Tarsal Organ Research Articles

Strange new spiders: on Roddenberryus, a new and unusual caponiid genus (Araneae, Caponiidae)

The new nopine genus Roddenberryus gen. nov. is erected to include in total five species: three new species, R. kirk gen. et sp. nov. (male and female) from Costa Rica, R. spock gen. et sp. nov. (female) from Campeche, Mexico and R. mccoy gen. et sp. nov. (male) from Baja California Sur, Mexico, as well as two species previously misplaced in Caponina Simon, i.e., R. sargi (Pickard-Cambridge, 1899) gen. et comb. nov. from Guatemala and R. pelegrina (Bryant, 1940) gen. et comb. nov. from Cuba. A male specimen reported as C. sargi Pickard-Cambridge from Costa Rica by E. Kritscher (1957) is assigned to Roddenberryus kirk together with one female collected at the same locality. The new genus is characterized by the distally projected endites and a triangular, projected labium, a conformation unique among nopines; also by a triangular, very short, scaly gladius, serrula with interspersed multiple tooth rows, and a tarsal organ with strongly projected margins. Roddenberryus shares with Tarsonops Chamberlin the cracked tarsi and metatarsi, with multiple adesmatic joints intertwined on the cuticle and an unusual internal respiratory system with both posterior tracheae fused in a single trunk.

Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation

Amblypygi have a tropical and sub-tropical distribution and their first of the four pairs of legs, is modified as feelers. Their activity period and dark habitats render visual cues ineffective and they rely on non-visual sensory perception. There is agreement among researchers that the whip spiders invest in olfactory and tactile senses imparted by sensory structures concentrated on the tarsal segment of the first pair of long, well-articulated non-ambulatory legs that are constantly moved in all directions to sample the environment for detecting location of prey, as also for navigating. This is the first attempt to elucidate the sensory structures present on the antenniform legs of the whip spider, Phrynichus phipsoni (Pocock, 1894), collected from the state of Goa, India; using scanning electron micro[1]scope, and paves way for further research on sensory biology of this cryptic arachnid order. The examined specimen generally conforms to the diversity and morphology of sensory assemblage on the antenniform legs reported in other amblypygi species. Sensory structures elucidated include terminal trident tarsal claws, tarsal organ, bristles, porous sensilla, club sensilla, rod sensilla, slit sensilla, trichobothria, plate organ, pit organ and foliate leaf like hairs.

Beyond size: sexual dimorphisms in pholcid spiders

The extreme sexual size dimorphism of some spiders has long attracted the attention of biologists and triggered countless prominent studies on the phenomenon. This, in turn, has resulted in a widespread bias in the view of spider sexual dimorphisms, even in reviews on sexual dimorphism that looked beyond size. The present article challenges this view by exemplarily documenting sexual dimorphisms in a single family of spiders, the Pholcidae. It offers a comprehensive overview of sexual dimorphisms in this group, derived from the taxonomic literature. Sexual dimorphisms occur in the prosoma (ocular area, clypeus, sternum), abdomen, chelicerae, legs, sensory organs (setae, tarsal organs), and in colouration. In addition, this review provides a rough and conservative estimate of the number of independent origins of sexual dimorphisms in Pholcidae, based on published morphological and molecular phylogenies and character mapping; more than 120 independent origins are hypothesized. The first general conclusion is that spiders show a wealth of sexual dimorphisms beyond size, even in a family that is virtually absent from the general literature on spider sexual dimorphism. The second conclusion is that the taxonomic literature should be more widely appreciated as a rich source of information, not just as a provider of names. However, much of this information is not easily extracted from taxonomic papers. It is primarily the responsibility of taxonomists to do that.

Predatory behavior and sensory morphology of the whip spider Charinus asturius (Arachnida: Amblypygi)

Assessing information about prey before attacking is crucial for predators. Whip spiders (Arachnida, Amblypygi) are predatory arachnids that prey mainly on arthropods and whose first pair of legs concentrates many sensory structures. Nonetheless, these aspects of amblypygid biology have been mostly studied in a few species of Phrynidae and basic information about predatory behavior and sensory morphology remain scarce for other families. In this study, we described the sensory morphology of the antenniform leg and the predatory behavior of Charinus asturius Pinto-da-Rocha, Machado and Weygoldt, 2002, a representative of the family Charinidae. We report the presence of most sensilla types described in the better studied Phrynidae and highlight novel aspects such as the morphology of the tarsal organ and the reduced number of rod sensilla. Our behavioral results underscore the importance of antenniform legs in the predatory behavior of C. asturius. Finally, we suggest new avenues to advance the knowledge about the importance of antenniform legs for capturing living prey.

Evolution of a sensory cluster on the legs of Opiliones (Arachnida) informs multi-level phylogenetic relationships

AbstractPhylogenetic relationships in Opiliones (Arachnida) at the suborder level have greatly stabilized in recent years, largely due to advances in molecular systematics. Nonetheless, identifying morphological characters in the context of well-resolved phylogenies is essential for testing new systematic hypotheses and establishing diagnostic markers. Here, we investigate with SEM a promising character system across Opiliones: the sensilla on the distalmost article of legs I and II. We identified four discrete characters and scored species of nearly all families of Laniatores (28 families, 44 species), three Dyspnoi, two Eupnoi and two Cyphophthalmi. Using a phylogenetic backbone compiled from recent and ongoing phylogenomic studies, we trace the evolution of these sensilla using ancestral state reconstruction. We discover a widespread occurrence of three sensilla (a pair of sensilla basiconica and one hooded sensillum) on the anterior legs of all families of Laniatores studied, and that comparable structures occur in the other suborders of Opiliones. Our analysis shows that this sensory field provides diagnostic information at different levels of phylogenetic relationships. We discuss the implications of the widespread occurrence of these sensilla in Opiliones, which have recently been hypothesized as hygro-/thermoreceptors and their putative homology with tarsal organs in Arachnida.

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.

An Update of the Goblin Spider GenusBirabenellaGrismado, 2010 (Araneae: Oonopidae), with the Description of Three New Species

Fil: Piacentini, Luis Norberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina

Taxonomic Revision of the Jumping Goblin Spiders of the GenusOrchestinaSimon, 1882, in the Americas (Araneae: Oonopidae)

ABSTRACT The genus Orchestina Simon is distributed worldwide and is characterized by having an enlarged fourth femur with which these species are capable of jumping. The genus is also characterized by having a well-sclerotized sperm duct, a near H-shaped arrangement of the eye group, a 4-4-3-3 pattern of raised receptors on the tarsal organs of the legs I–IV, respectively, and by lacking spines on all the legs. All these characters, together with molecular evidence, support the monophyly of the genus, as well as its placement as sister group of Oonopinae. Most American species of Orchestina inhabit the forest foliage and canopy, but in unforested areas they also occur in shrubs and grasses. In this work, we revise the American representatives of Orchestina in a comprehensive context for the first time. In the past, six species were known from the Americas: five from the United States and only one from South America, described from Venezuela. After the study of the principal collections of the world and se...

Survey of cuticular structures on leg IV of cosmetid harvestmen (Opiliones: Laniatores: Gonyleptoidea)

The legs of laniatorean harvestmen feature a considerable diversity of setae, glandular openings, sensory structures, and tubercles. In this study, we compared the morphology of cuticular structures occurring on leg IV of 12 species of cosmetid harvestmen and six species of other gonyleptoidean harvestmen representing the families Agoristenidae, Gonyleptidae (three subfamilies), and Stygnidae. Our results indicate that there is considerable interspecific variation in rough pit glands and the tarsal perforated organ among cosmetid and gonyleptoidean harvestmen. We also found interspecific variation in the relative size, number, distribution, and morphology of the tubercles on the femur, patella and tibia. We observed relatively little interspecific variation in the morphology of sensilla chaetica, trichomes, spines, single pores, tarsal aggregated pores, and slit sensilla. Additional studies of the ultrastructure of cuticular structures, especially rough pit glands, are needed to assess their functional significance. Future systematic revisions of cosmetid taxa may also benefit from the inclusion of characters based upon interspecific variation in the microanatomical structures of the legs.

Redescription of Tapinesthis inermis (Araneae, Oonopidae), with detailed information on its ultrastructure

Tapinesthis inermis Simon, 1882, the only species in the genus, is widely distributed in western Europe. This redescription provides the first information on the ultrastructure of the species using SEM. The morphology of the spinnerets, tarsal claws and tarsal organs, and the internal structure of the female genitalia and the male palp are described and illustrated in detail. The combination of these structures is very similar to those encountered in some dysderoid spiders and supports the basal placement of Tapinesthis among Oonopinae. The phylogenetic relationships of the species are discussed. The only female among the three syntypes is designated as the lectotype.

Comparative Study of the Microanatomy of Four Species of Harvestmen (Opiliones, Eupnoi)

AbstractMost species descriptions of harvestmen from Central America that belong to the suborder Eupnoi are based on characters such as total body length, relative size of leg segments, coloration of the body and legs, and armature of the eye mound and dorsal scutum. Characters based on reproductive morphology and microanatomical structures are generally absent from most taxonomic works. Not surprisingly, the taxonomy of these harvestmen from this region requires extensive revision. In an effort to identify novel characters, we used scanning electron microscopy to compare the morphology of somatic and reproductive structures of Prionostemma vittatum (Roewer, 1910), Metopilio niger (Goodnight and Goodnight, 1942), and Metopilio ornatipes (Banks, 1909). Specifically, we investigated the morphology of the ocularium, ozopore, dorsal scutum, genital plate, pedipalp, spiracular opening on tibia II, ovipositor, and penis. We compared the morphology of these Neotropical taxa with that of a temperate sclerosomatid species, Leiobunum formosum (Wood, 1870). In general, we observed interspecific variation in the surface texture of the cuticle and the distribution of setae on the body and appendages. Potentially informative characters include cuticular structures associated with the ocularium, anterior propeltidium, meso- and metapeltidium, dorsal scutum, genital plate, pedipalp, and penis. We also observed intersexual variation with respect to morphology of Spicer's tarsal organ and the claw of the pedipalp.

The main evolutionary trends in sensory organs and questing behavior of Parasitiform ticks and mites

Studies of sensory organs in ticks and mites of the order Parasitiformes by methods of electron microscopy and electrophysiology started in Russia in the middle of the 1970s due to the activity of Prof. Balashov and with his personal participation. A review of the data accumulated since that time allowed tracing the main evolutionary trends in the morphology of the main composite sensory organs (palpal and tarsal organs of mites, Haller’s organ of ticks, and eyes). Close association between the evolution of questing behavior and the evolution of sensory organs is demonstrated.

Redescription of Female Laelaps nuttalli Hirst, 1915 (Acari: Dermanyssoidea: Laelapidae) with Emphasis on Its Gnathosoma, Sense Organs and Pulvilli.

The present scanning electron microscopic (SEM) study includes the redescription of female Laelaps nuttalli with emphasis on its gnathosoma and pulvilli which were rarely described in superfamily Dermanyssoidea. Chaetotaxy of dorsal shield revealed 40 pairs of setae, 22 on prosoma and 18 on opisthosoma. Epigynial plate carried 4 pairs of setae. Gnathosoma consisted of long basis capituli carrying median hypostome and 2 lateral pedipalps. Hypostome had dorsal labrum of 2 lobes covered with minute papillae, 2 lateral 3-segmented chelicerae, and ventral labium carrying 2 median lobes with laciniae and 2 lateral club-like lobes. Function of labrum papillae might be chemosensory while labium lobules might be mechanical, preventing solid material from entering the oral cavity. Palpal and foreleg tarsal organs comprised 10 and 15 sensilla, respectively. Sensilla of palpal organ were mostly chemoreceptors while those of tarsal organ were probably mechanoreceptors. Each pulvillus terminated with 2 medioventral claws and integumental folds beside longitudinal folds.

The harvestman tarsus and tarsal flexor system with notes on appendicular sensory structures in laniatores

The tarsal flexor system, a novel system of retinacular structures, is described for the first time based on morphological and ultrastructural examinations of several Neotropical harvestmen (Opiliones: Laniatores). The tarsal flexor system is made up of many individual pulleys that function to maintain close apposition between the tendon and internal ventral surface of the cuticle in the tarsus. Pulley cells are specialized tendinous cells that form the semi-circular, retinacular pulley system in the tarsus; these cells contain parallel arrays of microtubules that attach to cuticular fibers extending from deep within the cuticle (i.e., tonofibrillae). The tarsal flexor system is hypothesized to provide mechanical advantage for tarsal flexion and other movements of the tarsus. This system is discussed with regards to other lineages of Opiliones, especially those that exhibit prehensility of the tarsus (i.e., Eupnoi). Comparing tarsal morphology of laniatorid harvestmen to other well-studied arachnids, we review some literature that may indicate the presence of similar tarsal structures in several arachnid orders. The general internal organization of the tarsus is described, and ultrastructural data are presented for a number of tarsal structures, including sensilla chaetica and the tarsal perforated organ. Sensilla chaetica possess an internal lumen with dendritic processes in the center and exhibit micropores at the distal tip. With respect to the tarsal perforated organ, we found no ultrastructural evidence for a sensory or secretory function, and we argue that this structure is the result of a large pulley attachment site on the internal surface of the cuticle. A small, previously undocumented muscle located in the basitarsus is also reported.

Basibulbus, a Hard-Bodied, Haplogyne Spider Genus from Chile (Araneae, Dysderoidea)

A new genus, Basibulbus, is established to contain some seldom-collected, hard-bodied, haplogyne spiders from Chile. Because of their small size and the heavily scutate abdomen of males, these animals resemble gamasomorphine goblin spiders (Oonopidae), but differ in having a heavily sclerotized sperm duct within the male palp and a normal sperm opening in the epigastric furrow. Their tarsal organs lack both the longitudinal ridge and the serial dimorphism in raised receptor number that are considered synapomorphic for oonopids, but are elevated (albeit only at their proximal end), and the genus is therefore assigned to the Orsolobidae. Three new species are described: B. malleco (the type species) and B. concepcion from central Chile (regions VIII and IX), and B. granizo from further north (Region V). Only one other hard-bodied orsolobid genus has been described (Duripelta Forster from New Zealand); Basibulbus does not seem to be closely related to that genus, and represents another in the long list of relictual, phylogenetically significant, Chilean spider taxa. One of the possible synapomorphies of dysderoids, an oblique unsclerotized strip on the base of the anterior lateral spinnerets (which has been lost in higher gamasomorphines) has apparently been lost independently within Basibulbus. That character is present in B. granizo but absent in at least B. malleco.

Microstructure of the tarsal adhesive organs in the bark beetle Ips acuminatus, and their implication as external carriers of pathogens

Ips acuminatus is a common group of bark beetles that infest and damage pine and spruce trees. As a part of research for controlling this insect pest, the adhesive organs on the tarsal appendages were examined using field emission scanning electron microscopy (FE-SEM) to reveal the microstructural characteristics of its biological attachment system. In addition, we also demonstrate their ability to act as external carriers of pathogens. This bark beetle has a characteristic attachment apparatus to move both smooth and rough surfaces. The claws are connected with a pretarsal segment, and their apical diverged hooks are developed to hold rough substrates; however, landing on smooth surfaces is achieved by means of three groups of hairy tarsal pads. The adhesive pads are basically composed of the flattened tip setae usually with a spatula-shaped endplate. Although this bark beetle did not have mycangial cavities, yeast-like spores were concentrated at the invaginated surface of legs where cuticular hairs are densely packed. In particular, the base stalk of the adhesive pad had a sufficient space to accept spores during the dynamic movement of tenent setae.

Reification, Matrices, and the Interrelationships of Goblin Spiders

In a recent review of the interrelationships of goblin spiders (the family Oonopidae), Platnick et al. (2012) presented a new subfamily-level classification of the family, replacing older arrangements that included at least one paraphyletic group. That analysis was based heavily on new evidence obtained, by an international consortium of researchers, through scanning electron microscopy of the tarsal organs, tiny chemoreceptors found near the tips of the legs and pedipalps.

Tarsal Organ Morphology and the Phylogeny of Goblin Spiders (Araneae, Oonopidae), with Notes on Basal Genera

Based on a survey of a wide variety of oonopid genera and outgroups, we hypothesize new synapomorphies uniting the Oonopidae (minus the South African genus Calculus Purcell, which is transferred to the Orsolobidae). The groundplan of the tarsal organ in Oonopidae is hypothesized to be an exposed organ with a distinctive, longitudinal ridge originating from the proximal end of the organ, and a serially dimorphic pattern of 4-4-3-3 raised receptors on legs I–IV, respectively. Such organs typify the diverse, basal, and ancient genus Orchestina Simon. Several other genera whose members resemble Orchestina in retaining two plesiomorphic features (an H-shaped, transverse eye arrangement and a heavily sclerotized, thick-walled sperm duct within the male palp) are united by having tarsal organs that are partly (in the case of Cortestina Knoflach) or fully capsulate (in the case of Sulsula Simon, Xiombarg Brignoli, and Unicorn Platnick and Brescovit). The remaining oonopids are united by the loss of the heavily sclerotized palpal sperm duct, presumably reflecting a significant transformation in palpal mechanics. Within that large assemblage, a 4-4-3-3 tarsal organ receptor pattern and an H-shaped eye arrangement seem to be retained only in the New Zealand genus Kapitia Forster; the remaining genera are apparently united by a reduction in the tarsal organ pattern to 3-3-2-2 raised receptors on legs I–IV and by the acquisition of a clumped eye arrangement. Three subfamilies of oonopids are recognized: Orchestininae Chamberlin and Ivie (containing only Orchestina; Ferchestina Saaristo and Marusik is placed as a junior synonym of Orchestina), Sulsulinae, new subfamily (containing Sulsula, Xiombarg, Unicorn, and Cortestina), and Oonopinae Simon (containing all the remaining genera, including those previously placed in the Gamasomorphinae). The type species of Sulsula and Kapitia, S. pauper (O. P.-Cambridge) and K. obscura Forster, are redescribed, and the female of S. pauper is described for the first time. A new sulsuline genus, Dalmasula, is established for Sulsula parvimana Simon and four new species from Namibia and South Africa.

Continuous Tonic Spike Activity in Spider Warm Cells in the Absence of Sensory Input

The warm cells of the spider tarsal organ respond very sensitively to low-amplitude changes in temperature and discharge continuously as the rate of change in temperature reaches zero. To test whether the continuous tonic discharge remains without sensory input, we blocked the warm cell's receptive region by Epoxy glue. The activity continued in this situation, but its dependence on temperature changes was strongly reduced. We interpret this to mean that the warm cells exhibit specific intrinsic properties that underlie the generation of the tonic discharge. Experiments with electrical stimulation confirmed the observation that the warm cells persist in activity without an external drive. In warm cells with blocked receptive region, the response curves describing the relationship between the tonic discharge and the level of depolarization is the same for different temperatures. In warm cells with intact receptive region, the curves are shifted upward with rising temperature, as if the injected current is simply added to the receptor current. This indicates a modulating effect of the receptor current on the tonic discharge. Stimulation causes a change in the tonic discharge rate and thereby enables individual warm cells to signal the direction in addition to the magnitude of temperature changes.

FIRST ULTRASTRUCTURAL OBSERVATIONS ON THE TARSAL PORE ORGAN OF PSEUDOCELLUS PEARSEI AND P. BONETI (ARACHNIDA, RICINULEI)

Abstract Due to their relative rareness and restricted distribution, little is known about the ultrastructure of ricinuleids. In particular, sense organs have not been the subject of electron microscopic research until now. Ricinuleids use their forelegs to explore their surroundings with tentative movements. The distal tarsomeres of legs I and II of two cavernicolous Mexican species, Pseudocellus pearsei from the Yucatan Peninsula and Pseudocellus boneti from Guerrero, were examined in this study with light microscopy, scanning (SEM) and transmission electron microscopy (TEM). A conspicuous feature of the distal tarsomeres of legs I and II is a single circular opening that extends as a deep tube-like pit into the tarsus. This pore organ is lacking in the 6-legged larvae. Comparable organs are present in Araneae, Scorpiones, Amblypygi and Anactinotrichida. The tarsal organs of the mentioned groups possess several types of sensilla (olfactory, thermo- and hygrosensitive and mechanosensitve). The pore organ...