Walking Legs Research Articles

Optimal synthesis of planar eight-link walking leg mechanism using genetic algorithm

Optimal synthesis of planar eight-link walking leg mechanism using genetic algorithm

Click Chemistry-Actuated Digital DNA Walker Confined on a Single Particle toward Absolute MicroRNA Quantification.

A versatile single magnetic nanoparticle (MNP)-confined, click chemistry-actuated digital DNA walker (ddWalker) machine is devised for the absolute quantification of microRNA (miRNA). This delicate ddWalker allows one target molecule to fix one DNA walking leg on a single MNP, following the Poisson statistics through a specific click chemical DNA ligation, which will initiate single molecule DNA walking to stepwise cleave the molecular beacon tracks strictly constrained on the leg-hold MNP without cross-particle reaction, fluorescently "lighting up" the exact MNP. Accordingly, the initial miRNA input can be digitally and faithfully reflected by the number of fluorescent-positive MNPs counted by a total internal reflection fluorescent microscope, enabling the absolute and precise miRNA quantification down to the femtomolar level without external calibration. This flexible ddWalker design provides a new digital signaling concept and elegantly expands the toolbox for digital biosensing.

Anatomical changes in postembryonic development of Pycnogonum litorale.

Sea spiders (Pycnogonida) are a small group of arthropods, sister to other chelicerates. They have an unusual adult bauplan, oligosegmented larvae, and a protracted postembryonic development. Pycnogonum litorale (Strøm, 1762) is an uncommonly long-lived sea spider with a distinctive protonymphon and adult anatomy. Although it was described ~250 years ago, little is known about its internal organization and development. We examined the anamorphic and early epimorphic development of this species using histology, light microscopy, and SEM, and provide the first comprehensive anatomical study of its many instars. Postembryonic development of P. litorale includes transformations typical of pycnogonids: reorganization of the larval organs (digestive, nervous, secretory), formation of the abdomen, trunk segments (+ appendages), primary body cavity and reproductive system. Specific traits include the accelerated articulation of the walking legs, formation of the subesophageal and posterior synganglia, and the system of twin midgut diverticula. In addition, P. litorale simultaneously lose the spinning apparatus and all larval appendages. We found that developmental changes occur in synchrony with changes in ecology and food sources. The transition from the anamorphic to the epimorphic period in particular is marked by considerable anatomical and lifestyle shifts. HIGHLIGHTS: Postembryonic development of P. litorale includes numerous anamorphic and epimorphic stages. The instars acquire abdomen, trunk segments, body cavity, and gonads, while losing all larval appendages. Developmental changes are synchronized with changes in lifestyle and food sources.

Structure of the pecten neuropil pathway and its innervation by bimodal peg afferents in two scorpion species.

The pectines of scorpions are comb-like structures, located ventrally behind the fourth walking legs and consisting of variable numbers of teeth, or pegs, which contain thousands of bimodal peg sensillae. The associated neuropils are situated ventrally in the synganglion, extending between the second and fourth walking leg neuromeres. While the general morphology is consistent among scorpions, taxon-specific differences in pecten and neuropil structure remain elusive but are crucial for a better understanding of chemosensory processing. We analysed two scorpion species (Mesobuthus eupeus and Heterometrus petersii) regarding their pecten neuropil anatomy and the respective peg afferent innervation with anterograde and lipophilic tracing experiments, combined with immunohistochemistry and confocal laser-scanning microscopy. The pecten neuropils consisted of three subcompartments: a posterior pecten neuropil, an anterior pecten neuropil and a hitherto unknown accessory pecten neuropil. These subregions exhibited taxon-specific variations with regard to compartmentalisation and structure. Most notable were structural differences in the anterior pecten neuropils that ranged from ovoid shape and strong fragmentation in Heterometrus petersii to elongated shape with little compartmentalisation in Mesobuthus eupeus. Labelling the afferents of distinct pegs revealed a topographic organisation of the bimodal projections along a medio-lateral axis. At the same time, all subregions along the posterior-anterior axis were innervated by a single peg’s afferents. The somatotopic projection pattern of bimodal sensillae appears to be common among arachnids, including scorpions. This includes the structure and organisation of the respective neuropils and the somatotopic projection patterns of chemosensory afferents. Nonetheless, the scorpion pecten pathway exhibits unique features, e.g. glomerular compartmentalisation superimposed on somatotopy, that are assumed to allow high resolution of substrate-borne chemical gradients.

A case of monofocal motor neuropathy with GM1 and GD1b antibodies improved with intravenous immunoglobulin

Multifocal motor neuropathy is a purely motor neuropathy with a probably dysimmune pathogenesis, supported by the presence of anti-GM1 IgM antibodies in about half of the cases. Single nerve involvement allows for diagnosis of possible multifocal motor neuropathy. We present the case of a middle age man presenting with progressive weakness and hypotrophy in the left leg and difficulty in walking, in which we have diagnosed a dysimmune mononeuropathy. Treatment with IVIg was performed with substantial improvement. Although only one nerve is involved, early diagnosis of dysimmune mononeuropathy is important to start IVIg treatment that is often decisive.

Optimal 5R parallel leg design for quadruped robot gait cycle

This paper presents the design of optimal dimensions for a two degrees of freedom parallel mechanism used in quadruped for walking application. Serial linkages or open link mechanisms have less stiffness and poor dynamic performance, thus parallel mechanisms were developed. Many researchers have used symmetrical parallel leg for quadruped walking but force requirements are different in forward and return stroke, thus unsymmetrical parallel leg may be optimal. Using genetic algorithm, optimum link length values are obtained and the corresponding peak torque is also found.

A Noise-Immune Kalman Filter and Modelling forPedestrian Traffic Loads

The definition of design load with walking crowd excitation on these slender structures is a significant problem to human-induced vibration. To capture the characteristics of walking crowd loads, this article researches both the ground reaction force and ground reaction moment for 36 healthy adults. Firstly, a oscillate system modeling walking leg is used to build a governing equation, which further transformed into the discrete state space. Then the Kalman method is applied to filter the noises for the measured ground reaction force, which can well remove the noises hiding in the measured signals. In addition, the Fourier series are used to model the ground reaction force and ground reaction moment, and the first six corresponding coefficients are obtained and analyzed. This work comprehensively explores the excitation force and moment from walking pedestrian feet. The result of this study provides the reference of load design for these slender structures such as footbridges, grandstands, or stations under crowd excitation.

Cholinesterase characterization and effects of the environmental contaminants chlorpyrifos and carbofuran on two species of marine crabs, Carcinus maenas and Pachygrapsus marmoratus.

Among the most frequent targets for toxic effects of modern pesticides, namely organophosphates and carbamates, one may find cholinesterases (ChEs). ChEs exist in a wide variety of animals and have been used actively to discriminate among the environmental effects of different pollutant groups, including the aforementioned pesticides. This study had three purposes, namely (i) identifying the ChE forms present in tissues (eyes and walking legs muscle) of two crab species, Carcinus maenas and Pachygrapsus marmoratus; to (ii) determine the in vitro toxicological effects, and (iii) compare the sensitivity of such enzymatic forms towards commonly used anti-ChE pesticides, namely the organophosphate chlorpyrifos and the carbamate carbofuran. Our results showed that there was not a clear preference for any of the tested substrates in any of the tissues from both species. Furthermore, the ChE activity was almost completely suppressed following incubation with eserine and with the specific inhibitor BW284C51 in all tissues from both species. In vitro exposure to chlorpyrifos promoted a significant decrease in ChE activity in both species. Furthermore, the ChE activity was completely suppressed following incubation with carbofuran and chlorpyrifos. These results suggest that the major ChE forms present in tissues of both crab species show intermediate structural properties and activity patterns, halfway between classic acetylcholinesterase and pseudocholinesterases. However, the sensitivity of the found forms towards ChE inhibitors was established, and the responsiveness of such forms towards common anti-ChE chemicals was established. Both tested species seem to be promising test organisms to be used in marine and coastal scenarios of putative contaminations by anti-ChE chemicals, considering the here reported patterns of response.

Touch-sensitive bristles on the carapace of the mud crab Scylla paramamosain may be receptors for courtship signals

Bristle patches on the carapace behind the eyes were found for the first time in both males and females of the four species of mud crab Scylla spp. Electrocardiography revealed that the bristle patches of Scylla paramamosain were sensitive to touch (with a glass capillary) but not to chemical stimulation (with sugarcane juice). To elucidate the function of these touch signals, the courtship behaviour of S. paramamosain was video-recorded in a broodstock tank. A male approached a female, extended a walking leg over her carapace, touched her bristle patches with a dactyl, mounted her, and probed the bristle patches further with the third maxillipeds. Touch stimulus may be a signal for courtship in Scylla and one of the chain stimuli for the completion of mating behaviour.

Reference gene and tropomyosin expression in mud crab Scylla olivacea, Scylla paramamosain and Scylla tranquebarica.

Tropomyosin, a muscle tissue protein is a major allergen in most of shellfish including mud crab. Quantitative real time-PCR (qRT-PCR) using a stable reference gene is the most sensitive approach to produce accurate relative gene expression that has yet to be demonstrated for allergenic tropomyosin in mud crab species. This study was conducted to identify the suitable reference gene and tropomyosin expression in different body parts of local mud crabs, Scylla olivacea, Scylla paramamosain and Scylla tranquebarica. Myosin, 18S rRNA, GADPH and EF1α were selected as candidate reference genes and their expression was measured in the abdomen, walking leg and cheliped tissues of local Scylla spp. The expression stability was analyzed using the comparative delta-Ct method, BestKeeper, NormFinder and geNorm then comprehensively ranked by RefFinder algorithm. Findings showed that EF1α was the most suitable reference gene across three mud crab species. Meanwhile, the abdomen, walking leg and cheliped selected their own suitable reference gene either Myosin, 18S rRNA, EF1α or GADPH. Overall, tropomyosin was the highest in S. tranquebarica, whereas the least was in S. paramamosain. Interestingly, tropomyosin was the highest in the abdomen of all mud crab species. This is the first analysis on reference genes selection for qRT-PCR data normalization of tropomyosin expression in mud crab. These results will provide more accurate findings for further gene expression and allergen analysis in Scylla spp.

Camouflage by the masking crab,Notomithrax ursus(Herbst, 1788) (Decapoda: Brachyura: Majidae): is it a decorator or a dressmaker?

AbstractMany spider crabs attach various kinds of living material to camouflage themselves and thereby escape detection by predators. This strategy uses a suite of co-evolved characters including a pyriform carapace shape, long agile chelipeds, hooked setae and a stereotyped behaviour pattern which is used to gather and plant pieces of other organisms amongst hooked setae on their body. Notomithrax ursus (Herbst, 1788) is a New Zealand majid crab that lives amongst seaweeds and mainly masks itself with the same. In doing so, it uses all the skills that we expect of a dressmaker. Denuded of its mask, the crab chooses algae it can manipulate, measures and cuts each piece, passes them to its mouth, and then plants them on its body in a roughly regular order, such that the severed ends are inserted into the hooked setae with only intact end visible. Longer pieces are planted on the body and smaller pieces on its walking legs to make a profile resembling a clump of seaweed. Distribution of the seaweed follows the distribution of the hooked setae on the crab. The number of pieces attached is independent of crab size and, as carapace width increases, the crabs compensate by cutting out longer pieces of seaweed. Cheliped allometry explains scaling of the mask. Total length of seaweed used can range 0.6–2.6 m (mean 1.36 m). Increasing mask load is accompanied by increases in the number and size of hooked setae thereby strengthening attachment. The behaviour of N. ursus should be called “dressmaking” not “decorating.” It uses a stereotyped behaviour pattern to follow a design, dictated by the distribution of hooked setae, and produce a customized garment concealing it from predators. A hypothesis on the evolution of masking, from passive to active camouflage is proposed, based on the original ideas of C.W.S. Aurivillius.

Why “swimming crabs” are able to swim – The importance of the axial skeleton: A comparison between the “swimming crab” Liocarcinus depurator and two other brachyuran crabs (Cancer pagurus, Carcinus maenas) using μCT and 3D-reconstruction

Most brachyuran crabs use their pereiopods as walking legs, but there are also a number of species, in which the last (5th) pair of pereiopods (P5) are specialized to permit a unique mode of swimming. One of these P5-swimming crabs is Liocarcinus depurator, commonly found on European shores. We present 3-dimensional μCT-based reconstructions of the axial skeletons and 5th pereiopods (P5), including the intrinsic and extrinsic musculature of the P5, of L. depurator and of two other non-swimming brachyuran crabs, Cancer pagurus and Carcinus maenas. In Liocarcinus, we also present a reconstruction of the 4th pereiopod (P4) together with its intrinsic musculature. We further use 3-dimensional prints of the reconstructed P5 coxa and basi-ischium of L. depurator as well as thoracal parts near the thoracal−coxal arthrodial cavity to build a model which can simulate the effects of muscular activity based on muscle insertions in our 3D reconstruction and under various simulated tensile vectors. This enables us to test muscular functions that had previously been speculated upon. Reconstructed morphological structures are compared to find differences that may explain why of the three species, only L. depurator is able to swim. Significant differences between Liocarcinus and the non-swimmers Cancer and Carcinus were found in the shape of the axial skeleton, external P5 morphology and the dimensions and origin sites of the extrinsic P5 musculature, but not in the intrinsic musculature of the P5. Inclination angle measurements of P1 thoracal−coxal articulation axes against P5 axes showed that in Cancer and Carcinus, angles in the longitudinal plane were smaller than in the lateral one, whereas in Liocarcinus, they were greater. Inclination angles in the longitudinal plane were also much greater in Liocarcinus than in Cancer and Carcinus. 3D print muscular activity simulation showed that muscles inserting at the basi-ischium, which are often referred to as “levator” or “depressor” muscles, may actually also function as promotors or remotors, depending on the tensile vector within which the muscle is acting.

Ultrastructure of chemosensory tarsal tip-pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae).

While chemical communication has been investigated intensively in vertebrates and insects, relatively little is known about the sensory world of spiders despite the fact that chemical cues play a key role in natural and sexual selection in this group. In insects, olfaction is performed with wall-pore and gustation with tip-pore sensilla. Since spiders possess tip-pore sensilla only, it is unclear how they accomplish olfaction. We scrutinized the ultrastructure of the trichoid tip-pore sensilla of the orb weaving spider Argiope bruennichi-a common Palearctic species the males of which are known to be attracted by female sex pheromone. We also investigated the congener Argiope blanda. We examined whether the tip-pore sensilla differ in ultrastructure depending on sex and their position on the tarsi of walking legs of which only the distal parts are in contact with the substrate. We hypothesized as yet undetected differences in ultrastructure that suggest gustatory versus olfactory functions. All tarsal tip-pore sensilla of both species exhibit characters typical of contact-chemoreceptors, such as (a) the presence of a pore at the tip of the sensillum shaft, (b) 2-22 uniciliated chemoreceptive cells with elongated and unbranched dendrites reaching up to the tip-pore, (c) two integrated mechanoreceptive cells with short dendrites and large tubular bodies attached to the sensillum shaft's base, and (d) a socket structure with suspension fibres that render the sensillum shaft flexible. The newly found third mechanoreceptive cell attached to the proximal end of the peridendritic shaft cylinder by a small tubular body was likely overlooked in previous studies. The organization of tarsal tip-pore sensilla did not differ depending on the position on the tarsus nor between the sexes. As no wall-pore sensilla were detected, we discuss the probability that a single type of sensillum performs both gustation and olfaction in spiders.

Efficacy of core decompression with bisphosphonates and Prolotherapy compared with core decompression alone and core decompression with bisphosphonates in the management of avascular necrosis of hip joint

Background: Avascular necrosis (AVN) of hip joint or femoral head is complex disease with complete collapse of the femoral head. Core decompression is the mainstay treatment for grade I and II AVN of hip joint but the results were controversial. In this backdrop, the present study was undertaken to evaluate the combination of core decompression with bisphosphonates and prolotherapy in the treatment of AVN of hip joint. Methods: 36 patients who were diagnosed with for grade I and II AVN of hip joint were recruited and they were divided into three groups (n=12). The patients in three groups were treated with core decompression alone, core decompression with bisphosphonates and core decompression with bisphosphonates, prolotherapy. The patients were followed at 6th month, after 1 year and 2 years respectively. Their outcomes and range of motion were recorded at each follow-up.Results: The outcome of the study shows that the combined treatment of core decompression with bisphosphonates, prolotherapy showed fair outcome at the end of 2 year follow up with effective pain reduction during walking, squatting and cross leg. Meanwhile, core decompression alone and core decompression with bisphosphonates showed poor and good outcome. Conclusion: Thus in patients with grade I and II AVN of hip joint combination of core decompression with bisphosphonates, prolotherapy would be effective in prevention of collapse and pain reduction.

The Eophreatoicus Nicholls, 1926 species flock from Kakadu and Arnhem Land, with a description of a new genus of Amphisopidae (Crustacea : Isopoda : Phreatoicidea).

We present descriptions of 28 new species of Amphisopidae from Arnhem Land and Kakadu National Park of Australia's Northern Territory. We identified five additional species that are not yet fully characterized and are not provided with formal species recognition. This is the first taxonomic treatment highlighting the high species richness within the Phreatoicidea that occur in Australia and likely elsewhere. We document each species fully with scanning electron and light micrographic images, diagnoses, detailed descriptions, keys to identification and justification of each species using parsimony analysis of their morphological and genetic characters. The distributional data show that all species, except for one, have microendemic distributions, with some sibling species occurring within a few kilometers of each other. Because of the age of this group of species, they appear to have spread throughout the region of the Arnhem sandstone plateau and then back-colonized the same habitats so that as many as three morphologically and genetically distinct species may co-occur syntopically. Our research has uncovered a new genus-level taxon of the family Amphisopidae, Kakadubeh gen. nov. This new genus is unlike Eophreatoicus, not only in its general appearance, but also in having an inferred reproductive strategy different from most of the other members of the family. While Eophreatoicus species have males that are much larger than the females and practice precopula, a form of pre-insemination mate guarding, males of the new species, Kakadubeh rangemyahwurd sp. nov., are much smaller than females. In addition, males of this species have a fourth walking leg that is not specialized for holding females, suggesting that they have a reproductive strategy that does not involve precopula of the form seen in Eophreatoicus and Eremisopus Wilson Keable, 2002a. Most of our research has been undertaken in Kakadu National Park, although recent collections have been made in Arnhem Land, yielding additional distinctive species. Given the size of unexplored territory around the Arnhem Plateau and the geographic frequency of discovering new species, we predict that the diversity of this group in the Northern Territory may be many more than the ~35 species described here. At this time, these microendemic isopods appear to be unthreatened by human activities, largely owing to the environmental protection afforded by Kakadu National Park and Arnhem Land, and their cryptic habits during the dry season. Because they are dependent on small springs of permanent groundwater, future changes in hydrology owing to water use and climate change, as well as invasive introduced species, may present risks to populations and species.

Ordovician trilobites with soft parts in African West Gondwana, European peri-Gondwana and Avalonia: a review

Abstract A review of all currently known Ordovician trilobites with soft parts described or figured from West-Gondwana, European peri-Gondwana and Avalonia shows remains of the digestive system in 19 species. In comparison, remains of antennae and/or walking legs are known only in five species. Soft parts are known in Asaphidae, Bathycheilidae, Calymenidae, Cheiruridae, Dalmanitidae, Harpidae, Lichidae, Nileidae, Odontopleuridae and Trinucleidae. Exceptionally preserved trilobites originate from the Late Tremadocian Mílina Formation and Fezouata Shale, Middle Darriwilian Šárka and Llanfallteg formations, early Sandbian Tafilalt and Letná Konservat-Lagerstätten and Katian Bohdalec Formation. Levels containing exceptionally preserved trilobites in these units are characterized by prevailing fine-grained sediments with the exception of the Early Sandbian Lower Tafilalt and Letná Lagerstätten.

Effects on walking performance and lower body strength by short message service guided training after stroke or transient ischemic attack (The STROKEWALK Study): a randomized controlled trial

Objective: To evaluate whetherdaily mobile-phone delivered messages with training instructions during three months increase physical activity and overall mobility in patients soon after stroke or transient ischemic attack. Design: Randomised controlled trial with intention-to-treat analyses. Setting: University hospital. Data collection from November 2016 until December2018. Subjects: Seventy-nine patients (mean (SD) age 63.9 (10.4) years, 29 were women) were allocated to either intervention (n = 40) or control group (n = 39). Participants had to be independent (modified Ranking Scale ⩽2) and able to perform the six-minute walking test at discharge from the hospital. Interventions: The intervention group received standard care and daily mobile phone instructional text messages to perform regular outdoor walking and functional leg exercises. The control group received standard care; that is, primary care follow-up. Main measures: Walking performance by six-minute walking test (m), lower body strength by five times chair-stand test (s), the short physical performance battery (0–12 points) and 10-metres walk test (m/s) were assessed at baseline and after three months. Results: The estimated median difference in the six-minute walking test was in favour of the intervention group by 30 metres (95% CI, 55 to 1; effect size 0.64; P = 0.037) and in the chair-stand test by 0.88 seconds (95% CI, 0.02 to 1.72; effect size 0.64; P = 0.034). There were no differences between groups on the short physical performance battery or in 10-metres walking time. Conclusions: Three months of daily mobile phone text messages with guided training instructions improved composite mobility measures; that is, walking performanceand lower body strength. Clinical Trial Registry: The study is registered with ClinicalTrials.gov, number NCT02902367.

Host specificity and microhabitat preference of symbiotic copepods (Cyclopoida: Clausiididae) associated with ghost shrimps (Decapoda: Callichiridae, Callianideidae).

We examined the host specificity of two ectosymbiotic Clausidium Kossman, 1874 copepods (Cyclopoida: Clausiididae) on two co‐occurrence species of host ghost shrimps. Our results revealed that both species of symbiotic copepod demonstrated extremely high host specificity. Moreover, within a single host shrimp species, each symbiont species displayed strong spatial patterns in microhabitat selection on their hosts’ bodies. Clausidium persiaensis Sepahvand & Kihara, 2017, was only found on the host Callianidea typa Milne Edwards, 1837 and almost exclusively within the host shrimp gill chamber, while C. iranensis Sepahvand, Kihara, & Boxshall, 2019 was only found on the host Neocallichirus jousseaumei (Nobili, 1904) and showed extremely strong preferences for the chelae and anterior walking legs. We also found that while the number of symbionts tends to increase with the host size, the two host species differed in the degree of symbiont infestation, with large C. typa hosting approximately 7× as many symbionts as the similarly sized N. jousseaumeia. The mechanisms resulting in the observed differences in infestation levels and microhabitat preferences of clausidium copepods among their hosts, including differences in physiology, burrowing pattern, and host grooming behavior should be further investigated.

Novel design of a family of legged mobile landers based on decoupled landing and walking functions

The lander has made a significant contribution to soft landings and exploration of an extraterrestrial surface. To further expand its detection range and meet the needs of base construction in the future, it is necessary to design a legged mobile lander (LML) that lets the fixed lander walk. In this paper, a decoupled functions synthesis method (DFSM), which means the decoupled landing and walking functions for LMLs, is proposed: it uses separate structures of landing leg (LL) and walking leg (WL) to perform landing and walking functions. The structure of the Chang’e lander’s leg is selected and designed as the LL. The structures of WLs are determined and presented by the Lie group type synthesis method. In accordance with the combination principle, the landing-walking leg (LWL) for LMLs is designed by combining the structures of a LL and a WL. The structures of a family of LMLs are achieved by assembling the same or different structures of legs. Furthermore, the actuated joints are assigned according to the principle for selecting the actuated joint and one case of LWL is selected as an optimized type by the qualitative evaluation. Finally, one leg of LMLs is taken as an example to analyze the properties and abilities during different stages.

Genomic resources and toolkits for developmental study of whip spiders (Amblypygi) provide insights into arachnid genome evolution and antenniform leg patterning

BackgroundThe resurgence of interest in the comparative developmental study of chelicerates has led to important insights, such as the discovery of a genome duplication shared by spiders and scorpions, inferred to have occurred in the most recent common ancestor of Arachnopulmonata (a clade comprising the five arachnid orders that bear book lungs). Nonetheless, several arachnid groups remain understudied in the context of development and genomics, such as the order Amblypygi (whip spiders). The phylogenetic position of Amblypygi in Arachnopulmonata posits them as an interesting group to test the incidence of the proposed genome duplication in the common ancestor of Arachnopulmonata, as well as the degree of retention of duplicates over 450 Myr. Moreover, whip spiders have their first pair of walking legs elongated and modified into sensory appendages (a convergence with the antennae of mandibulates), but the genetic patterning of these antenniform legs has never been investigated.ResultsWe established genomic resources and protocols for cultivation of embryos and gene expression assays by in situ hybridization to study the development of the whip spider Phrynus marginemaculatus. Using embryonic transcriptomes from three species of Amblypygi, we show that the ancestral whip spider exhibited duplications of all ten Hox genes. We deploy these resources to show that paralogs of the leg gap genes dachshund and homothorax retain arachnopulmonate-specific expression patterns in P. marginemaculatus. We characterize the expression of leg gap genes Distal-less, dachshund-1/2 and homothorax-1/2 in the embryonic antenniform leg and other appendages, and provide evidence that allometry, and by extension the antenniform leg fate, is specified early in embryogenesis.ConclusionThis study is the first step in establishing P. marginemaculatus as a chelicerate model for modern evolutionary developmental study, and provides the first resources sampling whip spiders for comparative genomics. Our results suggest that Amblypygi share a genome duplication with spiders and scorpions, and set up a framework to study the genetic specification of antenniform legs. Future efforts to study whip spider development must emphasize the development of tools for functional experiments in P. marginemaculatus.