Arachnid Order Research Articles

Sequence capture phylogenomics of historical ethanol-preserved museum specimens: Unlocking the rest of the vault.

Natural history collections play a crucial role in biodiversity research, and museum specimens are increasingly being incorporated into modern genetics-based studies. Sequence capture methods have proven incredibly useful for phylogenomics, providing the additional ability to sequence historical museum specimens with highly degraded DNA, which until recently have been deemed less valuable for genetic work. The successful sequencing of ultraconserved elements (UCEs) from historical museum specimens has been demonstrated on multiple tissue types including dried bird skins, formalin-fixed squamates and pinned insects. However, no study has thoroughly demonstrated this approach for historical ethanol-preserved museum specimens. Alongside sequencing of "fresh" specimens preserved in >95% ethanol and stored at -80°C, we used extraction techniques specifically designed for degraded DNA coupled with sequence capture protocols to sequence UCEs from historical museum specimens preserved in 70%-80% ethanol and stored at room temperature, the standard for such ethanol-preserved museum collections. Across 35 fresh and 15 historical museum samples of the arachnid order Opiliones, an average of 345 UCE loci were included in phylogenomic matrices, with museum samples ranging from six to 495 loci. We successfully demonstrate the inclusion of historical ethanol-preserved museum specimens in modern sequence capture phylogenomic studies, show a high frequency of variant bases at the species and population levels, and from off-target reads successfully recover multiple loci traditionally sequenced in multilocus studies including mitochondrial loci and nuclear rRNA loci. The methods detailed in this study will allow researchers to potentially acquire genetic data from millions of ethanol-preserved museum specimens held in collections worldwide.

The oldest short-tailed whipscorpion (Schizomida): A new genus and species from the Upper Cretaceous amber of northern Myanmar

Arachnids are an ancient lineage of arthropods and orders such as scorpions, harvestmen and mites have their fossil origins in the Silurian or Devonian. Another order with potentially old origins is the short-tailed whipscorpions, or schizomids (Arachnida: Schizomida). These animals have a fragmentary fossil record with species either described or documented from Dominican amber (Miocene: Chattian), drill core sediments from the Oligocene in China, and the upper Pliocene (Zanclean) of Arizona. Here, we describe the first named example of a short-tailed whipscorpion from Upper Cretaceous amber (Myanmar: Hukawng Valley) based on male morphological features. Mesozomus groehni gen. et sp. n. cannot be assigned to any Recent genera of schizomids and preserves a unique mix of plesiomorphic (e.g. the retention of eyes) and apomorphic characters (e.g. enlarged femur IV) that merit future evaluation within a phylogenetic context. We extend the fossil record of schizomids by ca. 65 million years, from the Paleogene to the Mesozoic, and add the twelfth order of arachnids to the diverse arachnid biota documented from Burmese amber.

Stenochrus portoricensis (Arachnida: Schizomida) living in a nest of the fire ant Solenopsis saevissima (Hymenoptera: Formicidae) in the Atlantic Forest, Brazil

Schizomida is an arachnid order widely distributed in tropical and subtropical regions, commonly found in humid and warm environments such as leaf litter, on the underside of rocks, and in caves. Stenochrus portoricensis has been observed in association with termite and ant nests. In this study, we report for the first time S. portoricensis living within a nest of the fire ant Solenopsis saevissima. This new interaction triggers interest in the mechanisms used by the schizomid to deceive and be undetected by fire ants, as well as the potential advantages for the schizomid in living within Solenopsis nests.

Deformed Wing Virus in Honeybees and Other Insects.

Deformed wing virus (DWV) has become the most well-known, widespread, and intensively studied insect pathogen in the world. Although DWV was previously present in honeybee populations, the arrival and global spread of a new vector, the ectoparasitic mite Varroa destructor, has dramatically altered DWV epidemiology. DWV is now the most prevalent virus in honeybees, with a minimum average of 55% of colonies/apiaries infected across 32 countries. Additionally, DWV has been detected in 65 arthropod species spanning eight insect orders and three orders of Arachnida. Here, we describe the significant progress that has been made in elucidating the capsid structure of the virus, understanding its ever-expanding host range, and tracking the constantly evolving DWV genome and formation of recombinants. The construction of molecular clones, working with DWV in cell lines, and the development of immunohistochemistry methods will all help the community to move forward. Identifying the tissues in which DWV variants are replicating and understanding the impact of DWV in non-honeybee hosts are major new goals.

Increasing species sampling in chelicerate genomic-scale datasets provides support for monophyly of Acari and Arachnida

Chelicerates are a diverse group of arthropods, represented by such forms as predatory spiders and scorpions, parasitic ticks, humic detritivores, and marine sea spiders (pycnogonids) and horseshoe crabs. Conflicting phylogenetic relationships have been proposed for chelicerates based on both morphological and molecular data, the latter usually not recovering arachnids as a clade and instead finding horseshoe crabs nested inside terrestrial Arachnida. Here, using genomic-scale datasets and analyses optimised for countering systematic error, we find strong support for monophyletic Acari (ticks and mites), which when considered as a single group represent the most biodiverse chelicerate lineage. In addition, our analysis recovers marine forms (sea spiders and horseshoe crabs) as the successive sister groups of a monophyletic lineage of terrestrial arachnids, suggesting a single colonisation of land within Chelicerata and the absence of wholly secondarily marine arachnid orders.

Distribution of cave-dwelling pseudoscorpions (Arachnida) in Brazil

Pseudoscorpions are among the most diverse of the smaller arachnid orders, but there is relatively little information about the distribution of these tiny animals, especially in Neotropical caves. Here, we map the distribution of the pseudoscorpions in Brazilian caves and record 12 families and 22 genera based on collections analyzed over several years, totaling 239 caves from 13 states in Brazil. Among them, two families (Atemnidae and Geogarypidae) with three genera (Brazilatemnus Muchmore, 1975, ParatemnoidesHarvey, 1991 and Geogarypus Chamberlin, 1930) are recorded for the first time in cave habitats as, well as seven other genera previously unknown for Brazilian caves (Olpiolum Beier, 1931, Pachyolpium Beier 1931, TyrannochthoniusChamberlin, 1929, Lagynochthonius Beier, 1951, Neocheiridium Beier 1932, Ideoblothrus Balzan, 1892 and Heterolophus Tömösváry, 1884). These genera are from families already recorded in this habitat, which have their distributional ranges expanded for all other previously recorded genera. Additionally, we summarize records of Pseudoscorpiones based on previously published literature and our data for 314 caves. We present these data in maps, considering the Brazilian biogeographical provinces. For the genus SpelaeochernesMahnert, 2001, we reevaluate its Schiner-Racovitza status and propose that all species represent troglobites. Finally, we discuss the ranges of the pseudoscorpion families/genera.

The family Bombyliidae in the Kingdom of Saudi Arabia (Diptera: Brachycera: Asiloidea).

Bombyliidae, also known as "Bee flies", is one of the dipteran families that have species of potential use as biological control agents, as their larvae are predators or parasitoids of eggs, larvae, prepupae or pupae of other insects. The hosts of Bombyliidae are found within six orders of insects: Lepidoptera, Orthoptera, Hymenoptera, Diptera, Coleoptera, and Neuroptera, in addition to the arachnid order Araneae (Spiders). However, almost half of all host records are from bees and wasps (Hymenoptera). The present work provides a catalogue of bee flies (Family Bombyliidae) in the Kingdom of Saudi Arabia. Old World synonymies, type localities, world distributions by biogeographic realm(s) and country, Saudi Arabian localities and dates of collection are provided. A total of 116 species belonging to 40 genera, 12 tribes and 10 subfamilies has been catalogued. Hosts and/or habitat data, where known, are given under the proper genera and/or species. Colored photographs of some species are provided.

Morphological and cytogenetic characteristics of Neobisium (Blothrus) slovacum Gulička, 1977 (Pseudoscorpiones, Neobisiidae), the northernmost troglobitic species of the subgenus Blothrus in Europe

A redescription is provided of the adult, tritonymph and deutonymph life stages of the troglobitic Neobisium (Blothrus) slovacum Gulička, 1977, which is known from Slovakia and Hungary. Material examined included 35 previously deposited museum specimens and 15 newly collected specimens. In addition, the karyotype and distribution of 18S rDNA clusters are described, using fluorescence in situ hybridization (FISH). The male karyotype of N.slovacum comprises 69 chromosomes, with a predominance of biarmed chromosomes, and an X0 sex chromosome system. Two pairs of signals for 18S rDNA on biarmed chromosomes (submetacentric and metacentric) of different sizes were identified. The present study provides the first information about the distribution of these clusters in the arachnid order Pseudoscorpiones. The geographic distribution of the species is summarized and mapped. Neobisiumslovacum is endemic to the Slovak and Aggtelek Karst area in southern Slovakia and north-western Hungary, where it has been recorded from 16 caves. One of these, Hačavská cave (in Slovakia), is the northernmost locality known for any species of the subgenus Blothrus.

Seasonal diet of Asellia tridens (Chiroptera: Hipposideridae) in North-Western Africa

The seasonal variations of the diet of the desert Trident leaf-nosed bat, Asellia tridens, were investigated using dropping analyses during the whole year 2015 in the Timimoun region, south-western Algerian Sahara. We identified one order of arachnids (Araneae) and ten orders of insects: Coleoptera, Hymenoptera, Diptera, Orthoptera, Mantodea, Hemiptera, Isoptera, Ephemeroptera, Blattodea and Odonata in a decreasing rank. Coleoptera (31.07%) were Carabidae, Curculionidae, Chrysomelidae, Tenebrionidae, Aphodidae, Scarabaeidae, and Histeridae. Hymenoptera (21.31%) were Formicidae, Myrmicidae and Vespidae, Diptera (13.78%) were Culicidae and Tabanidae, and Orthoptera (11.40%) were Acrididae and Gryllidae. The autumn-winter diet (October to December) included a large amount of Odonata, Scarabaeidae, Blattodea, Acrididae and Myrmicidae. The spring-summer diet (February to August) was characterized mainly by Chrysomelidae, Vespidae, Tenebrionidae, Aphodidae and Araneae. As other desert bat species A. tridens displays a combination of opportunism and selective predation depending on the abundance of insect groups.

Sexual dimorphism in the Arachnid orders.

Sexual differences in size and shape are common across the animal kingdom. The study of sexual dimorphism (SD) can provide insight into the sexual- and natural-selection pressures experienced by males and females in different species. Arachnids are diverse, comprising over 100,000 species, and exhibit some of the more extreme forms of SD in the animal kingdom, with the males and females of some species differing dramatically in body shape and/or size. Despite this, research on arachnid SD has primarily focused on specific clades as opposed to observing traits across arachnid orders, the smallest of which have received comparatively little attention. This review provides an overview of the research to date on the trends and potential evolutionary drivers for SD and sexual size dimorphism (SSD) in individual arachnid orders, and across arachnids as a whole. The most common trends across Arachnida are female-biased SSD in total body size, male-biased SSD in relative leg length and SD in pedipalp length and shape. However, the evolution of sexually dimorphic traits within the group is difficult to elucidate due to uncertainty in arachnid phylogenetic relationships. Based on the dataset we have gathered here, we highlight gaps in our current understanding and suggest areas for future research.

Distribution of cave-dwelling pseudoscorpions (Arachnida) in Brazil

Pseudoscorpions are one of the most diverse of the smaller arachnid orders but there is relatively little information about the distribution of these tiny animals, especially in Neotropical caves. Here we map the distribution of the Pseudoscorpiones in Brazilian caves with record of 12 families and 22 genera, total 313 caves from 13 states. Among them, two families (Atemnidae and Geogarypidae) with three genera (Brazilatemnus Muchmore, 1975, Paratemnoides Harvey, 1991 and Geogarypus Chamberlin, 1930) are recorded for the first time in cave habitat as well as other seven genera previously unknown for Brazilian caves (Olpiolum Beier, 1931, Pachyolpium Beier 1931, Tyrannochthonius Chamberlin, 1929, Lagynochthonius Beier, 1951, Neocheiridium Beier 1932, Ideoblothrus Balzan, 1892 and Heterolophus Tömösváry, 1884) but these genera are from families already recorded in this habitat, and have their distributional ranges expanded for all other previously recorded genera. We present these data in maps, considering the biogeographical provinces. For the genus Spelaeochernes Mahnert, 2001, we re-evaluate its Schiner-Racovitza status and propose the troglobite status. Finally, we discuss the ranges of the pseudoscorpion families/genera for Brazilian caves (Suppl. material 1).

Transcriptomic Analysis of Pseudoscorpion Venom Reveals a Unique Cocktail Dominated by Enzymes and Protease Inhibitors.

Transcriptomic and genomic analyses have illuminated the diversity of venoms in three of the four venomous arachnid orders (scorpions, spiders, and ticks). To date, no venom gland transcriptome analysis has been available for pseudoscorpions, the fourth venomous arachnid lineage. To redress this gap, we sequenced an mRNA library generated from the venom glands of the species Synsphyronus apimelus (Garypidae). High-throughput sequencing by the Illumina protocol, followed by de novo assembly, resulted in a total of 238,331 transcripts. From those, we annotated 131 transcripts, which code for putative peptides/proteins with similar sequences to previously reported venom components available from different arachnid species in protein databases. Transcripts putatively coding for enzymes showed the richest diversity, followed by other venom components such as peptidase inhibitors, cysteine-rich peptides, and thyroglobulin 1-like peptides. Only 11 transcripts were found that code for putatively low molecular mass spider toxins. This study constitutes the first report of the diversity of components within pseudoscorpion venom.

Morphogeometric variation in Phrynus barbadensis (Pocock, 1893) (Amblypyghi: Phrynidae) from Colombia

Amblypygi is a small order of arachnids with features similar to spiders. In Colombia, this order has been subject to low attention, the main investigations are focused towards a taxonomic level. Recently, the geometric morphometrics has proven to be an useful tool for determining shape differences in scorpions and spiders. Due to this, we used geometric morphometrics to determine intraspecific variation in three Colombian populations of Phrynus barbadensis . We digitalized 16 anatomical points over the carapace and 15 in patella by combining landmarks and sliding semilandmarks; the coordinates were aligned by generalized Procrustes analysis. Canonical Variates Analysis was implemented with proportions of re-classified groups and MANOVA. We found significant differences of carapace conformation between populations; all specimens were 80% correctly classified. Statistical analyses of variance (ANOVA) found significant differences in carapace and patella isometric size among populations; the main carapace differences occur in anterior, posterior and right margins. The observed variation could be associated with the environmental differences between localities

Arachnids in Bitterfeld amber: A unique fauna of fossils from the heart of Europe or simply old friends?

Bitterfeld amber, sometimes referred to as Saxon or Saxonian amber, is a potentially significant but poorly known source of arthropod data for the Palaeogene of northern Europe. An important aspect is a long-standing controversy about the age of this amber: namely whether it is equivalent to, and perhaps merely a southerly extension of, the better-known Baltic amber, or whether it is a unique and geological younger deposit sampling a different fauna. Here, we briefly review the Bitterfeld arachnids with particular emphasis on how these data could be used to elucidate the age of this deposit. Five arachnid orders have been recorded from Bitterfeld amber: spiders (Araneae), acariform mites (Acariformes), parasitiform mites (Parasitiformes), harvestmen (Opiliones) and pseudoscorpions (Pseudoscorpiones). This is a lower diversity than Baltic amber, where scorpions (Scorpiones) and camel spiders (Solifugae) have also been recorded. Spiders are the most comprehensively studied group, with more than 75 described species. Other groups such as pseudoscorpions and mites appear to be very diverse, but are virtually undescribed. Morphological overlap is apparent in the arachnid fauna and 40 species are currently shared between Baltic and Bitterfeld amber whilst 50 species are unique to the Bitterfeld deposit. At the family level overlap is even higher, but in all groups Baltic amber appears more diverse than Bitterfeld. This overlap may be interpreted as evidence for temporal conspecifity of the Baltic and Bitterfeld ambers, albeit with the Bitterfeld and Baltic ambers possibly representing independent localities within a larger Eocene European amber area which also included the Rovno amber from the Ukraine. However, caution should be exercised because the taxonomic foundation for such assumptions is far from comprehensive, most of the material remains to be studied in detail using modern techniques of morphological reconstruction. There are further issues with date estimates because some arachnid groups show extraordinary morphological stasis over time, even at species level, which may bias the analyses available. Here, we review the available knowledge on Bitterfeld arachnids and discuss how a detailed assessment of this fauna, and other arthropod taxa, could be generated. Several natural history museums – including Hamburg and Berlin – as well as private collectors host major assemblages of Bitterfeld fossils which may help to clarify the debate about the age and provenance of the material, and the extent to which (morpho)-species were maintained both over geographical distances and potentially geological time.

Origin of spiders and their spinning organs illuminated by mid-Cretaceous amber fossils.

Understanding the genealogical relationships among the arachnid orders is an onerous task, but fossils have aided in anchoring some branches of the arachnid tree of life. The discovery of Palaeozoic fossils with characters found in both extant spiders and other arachnids provided evidence for a series of extinctions of what was thought to be a grade, Uraraneida, that led to modern spiders. Here, we report two extraordinarily well-preserved Mesozoic members of Uraraneida with a segmented abdomen, multi-articulate spinnerets with well-defined spigots, modified male palps, spider-like chelicerae and a uropygid-like telson. The new fossils, belonging to the species Chimerarachne yingi, were analysed phylogenetically in a large data matrix of extant and extinct arachnids under a diverse regime of analytical conditions, most of which resulted in placing Uraraneida as the sister clade of Araneae (spiders). The phylogenetic placement of this arachnid fossil extends the presence of spinnerets and modified palps more basally in the arachnid tree than was previously thought. Ecologically, the new fossil extends the record of Uraraneida 170 million years towards the present, thus showing that uraraneids and spiders co-existed for a large fraction of their evolutionary history.

Current views on chelicerate phylogeny—A tribute to Peter Weygoldt

Peter Weygoldt pioneered studies of arachnid phylogeny by providing the first synapomorphy scheme to underpin inter-ordinal relationships. Since this seminal work, arachnid relationships have been evaluated using morphological characters of extant and fossil taxa as well as multiple generations of molecular sequence data. While nearly all datasets agree on the monophyly of Tetrapulmonata, and modern analyses of molecules and novel morphological and genomic data support Arachnopulmonata (a sister group relationship of Scorpiones to Tetrapulmonata), the relationships of the apulmonate arachnid orders remain largely unresolved. Three threads may allow us to resolve the recalcitrant phylogeny of arachnids: the careful evaluation of large amounts of molecular data; novel techniques grounded in comparative morphology and evolutionary developmental biology, which add improved homology statements and explain the transition between character states; and new fossil discoveries, which continue to incorporate relevant novel data to the discussion of the relationships among the arachnid orders.

Giovanni Canestrini's heritage at the Zoology Museum of Padova University (Italy): a rediscovery of his arachnological collections and described species

Giovanni Canestrini (1835–1900) was the pioneer of arachnology in Italy, who published the first catalogue of Italian spiders and a total of 87 papers in the field. His interests covered almost all the Italian arachnid orders, although in the last part of his life he focused on acarology, in which he became a leading world expert. The remains of Canestrini's arachnological collection deposited in the Zoology Museum of Padova University are represented by spiders (about 850 tubes), mites (438 microscope slides, 115 tubes), harvestmen (120), pseudoscorpions (63), scorpions (19) and solifuges (1). The collection is now part of a large revision project aiming at better understanding and clarifying the scientific heritage of Canestrini, including an inventory of the type material from Canestrini and other European arachnologists who contributed to his collection (e.g., T. Thorell). The first results of the collection revision outlining different arachnid orders and highlighting the occurrence of type material are presented here. Brief historical information on Canestrini and his pupils is also provided.

Optimizing survey methods for spiders and harvestmen assemblages in an Amazonian upland forest

Invertebrates can be sampled using any of several well-established, rapid and cost-effective methods for documenting species richness and composition. Despite their many differences, different orders of arachnids have been often sampled together in various studies. Active nocturnal search has been long considered the most efficient method for sampling spiders and harvestmen in tropical forests. We compared the number of species and composition of spiders and harvestmen simultaneously sampled using three sampling methods beating tray, active nocturnal search and Winkler traps at areas along the Urucu River, Coari, Amazonas. We found that a reasonable inventorying of harvestmen can be accomplished solely by nocturnal search, whereas the beating tray and Winkler approaches are redundant. For spiders, both the nocturnal and beating tray methods were complementary and are needed to provide a more complete picture of spider assemblages. An inventory based solely on nocturnal search saves 75% of the survey costs for harvestmen assemblages and 46% for spider assemblages. Based on our findings we propose that different taxonomic groups (e.g. harvestmen and spiders) should be sampled separately in tropical forests, especially for monitoring purposes, and different sets of methods should be combined for each according to their most efficient and best cost-benefit performance.

A review of Burmese amber arachnids

Fossils from the mid-Cretaceous (c. 99 Ma) Myanmar (Burma) amber include all extant orders of Arachnida, including the earliest representatives of Schizomida, Parasitiformes, and Palpigradi. Schizomids are figured from Burmese amber herein for the first time. The most abundant and diverse arachnid order is the Araneae, with 38 families, 93 genera, and 165 species recorded to date. The araneofauna is dominated by haplogynes and palpimanoids, whilst araneoids are rare and members of the RTA clade absent. The arachnofauna is typical of a tropical rainforest habitat, which concurs with evidence from other Burmese amber biota.

First global molecular phylogeny and biogeographical analysis of two arachnid orders (Schizomida and Uropygi) supports a tropical Pangean origin and mid‐Cretaceous diversification

AbstractAimWe sought to illuminate the history of the arachnid orders Schizomida and Uropygi, neither of which have previously been subjected to global molecular phylogenetic and biogeographical analyses.LocationSpecimens used in this study were collected in all major tropical and subtropical areas where they are presently found, including the Americas, Africa, Australia and the Indo‐Pacific region.MethodsFrom field‐collected specimens, we sequenced two nuclear and two mitochondrial markers, combined these with publicly available data, and conducted multi‐gene phylogenetic analyses on 240 Schizomida, 24 Uropygi and 12 other arachnid outgroups. Schizomid specimens included one specimen from the small family Protoschizomidae; other schizomid specimens were in Hubbardiidae, subfamily Hubbardiinae, which holds 289 of the order's 305 named species. We inferred ancestral areas using the Dispersal‐Extinction‐Cladogenesis model of range evolution, and we used fossil calibrations to estimate divergence times.ResultsWe recovered monophyletic Schizomida and Uropygi as each other's sister group, forming the clade Thelyphonida, and terminals from the New World were usually positioned as the earliest diverging lineages. The ancestral area for schizomids reconstructed unambiguously to the region comprised of Mexico, Southern California and Florida (the xeric New World subtropics). Optimal trees suggested a single colonization of the Indo‐Pacific in both orders, although this did not receive bootstrap support. Molecular dating gave an Upper Carboniferous origin for each order, and a mid‐Cretaceous expansion of Schizomida, including the origin and initial diversification of those in the Indo‐Pacific.Main conclusionsAncestral area reconstructions, molecular dating and fossil evidence all support an Upper Carboniferous, tropical Pangean origin for Thelyphonida, Schizomida and perhaps Uropygi. Much of this region became unsuitable habitat for these arachnids during the breakup of Pangea, but they persisted in the area that is now Meso‐ and South America. From there they then expanded to the Indo‐Pacific, where schizomids today display an idiosyncratic combination of microendemism and long‐range dispersal.