and mating behaviors are conspicuous and can attract eavesdroppers that pose a threat to both males and females. The body condition of females has significant effects on their reproductive output and so males should value well-fed females and be willing to take on increased risk in exchange for the opportunity to mate. We tested the hypothesis that predation risk affects male activity and mating behavior differently based on the female's body condition. We manipulated the body condition of female Pardosa milvina (Hentz, 1944) (Araneae: Lycosidae) and monitored the activity of males when placed on female substrate-borne cues with or without similar cues from their common predator, Tigrosa helluo (Walckenaer, 1837) (Araneae: Lycosidae). Males appeared to engage in a search for females on cues from well-fed females as they spent more time walking but covered less distance. Predator cues reduced this activity when coupled with cues from well-fed, but not food-limited females. In a second experiment, males were paired with females that differed in body condition and included treatments with and without predator risk. Females in good condition attacked males less and were more likely to mate. Males courted hungry females longer, but with the same intensity as well-fed females. Predation risk eliminated aggression toward males by well-fed females. In summary, males were able to identify the body condition of prospective mates from chemotactile cues alone, but when females were present, predation risk had little impact on the aspects of courtship and mating that we documented.
The intraspecific diversity of the few mygalomorph spiders in southern Appalachia has received considerable attention, revealing highly localized and deeply divergent populations and in some cases cryptic species. The araneomorph fauna of the region has received comparatively little study, due to its higher diversity, more tentative taxonomy, and perhaps perception that short-range endemicity might be lower. In this study, we examined this last assumption, surveying patterns of intraspecific diversity across Araneomorphae occurring in the leaf litter of high elevation spruce-fir sky islands of southern Appalachia, as revealed by population level metabarcoding. In most species, intraspecific haplotypic diversity, while high, revealed little geographic pattern, generally supporting assumptions of low regional endemicity. Of 50 spider species found in spruce-fir forest litter, more than 30 occur more widely, and showed little sign of subdivision even over major biogeographic features in the region, such as the French Broad River valley. By analyzing 10 of these well-sampled species with population genetic and phylogeographic methods, we found that only a few showed significant population level subdivisions. We suggest that the ballooning behavior of most immature araneomorph spiders is sufficiently frequent to overcome divergence of otherwise isolated populations, and that in those few exceptions the species are more specialized to particular microhabitats in the spruce-fir forest and such unpredictable dispersal may have been selected against.
Orb web weaving spiders, like Argiope trifasciata (Forsska & ring;l, 1775), rely on sticky aggregate glue droplets on the capture spiral of their web to retain prey. Here, we compared the protein composition of the glue droplets placed at the bottom of the web early in capture spiral construction, to those placed at the inside of the web late in web construction. We found a lower abundance of aggregate proteins in the inner web, where the droplets are smaller, are less extensible, and contain a higher proportion of water. Interestingly, we also found that pyriform spidroin, which anchors bridging lines of the web to the substrate, was more abundant in the inner region of the web, which has a higher density of capture spiral-radial line junctions. We propose that pyriform spidroin has a previously unidentified role in orb webs: anchoring the capture spiral to radial lines.
A new troglobitic species belonging to the genus Paratricommatus Piza, 1943 (Cryptogeobiidae), was found in a cave in the Pains municipality, Minas Gerais state, Brazil, and is described here. Paratricommatus infernalis sp. nov. is distinguished from all other species in the genus by having the IV femur 1.5-2.5 longer than the dorsal shield (instead of the IV femur shorter than the dorsal shield) and small eyes with reduced pigmentation. This new species presents several troglomorphic traits, such as elongated legs and different degrees of reduction in integumentary and ocular pigmentation, in addition to being absent in epigean environments. Thus, it is considered a troglobitic species and may represent a relic, as evidenced by its geographic isolation from other Cryptogeobiidae species.
Systemic optimization of RNA extraction protocols in non-model arachnids is indispensable for gene expression studies, including transcriptome sequencing and analyses. Spinnerets of the Neotropical tarantula Grammostola actaeon (Pocock, 1903) (family Theraphosidae) were used to evaluate the performance of two RNA extraction reagents and three commercially available kits for isolating total RNA from small eukaryotic tissue samples. Total RNA was extracted from spinneret tissues, using two samples for each method. We used the commercially available reagents TRIzol and NucleoZOL and the RNA extraction kits NucleoSpin and NucleoSpin XS (Macherey Nagel) and Total RNA Purification Kit (Norgen Biotek Corp). Quantification using Qubit revealed that NucleoSpin, Norgen, and NucleoSpin XS resulted in the highest RNA yields respectively, while Nanodrop analysis ranked Norgen, TRIzol, NucleoSpin, NucleoSpin XS in descending order. Bioanalyzer analysis indicated that Nucleospin, and NucleoSpin XS delivered the best results for our samples. While each method successfully yielded sufficient RNA for RNA-seq experiments, variations in RNA quality among methods indicate differences in their suitability for specific applications. Our data provide further evidence that RNA integrity number (RIN)-based assessments in G. actaeon may not be reliable for evaluating RNA quality due to a widespread occurrence of the 'gap deletion' phenomenon in arthropods. RNA from species with 28S rRNA collapsed can yield high-quality transcriptomes, suggesting that current RIN-based assessments may not be reliable for evaluating RNA quality in many non-model invertebrates. Overall, differences in results of commercially available RNA extraction reagents/kits should be considered when selecting the most appropriate RNA extraction method for gene expression analysis.
Among the variety of wolf spiders in Europe, there are some uncommon and poorly known species. An example is Pardosa paludicola (Clerck, 1757), which is classified as endangered and rare in some countries. We used a capture-mark-recapture method to examine the biology of mature P. paludicola individuals, focusing on the movement ranges of this spider. We marked 714 individuals and more than 10% of them were recaptured (# 4.5% and 2 14.7%). The median movement range was calculated at 5-6 m for both sexes and the maximum distances reached 58-69 m in 3-4 days. In the context of conservation efforts for this species, it seems important to provide large open areas of high humidity, with low human interference.
We developed a monoclonal antibody (MAb) to Platynota stultana (Tortricidae, common name omnivorous leafroller), a key pest of grape in California, and used it to detect predation by spiders in San Joaquin Valley vineyards. Using an enzyme-lined immunosorbant assay, we found a MAb with high specificity to P. stultana, with no cross reaction to several non-lepidopteran insects, and minor reaction to other lepidopteran species. We tested the MAb on four spiders: Cheiracanthium dae) and Hololena nedra Chamberlin & Ivie, 1942 (Agelenidae), and found for all but C. inclusum, there was reactivity to spiders which had eaten P. stultana larvae in the laboratory. We sampled spiders from two Fresno County vineyards, assaying by species and weight at antigen dilutions of 1:100 and 1:1000. None of the small-sized Oxyopes spp. or H. nedra specimens was positive, but 8.8% of the medium-sized Oxyopes spp. and 33.3% of the medium- and large-sized H. nedra specimens were. 28.5% of the small-, 57.1% of the medium- and 66.6% of the large-sized T. pacificus specimens tested positive. Our interpretation is that the H. nedra positives resulted from P. stultana moth capture, and that Oxyopes spp. prey upon P. stultana larvae, but have a limited ability to capture them. Trachelas pacificus appears to be an effective predator of immature P. stultana, capable of finding and consuming those hidden in their nests, and may play a positive role in lowering its population density.
In this study, we provide an update on the knowledge of vertebrate-eating jumping spiders. Twenty-four reports of jumping spider predation on vertebrates are known, which are attributed to seven species: Hyllus diardi (Walckenaer, 1837), FO Pickard-Cambridge, 1901, P. regius CL Koch, 1846, and an unknown species apparently related to Hasarius Simon, 1871. In addition, several unsuccessful predation attempts by Phidippus audax (Hentz, 1845) on hummingbird and chickadee nestlings are documented. Furthermore, an incident of Phidippus otiosus (Hentz, 1846) feeding on an oversized gecko carcass (likely a case of scavenging) is reported. Overall, incidents of vertebrate predation by salticids are likely to be, in most cases, very rare chance encounters between a tiny vertebrate and a hungry spider. In contrast, the case of Phidippus regius is unique for salticids as-to the current state of knowledge-this is the only salticid species in which vertebrate consumption has been reported numerous times (n = 18) and in many different locations (11 different Florida counties, USA).
During a study of the pseudoscorpion fauna of caves in northeastern Brazil, a new species of the genus Neoallochernes Hoff, 1947 was discovered. Morphological analysis suggests that the new species, named Neoallochernes catimbauensis sp. nov., is closely related to N. cubanus Muchmore, 1992. Neoallochernes catimbauensis can be distinguished from other congeners by its spermathecae morphology, trichobothria ib and ist positioned subbasally, trichobothrium isb located subdistally to the middle of the finger and proximal to est. Femur length/width ratios were 2.83x (s?) and 2.42-2.62x (a); patella width ratios were 2.34x (s?) and 2.29-2.31x (a); and chela (without pedicel) ratios were 3.34x (s?) and 3.18-3.21x (a). In addition, ecological observations, distribution maps including past and present records, and a taxonomic identification key are provided.
Sticky spiral construction behavior in orb-weaving spiders is strikingly flexible: 10 to 16 different cues influence the hundreds of decisions that a spider makes while building the sticky spiral in an orb. Several variables that are influenced by radial tensions, including the frequencies and amplitudes of vibrations and the extensibility and tensions of the radii, have been repeatedly mentioned as possible cues guiding sticky spiral placement. Nevertheless, previous studies have suggested that radius tensions do not affect sticky spiral spacing. These tests were complicated, however, by the tight correlations between variables due to the highly regular geometry of orbs, possible context-dependent variation in the use of cues, and the intrinsic difficulty of demonstrating the absence of an effect. Greater certainty regarding tension-dependent cues is crucial for understanding the cues guiding orb construction, so this study extends these experiments, examining the effects of both increasing and decreasing radius tension, and of different sequences and magnitudes of changes. The results confirm previous findings: changes in radius tensions did not influence sticky spiral spacing decisions in consistent ways and generally failed to produce statistically significant effects. I argue that the likely reason why spiders do not use tension-dependent variables to guide sticky spiral placement is that such cues are unreliable because the spider's own weight substantially alters the tensions on nearby web lines in complex and variable ways.
Harvestmen are generally considered to be omnivores. In contrast to most other arachnids that are fluid feeders, harvestmen are capable of ingesting solid food particles and may consume invertebrates, small vertebrates, plant tissues, fungi, and detritus. However, for most species, quantitative diet data are lacking. Stable nitrogen isotope analysis provides a means to measure the contribution of these materials to the diet over the time scale of tissue turnover, and thus quantify trophic position. Examination of fecal material can provide additional evidence of recent feeding, which can further complement field observations and isotopic analyses. We investigated the diet of Erginulus clavotibialis (F.O. Pickard-Cambridge, 1905) (Arachnida, Opiliones, Cosmetidae) in western Belize, using stable isotope analysis and scanning electron microscopy of fecal samples. We also examined nitrogen isotopic ratios for carnivores (scorpions and spiders), herbivores (grasshoppers and katydids), and preliminary measures for two other harvestmen species, ants, and termites. Erginulus clavotibialis had delta 15N signatures similar to scorpions and spiders, indicating carnivory. Nymphs and adults (females and males) of E. clavotibialis did not differ significantly in their trophic level despite possessing chelicerae and pedipalps that differ substantially in relative size and morphology. Fecal samples contained considerable evidence of arthropod consumption, as fragments of legs and exoskeleton were evident. Our study provides an initial quantification of harvestman diet and documents that E. clavotibialis is primarily carnivorous.
Mexico boasts the highest number of known ricinuleid species worldwide, however the diversity from North America is still poorly known. Herein, we evaluate Pseudocellus pelaezi (Coronado-Gutierrez, 1970), a dimorphic species distributed in San Luis Potos & imath; and Tamaulipas, northeastern Mexico. This species represents the first known dimorphic species of ricinuleids, welldocumented based on morphology, ultrastructure, and genetic distance. The average intraspecific genetic distance (p-distance) at the mitochondrial cytochrome c oxidase subunit 1 (CO1) within P. pelaezi was 4.1%, whereas a much higher value of 14.6% was found between analyzed species of Pseudocellus Platnick, 1980. Although the genetic distance within the species is >4%, the morphology of primary sexual structures such as the male copulatory apparatus of leg III and the female spermathecae were strongly conserved across all the specimens. However, the morphology of a secondary sexual structure, male femora II, showed variation, with some males possessing a thin femora II (morpho 1-M1) (homeomorphic) and others with a wide femora II (morpho 2-M2) (heteromorphic). This male dimorphism, even within the same population of P. pelaezi, might be considered as a direct effect of sexual competition among males to mate with females, however more studies are needed to test this in ricinuleids. This could be done by studying and evaluating the sexual behavior in combination with the genetic evidence from specimens across several populations, offering insight into whether such dimorphism and/or genetic variation is correlated with sexual competition or represents underestimated diversity yet to be described.
Aversive conditioning is a form of associative learning. Here, we investigated learning and memory capacity of the harvester Mischonyx squalidus (Roewer, 1913), to examine the formation of short (STM) and long-term memories (LTM). First, we trained harvesters to associate an aversive stimulus (shock) with a neutral stimulus (tea odor). Each subject went through three consecutive trials, in which pairings between the stimuli lasted for 3s, with intervals of 1 (STM) and 30 (LTM) min. Subsequently, to test memory, we introduced the subjects in a choice arena where they could choose between staying in either of two areas: impregnated with tea chemicals or blank. We did this immediately after the conditioning phase or 24h after it. Both protocols were successful for STM within the same-day test, but not for LTM on the following day. Insummary, we provide a new method to train aversive conditioning in harvesters and evidence for short-term memory.
Net-casting spiders (Deinopidae) are cribellate spiders that spin a rectangular, sticky net that is held stretched between the claws of their first two pairs of legs. Deinopids produce eight distinct silk types, but knowledge of the silk-producing morphologies is mostly limited to the spigots associated with different fibers. As there have been no studies of deinopid silk gland structure, we dissected all the silk glands from Deinopis spinosa Marx, 1889 and document their number and morphology. We found silk gland position and morphology consistent with the type and number of silk spigots described for Deinopidae. Notably, for the first time, we describe the silk glands associated with cribellate silk: paracribellate, pseudoflagelliform, and cribellar silk glands. Our findings support the homology of pseudoflagelliform glands with araneoid flagelliform glands and will have importance for informing our understanding of spider web evolution.
The reproductive phenology of Himalphalangium spinulatum (Roewer, 1911) (Eupnoi: Phalangiidae), which overwinter as juveniles and mature in early summer, was surveyed at a riparian forest on the Sendai River, Tottori City, Honshu, Japan. Females became adults about 3-4 days earlier than males. The body weight of females and males and the number of mature eggs retained in females were highest at the age about a week after the final molting, suggesting a shorter time is needed to commence mating and oviposition in this species. This might be the reason for the shorter time lag in maturation between females and males in this species compared to other species of protogynous harvestmen.
