The external morphology of the pseudoscorpion Roncus andreinii

The external morphology of the four postembryonic instars of Roncus andreinii (di Caporiacco, 1925) is described and compared with one of the related R. lubricus L. Koch, 1873 (Gabbutt & Vachon, 1967), with particular emphasis on disposition of the chelal trichobothria in relation to growth.
From the evaluation of characters it is concluded that a few morphometric and chaetotaxic characters (i.e. the length, ratio and shape of pedipalpal articles, the ratio of fingers/pedipalpal hand, the chaetotaxy of sternites II and III) represent good specific discriminants, while the relative position of trichobothria along the chelal axis is nearly the same in both species.
The localization of the growing and non-growing regions along the pedipalpal fingers may be of practical use in the search for new taxonomic characters.     

Evidence for air movement signals in the agonistic behaviour of a nocturnal arachnid (order Amblypygi)

Many arthropods possess filiform hair sensilla (termed trichobothria in arachnids), which are extremely sensitive detectors of medium particle displacement. Electrophysiological evidence in some taxa suggests that these sensilla can detect air particle displacements resulting from intraspecific communication signals. However, it has not yet been shown for any species that the air particle displacements detected by the filiform hairs are themselves perceived as a 'signal' (i.e. that individuals make behavioural decisions based upon the responses of these organs to the displays of conspecifics). We investigate the agonistic behaviour of the whip spider Phrynus marginemaculatus and the role of its trichobothria in receiving agonistic signals. Whip spiders have extremely elongated 'antenniform' first legs, which they vibrate close to their opponents during agonistic interactions, inducing air movements that excite their opponents' trichobothria. We find that ablation of the trichobothria causes significant increases in: (I) contest duration, and (II) the probability of contest escalation past aggressive displays to physical fighting. Therefore, in the absence of air movement-sensitive sensilla, contest assessment is impaired. This suggests that whip spiders exploit true air movement signals during agonistic interactions, and that these are received by the trichobothria. Furthermore, these results indicate that, in whip spiders, such signals help mitigate the cost of agonistic interaction.     

THE EXTERNAL MORPHOLOGY OF TWO PSEUDOSCORPIONS NEOBISIUM CARPENTERI AND NEOBISIUM MARITIMUM

All stages of Neobisium carpenteri and N. maritimum are described and compared. Details are given of the chaetal counts, measurements, ratios and morphological characters which can be used to distinguish the species. These are compared with the corresponding stages of N. muscorum (Gabbutt & Vachon, 1965). A study of the positions of the trichobothria, on the fingers of the chelae of the three species, during successive stages, indicates the approximate place at which the increments are added at the moults. The different positioning of these growth zones results in disparities in the disposition of the trichobothria in the adult condition. The importance of the relative positions of the trichobothria, as well as the stage at which certain trichobothria first appear, are discussed briefly in relation to the systematics of this order.     

Fine Structure of the Trichobothria and their Regeneration during Moulting in the Whip Scorpion Typopeltis crucifer Pocock, 1894

Abstract The highly complicated structure of the trichobothrium in the whip scorpion Typopeltis crucifer (Uropygi, Arachnida) has been reconstructed from ultra-thin serial sections. The spatial positions of two trichobothria on the first pair of legs, as well as their innervation by several dendrites point to an effective spatial localization of stimulus sources. Numerous cells are involved in the regeneration of the trichobothrium during moulting. They can be classified according to their position and function in forming the sensillum: there are 11 sensory cells, four inner envelope cells, about 21 trichogen cells and numerous outer envelope cells, including tormogen cells. The complicated cell pattern is compared to conditions in similar sensilla of other arthropods in terms of function and phylogeny.     

Testing compatibility between molecular and morphological techniques for arthropod systematics: a minimally destructive DNA extraction method that preserves morphological integrity, and the effect of lactic acid on DNA quality

Three practical aspects related to the preservation and destruction of DNA and/or morphological characters of spiders were examined: potential morphological damage during non-destructive DNA extraction was assessed by counting trichobothria, a fragile sensorial feature found on spider legs; the effect on yield of non-destructive DNA extraction; and whether possible DNA degradation is caused by residues of lactic acid, which is used as a temporary mounting medium for the study of morphological structures in spiders and insects. Destructive extractions yielded higher amounts of DNA than non-destructive methods. However, non-destructive methods yielded usable amounts of DNA while leaving delicate trichobothria intact. Of the non-destructive extractions, a longer digestion period (36 h vs. 12) yielded higher amounts of DNA and did not damage trichobothria. Lactic acid did not induce short-term DNA degradation or inhibit PCR reactions, even at high concentrations. These results show compatibility between molecular and morphological requirements without compromising DNA quality or specimen integrity.     

Agonistic signals received by an arthropod filiform hair allude to the prevalence of near-field sound communication

Arthropod filiform hairs respond to air particle movements and are among the most sensitive animal sensory organs. In many species, they are tuned to detect predators or prey and trigger escape or prey capture behaviours. Here we show for the first time that these hairs also receive intraspecific near-field sound signals in an arachnid. During agonistic encounters, whip spiders (Arachnida, Amblypygi) perform antenniform leg vibration (ALV) displays that have significantly longer duration in contest winners than losers. During an ALV display: (i) the vibrating antenniform leg of the displaying whip spider is positioned close to the trichobothria (filiform hairs) on its opponent's walking legs, (ii) the vibrating antenniform leg can excite these trichobothria via air movements and without direct contact, (iii) the antenniform leg of the displaying whip spider vibrates at a frequency that causes particularly strong, sustained excitation and little adaptation in the trichobothria, and (iv) the duration of an ALV display can be extracted from the response of a trichobothrium. Since filiform hairs are widespread among arthropods, communication via such hairs could be extremely prevalent.     

The release of attack and escape behavior by vibratory stimuli in a wandering spider (Cupiennim salei keys.)

Summary The wandering spiderCupiennius salei responds to vibration of the substrate either with predatory behavior (approach) or with a startle reaction or escape behavior (withdrawal) (Fig. 3). The effects of different parameters of the signal in releasing this behavior were studied by applying various artificial stimuli to a spider standing on a vibrating platform with one or more legs. Receptors sensitive to substrate vibration and the trichobothria, which respond to airborne vibration, together determine the response. Spiders without trichobothria: The type of response to vertical vibrations isfrequency-dependent (Fig. 4a), with predatory reactions predominant at low frequencies (3–4 Hz), and withdrawal reactions at high frequencies (350–460 Hz). Whereas approach is most likely to occur at an intermediate, frequency-dependentamplitude, the probability of withdrawal increases continuously with increasing amplitude (Fig. 6). With sine wave stimuli the lowest threshold amplitude for approach is 9 m peak-to-peak (550 Hz, range tested 1–550 Hz) whereas that for withdrawal is 17 m (800 Hz, range tested 1–800 Hz). The threshold for approach is lower by 6–8 dB whenband-limited noise is used, and the probability of an approach response increases as the bandwidth is expanded. The threshold curve for withdrawal, however, is the same in all cases (Fig. 4b and 5). The spider is capable of both frequency and amplitude discrimination.The metatarsal and pretarsal slit sense organs contribute to these responses as is shown by increased thresholds following their destruction (Fig- 7). Intact animals, with functional trichobothria as well as slit sense organs: They have lower thresholds for withdrawal (by ca. 10 dB; Fig. 9) and shorter reaction times than do spiders without trichobothria. Unlike animals without trichobothria the amplitude thresholds of intact animals to bandlimited noise are ca. 7.5 dB lower than those to sine wave stimuli. The approach threshold is the same as that of spiders without trichobothria. According to direct observation the trichobothria are deflected by airborne sound generated by the substrate motion; the deflection angle increases with both amplitude and frequency of substrate vibration (Fig. 10).There is acentral nervous interaction between the signals from the trichobothria and the slit sense organs with the following basic properties: when both of the two receptor systems receive either a prey-like stimulus or a stimulus eliciting withdrawal their effects add, but when the trichobothria receive stimuli unlike prey they inhibit the approach reaction that would otherwise be triggered by substrate vibration.     

蜘蛛听毛的电镜观察

选用新蛛类的9种蜘蛛作为研究的对象，通过听毛的电镜观察探讨听毛在不同类群的差异。研究结果表明：管网蛛科的北京马蹄蛛的毛窝和听毛显然与中纺类，原蛛类和新蛛类中其他科的种类均不相同。拟壁钱科的居室拟壁钱（有筛器蜘蛛）和北国壁钱（无筛器蛛蛛）的毛窝和听毛的结构相差悬殊，很难看出亲缘上的关系，刺瓣似隙蛛和机敏漏斗蛛的毛窝差别大，无法表明它们之间近缘，园蛛科和肖蛸科种类的听毛窝和听毛数目表明两者之间近缘。     

First record of the mygalomorph spider family Paratropididae (Arachnida,Araneae) in North America with the description of a new species of Paratropis Simon from Mexico,and with new ultramorphological data for the family

A new species of the genus Paratropis is described from North America: Paratropis tuxtlensis sp. n., from a tropical rainforest in Veracruz, Mexico. This is the fifth Paratropis and the tenth paratropidid species described and the first North American record of this Neotropical family. The species is described based on adult males and females, and juveniles. The juveniles show ontogenetic variation in the number of cuspules on the labium and endites, and in the number and position of leg trichobothria. This is the second Paratropis species, and the third paratropidid known from both sexes. The scanning electron photographs (SEM) reveal new morphological data and contribute to the knowledge of the family.     

The sensory equipment of a spider – A morphological survey of different types of sensillum in both sexes of Argiope bruennichi (Araneae,Araneidae)

Spiders show a wide range of sensory capabilities as evidenced by behavioural observations. Accordingly, spiders possess diverse sensory structures like mechano-, hygro-, thermo- or chemoreceptive sensilla. As to chemoreceptive structures, only trichoid tip-pore sensilla were found so far that were tested for gustation. That spiders are also able to receive airborne signals is corroborated by numerous behavioural experiments but the responsible structures have not been determined yet. Here, we provide sensilla distribution maps of pedipalps and walking legs of both sexes of the wasp spider Argiope bruennichi whose biology and mating system is well explored. By means of scanning electron microscopy, we scrutinized whether there is in fact only one type of trichoid pore sensillum and if so, if there are deviations in the outer structure of the tip-pore sensilla depending on their position on the body. We also describe the external structure and distribution of slit sense organs, trichobothria and tarsal organs. Our study shows that all four sensillum types occur on pedipalps and walking legs of both sexes. As to chemosensory organs, only tip-pore sensilla were found, suggesting that this sensillum type is used for both gustation and olfaction. The highest numbers of tip-pore sensilla were observed on metatarsi and tarsi of the first two walking legs. Mechanosensitive slit sense organs occur as single slit sensilla in rows along all podomers or as lyriform organs next to the joints. The mechanosensitive trichobothria occur on the basal part of tibiae and metatarsi. Tarsal organs occur on the dorsal side of all tarsi and the male cymbium. The distribution maps of the sensilla are the starting point for further exploration of internal, morphological differences of the sensilla from different regions on the body. Cryptic anatomical differences might be linked to functional differences that can be explored in combination with electrophysiological analyses. Consequently, the maps will help to elucidate the sensory world of spiders.     

Fine structure of antennal mechanosensilla of adult Rhodnius prolixus stål (Hemiptera: Reduviidae)

Each antenna of both sexes of adult Rhodnius prolixus has approximately 570 mechanosensitive neurons that innervate five morphologic types of cuticular mechanosensilla: campaniform sensilla, tapered hairs, trichobothria, and type I and type II bristle sensilla. Each campaniform sensillum and tapered hair is presumably innervated by one mechanosensitive bipolar neuron and probably functions in proprioception. The campaniform sensilla being located at the base of the scape could monitor the position of the antenna. Tapered hairs are found at the distal margin of flagellar segment I and projecting laterally from the bases of the pedicel and scape. They probably provide information about the relative positions of the antennal segments. Seven trichobothrium are located on the pedicel and three on flagellar segment I. Each trichobothrium has a long filamentous hair inserted into the base of a socket that extends inwardly as a cuticular tube and is innervated by one bipolar neuron with a tublar body, a parallel arrangement of microtubules associated with electron-dense material. The trichobothria may respond to small variations in air currents. Type I bristles occur at the base of the antenna and are the most numerous type of mechanosensillum; an average of 452 occur on each antenna of females and 440 on males. The bristle is curved toward the antennal shaft and is serrated distally. Type II bristles are located distally and are the second most numerous type of mechanosensillum; an average of 88 were counted on each antenna of females and 94 on males. The type II bristle is straight with small, longitudinal, external grooves and projects laterally from the antennal shaft. Each type I and II bristle sensillum is innervated by a bipolar neuron whose dendrite is divided into an inner and outer segment. The outer segment is encased by a dendritic sheath which may be highly convoluted and distally contains a tubular body. Two sheath cells are associated with each sensillum. Both types of bristle sensilla have a tactile function. The tubular bodies of both types of bristle sensilla have a complex structure indicating that they are very sensitive. Variations in the amount and arrangement of the electron-dense material at the tip of the tubular bodies may reflect differences in viscoelastic properties that underlie functional characteristics.     

Central nervous projection patterns of trichobothria and other cuticular sensilla in the wandering spider Cupiennius salei (Arachnida,Araneae)

Summary Central projections of mechano-and chemoreceptors on the legs and pedipalps of the wandering spider Cupiennius salei were traced by anterograde cobalt fills. The primary afferent fibres from trichobothria, tactile hairs, lyriform organs and contact chemoreceptive hairs enter the leg ganglia and pedipalpal ganglia ventrally. On their way through these ganglia there is very little arborization. The main areas of arborization are in the sensory longitudinal tracts in the suboesophageal nervous mass. The central projections of all mechano-and chemoreceptors examined show somatotopic organization. Sensilla located proximally on the legs are represented in dorsally located sensory longitudinal tracts, whereas those located on distal leg segments enter more ventral tracts. The afferent fibres of receptors of identifical modality on a specific segment of all legs and of the pedipalps overlap in the same tracts. No indication for a tonotopic arrangement of the trichobothrial afferences was found, which might have been associated with the mechanical frequency tuning of the trichobothria known from other experiments. The convergence of the projections of different types of receptors in the sensory longitudinal tracts is considered to be an anatomical basis for their functional interaction in behaviour. Both the convergence of the projections of receptors from the same segment of different legs and the somatotopy are connectivity patterns possibly associated with the orientation of the spiders towards mechanical or chemical cues.     

The Fine Structure of Trichobothria in Moss Mites with Special Emphasis on Acrogalumna longipluma(Berlese, 1904) (Oribatida,Acari, Arachnida)

Using SEM and TEM techniques, the trichobothria of Acrogalumna longipluma(Galumnidae, Pterogasterina) were studied in relation to a variety of other moss mites. Each sensillum is composed of a mostly solid bothridial seta and a very complex socket, the bothridium. The setal base bends sharply as it passes through the six chambers of the bothridium, which are arranged in an S-shaped configuration. The proximal end of the seta is an elongated oval and inserted into a thin socket membrane provided with radiating suspension fibres. This peculiar shape of the setal base proper and probably also the existence of connecting pieces are assumed to provide directionality to the sensillum. Two differently shaped tubular bodies are found under the setal base, of which only one is in contact with the seta. The tubular bodies are surrounded by peculiar ‘dense tubes’, i.e. derivatives of the dendritic sheath. The rather thick, outer dendritic segments curve through an extensive receptor lymph cavity and terminate with ciliary regions. The inner dendritic segments are only short. Perikarya and axons as well as the enveloping cells do not show any peculiarities. The trichobothria of moss mites most probably represent vibration receptors reacting to substrate and/or air-borne stimuli. The variety of shapes and the complexity, which is not found to this extent in any other arthropod group, are discussed in relation to ecophysiological demands.     

The giant fiber system in the forelegs (whips) of the whip spider Heterophrynus elaphus Pocock (Arachnida: Amblypygi)

Summary The front legs of the whip spider H. elaphus are strongly modified to serve sensory functions. They contain several afferent nerve fibers which are so large that their action potentials can be recorded externally through the cuticle. In recordings from the tarsus 7 different types of afferent spikes were identified; 6 additional types of afferent spikes were discriminated in recordings from the tibia and femur. Most of the recorded potentials could be attributed to identifiable neurons serving different functions. These neurons include giant interneurons and giant fibers from diverse mechanoreceptors such as slit sense organs, trichobothria, and a joint receptor. In the present report these neurons are characterized using electrophysiological and histological methods. Their functions are discussed in the context of the animal's behavior.Abbreviations GN giant neuron - S segment     

Description of the Immatures of Scaptocoris carvalhoi Becker (Hemiptera: Cydnidae)

Nymphs and adults of the burrower bug Scaptocoris carvalhoi Becker feed on vegetal sap of their host plants through the roots, and little is known on the morphology and biology of its immature stage. Therefore, we aimed to characterize the immatures of S. carvalhoi by describing the egg and the morphology of each instar. Eggs of S. carvalhoi have a smooth chorion surface without visible micropylar processes. The presence of five instars was confirmed by the coefficient of determination (R ²?>?0.95) and by the growth constant (K between 1.2 and 1.6). Nymphs have an elliptical body and fossorial scythe-like forelegs. The tarsi are absent as in adults, and the prototarsal insertion region becomes visible only in the fourth instar. Nymphs from first to fourth instar of S. carvalhoi showed the presence of 1?+?1 trichobothria in urosternites III to VII, close to the anterior margin and inside the spiracles; besides these trichobothria, fifth instars presented 1?+?1 pre-trichobothria in urosternites III to V located posteriorly, almost in the row of spiracles close to the posterior margin of the urosternites. This is the first detailed morphological record of immatures belonging to Scaptocoris.     

Prey-capture in a ground-beetle larva

The larvae of the ground beetle Notiophilus biguttatus F. (Coleoptera, Carabidae) feed mainly on hemiedaphic Collembola (springtails). The level of humidity required by the larvae lies between that of their prey and that of the adult beetles, and leads them to places where Collembola are abundant. The larvae are able to detect aggregations of Collembola by means of chemical cues. Visual orientation is of no importance in predatory behaviour: the attack is triggered and directed by contact with a springtail. This contact, by the trichobothria of the head, is too gentle to provoke the Collembola to jump.     

Chelal growth in pseudoscorpions

There is a linear relationship between the successive positions of named trichobothria on the pedipalpal chelae during the course of post-embryonic development of five British pseudoscorpions belonging to the family Neobisiidae. Growth constants calculated from the trichobothrial data are higher than those calculated for the chelal axis. This discrepancy is resolved in terms of a model, based on growing and non-growing regions, which is a good approximation to the data. The extent of these regions is calculated for all stages and differences between the species are noted. The assumptions implicit in the model, its realism and its predictive value are discussed.     

A new high-elevation scorpion species of the genus Scorpiops Peters, 1861 (Scorpiones: Euscorpiidae: Scorpiopinae) from the Himalayas,India

A new high-elevation scorpion species of the genus Scorpiops is described from the Indian state of Himachal Pradesh. Scorpiops spitiensis sp. nov. is the second highest-elevation scorpion species in Asia and the first one from India occurring at elevations above 4200 m. The new species closely resembles Scorpiops petersii, but it can be distinguished from it based on a suit of characters, one of which is the presence of 16 trichobothria on the external aspect of the patella, which is unique to the new species.