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.     

Organization of the spinnerets and spigots in the orb web spider,Argiope bruennichi (Araneae: Araneidae)

Although the basic taxonomic characteristics usually remain unchanged, some spinning apparatuses undergo consistent adaptive variations. As the presence of additional protuberances known as nubbins and tartipores have caused disagreements regarding some Araneidae spiders, more detailed definitions on the cuticular structures have recently been proposed. Reflecting this definition, microstructural organization of silk spinning apparatuses in the orb web spider Argiope bruennichi were reconsidered using field emission scanning electron microscopy. Among the seven kinds of functional spigots in females, it was revealed that two types (major ampullates and pyrifoms) are located on anterior spinnerets and another five types are distributed on median (minor ampullates, tubuliforms and aciniforms) or posterior (tubuliforms, flagelliforms, aggregates and aciniforms) spinnerets, respectively. In addition to functional spigots, cuticular remnants of the nubbins and the tartipores were found on the spinning fields, but the number of tartipores on each spinneret varied among individuals based on maturity. Nevertheless, three kinds of cuticular protuberances of ampullate silk glands were clearly visible at both the anterior and median spinnerets.     

Appendage patterning in the South American bird spider <Emphasis Type="Italic">Acanthoscurria geniculata</Emphasis> (Araneae: Mygalomorphae)

Pattern formation by the genes dachshund (dac), Distal-less (Dll), extradenticle (exd) and homothorax (hth) in spider appendages has been studied previously only in members of the higher spiders (Araneomorphae). In order to study the diversity and conservation of pattern formation in spiders as a whole, we studied homologs of these genes in embryos of the bird spider Acanthoscurria geniculata, which belongs to the Mygalomorphae, a more primitive spider group. We show that the patterns of dac and Dll are largely conserved in all spiders studied so far. We find a duplication of hth and exd genes as previously identified in the higher spider Cupiennius salei. These data suggest that pattern formation shows little diversity in all spiders, including the duplication of hth and exd that likely occurred before the split of Mygalomorphae and Araneomorphae. We also find that the legs and pedipalps bear endites of which only the pedipalpal endite expresses Dll and is retained in the adult. Similarly, the limb buds of the posterior spinnerets express Dll and become segmented appendages in the adult, whereas the anterior spinnerets lack Dll expression and are absent in postembryonic stages. In both cases, the expression of Dll or the lack of it indicates structures which will be retained as adult traits or rudimentary structures that degenerate, respectively. The presence of embryonic rudiments of leg endites in Acanthoscurria and the leg-like pattern formation in the posterior spinnerets are interpreted as primitive traits that have been lost in the Araneomorphae.     

The pedipalp of Pseudocellus pearsei (Ricinulei, Arachnida) - ultrastructure of a multifunctional organ

Ricinulei possess movable, slender pedipalps with small chelae. When ricinuleids walk, they occasionally touch the soil surface with the tips of their pedipalps. This behavior is similar to the exploration movements they perform with their elongated second legs. We studied the distal areas of the pedipalps of the cavernicolous Mexican species Pseudocellus pearsei with scanning and transmission electron microscopy. Five different surface structures are characteristic for the pedipalps: (1) slender sigmoidal setae with smooth shafts resembling gustatory terminal pore single-walled (tp-sw) sensilla; (2) conspicuous long, mechanoreceptive slit sensilla; (3) a single, short, clubbed seta inside a deep pit representing a no pore single walled (np-sw) sensillum; (4) a single pore organ containing one olfactory wall pore single-walled (wp-sw) sensillum; and (5) gustatory terminal pore sensilla in the fingers of the pedipalp chela. Additionally, the pedipalps bear sensilla which also occur on the other appendages. With this sensory equipment, the pedipalps are highly effective multimodal short range sensory organs which complement the long range sensory function of the second legs. In order to present the complete sensory equipment of all appendages of the investigated Pseudocellus a comparative overview is provided.     

Evolution of the chelicera: a dachshund domain is retained in the deutocerebral appendage of Opiliones (Arthropoda,Chelicerata)

The proximo‐distal axis of the arthropod leg is patterned by mutually antagonistic developmental expression domains of the genes extradenticle, homothorax, dachshund, and Distal‐less. In the deutocerebral appendages (the antennae) of insects and crustaceans, the expression domain of dachshund is frequently either absent or, if present, is not required to pattern medial segments. By contrast, the dachshund domain is entirely absent in the deutocerebral appendages of spiders, the chelicerae. It is unknown whether absence of dachshund expression in the spider chelicera is associated with the two‐segmented morphology of this appendage, or whether all chelicerates lack the dachshund domain in their chelicerae. We investigated gene expression in the harvestman Phalangium opilio, which bears the plesiomorphic three‐segmented chelicera observed in “primitive” chelicerate orders. Consistent with patterns reported in spiders, in the harvestman chelicera homothorax, extradenticle, and Distal‐less have broadly overlapping developmental domains, in contrast with mutually exclusive domains in the legs and pedipalps. However, unlike in spiders, the harvestman chelicera bears a distinct expression domain of dachshund in the proximal segment, the podomere that is putatively lost in derived arachnids. These data suggest that a tripartite proximo‐distal domain structure is ancestral to all arthropod appendages, including deutocerebral appendages. As a corollary, these data also provide an intriguing putative genetic mechanism for the diversity of arachnid chelicerae: loss of developmental domains along the proximo‐distal axis.     

Patterning mechanisms and morphological diversity of spider appendages and their importance for spider evolution

The prosoma of spiders bears different gnathal (labrum, chelicerae, pedipalps) and locomotory appendages (legs). In most species these appendages are also used for additional functions, e.g. sensing, mating, and courtship. The opisthosoma is equipped with four pairs of highly specialized appendages. Two pairs of spinnerets are used for silk production and manipulation. The other two pairs of appendages are internalized during development and give rise to a complex respiratory system of book lungs and tracheae. Thus spiders have a number of different appendage types with radically different adult morphologies. Furthermore, all these appendage types display significant additional species specific diversity correlating with a large spectrum of functions of the appendages. Despite this importance of appendage diversity for the evolution of the spiders we know relatively little about the genetic patterning mechanisms producing this diversity of morphology. We review recent advances concerning the developmental genetics of spider appendage diversification, mainly concentrating on open questions and future directions of research. We conclude that the deeper understanding of appendage development and diversity in spiders can contribute significantly not only to evolutionary developmental biology, but also to behavioral biology, speciation research and population genetics, and the study of sexually dimorphic traits.     

Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments

The pycnogonids (or sea spiders) are an enigmatic group of arthropods, classified in recent phylogenies as a sister-group of either euchelicerates (horseshoe crabs and arachnids), or all other extant arthropods. Because of their bizarre morpho-anatomy, homologies with other arthropod taxa have been difficult to assess. We review the main morphology-based hypotheses of correspondence between anterior segments of pycnogonids, arachnids and mandibulates. In an attempt to provide new relevant data to these controversial issues, we performed a PCR survey of Hox genes in two pycnogonid species, Endeis spinosa and Nymphon gracile, from which we could recover nine and six Hox genes, respectively. Phylogenetic analyses allowed to identify their orthology relationships. The Deformed gene from E. spinosa and the abdominal-A gene from N. gracile exhibit unusual sequence divergence in their homeodomains, which, in the latter case, may be correlated with the extreme reduction of the posterior region in pycnogonids. Expression patterns of two Hox genes (labial and Deformed) in the E. spinosa protonymphon larva are discussed. The anterior boundaries of their expression domains favour homology between sea spider chelifores, euchelicerates chelicerae and mandibulate (first) antennae, in contradistinction with previously proposed alternative schemes such as the protocerebral identity of sea spider chelifores or the absence of a deutocerebrum in chelicerates. In addition, while anatomical and embryological evidences suggest the possibility that the ovigers of sea spiders could be a duplicated pair of pedipalps, the Hox data support them as modified anterior walking legs, consistent with the classical views.Supplementary material is available for this article at and is accessible for authorized users.Guest editors Jean Deutsch and Gerhard Scholtz     

The spinnerets and epiandrous glands of spiders

The spinnerets of spiders are carried on the fourth and fifth segments of the abdomen (opisthosoma). Primitively there are two pairs, anterior lateral ( al ) and anterior median ( am ) on the fourth segment, and two pairs, posterior lateral ( pl ) and posterior median ( pm ) on the fifth, am are present in Liphistius but are never functional. In mygalomorphs am are invariably absent, and usually al also. In araneomorphs am are either reduced to a function-less colulus, perhaps absent altogether, or represented by the cribellum, which is a specialized spinning organ.
It seems unlikely that the lateral and median spinnerets correspond to the exopodites and endopodites of a biramous limb, which limbs are characteristic of the Crustacea, a group having no close relationship to the Arachnida. From embryology it seems clear that the lateral spinnerets are the segmental appendages. Glands, here described as the epiandrous glands, very similar to spinning glands, occur on the second abdominal segment of most male spiders. It is suggested that these may be serially homologous with the median spinnerets, which would then not be appendicular in origin but would be modifications of ventral glandular structures.     

Microstructure of the silk spigots of the green crab spider Oxytate striatipes (Araneae: Thomisidae)

The genus Oxytate L. Koch, 1878 comprises a homogeneous group of nocturnal crab spiders that have silk apparatuses even though they do not spin webs to trap prey. We examined the microstructure of the silk spinning apparatus of the green crab spider Oxytate striatipes, using field emission scanning electron microscopy. The silk glands of the spider were classified into three types: ampullate, pyriform and aciniform. The spigots of these three types of silk gland occur in both sexes. Two pairs of major ampullate glands send secretory ductules to the anterior spinnerets, and another two pairs of minor ampullate glands supply the median spinnerets. In addition, the pyriform glands send ductules to the anterior spinnerets (45 pairs in females and 40 pairs in males), and the aciniform glands feed silk into the median (9–12 pairs in females and 7–10 pairs in males) and the posterior (30 pairs in both sexes) spinnerets. The spigot system of O. striatipes is simpler and more primitive than other wandering spiders: even the female spiders possess neither tubuliform glands for cocoon production nor triad spigots for web‐building.     

一些蜘蛛类群味觉毛的形态、数量和分布

化学通讯是蜘蛛最基础和最普遍的种内及种间通讯方式之一,蜘蛛体表的味觉毛能够接触性地或者近距离地感知环境中的化学物质,但味觉毛的相关研究仅在少数几种蜘蛛中有过报道。我们通过扫描电镜分别对幽灵蛛科(Pholcidae)、弱蛛科(Leptonetidae)、泰莱蛛科(Telemidae)、蟹蛛科(Thomisidae)和球蛛科(Theridiidae)共5科32种蜘蛛味觉毛的形态、数量及分布进行了观察。结果显示:蜘蛛味觉毛一般呈"S"形或弧形;毛根部与体表形成较大角度,末端开口。一般分布在步足的跗节和后跗节,一些种类在步足胫节亦有味觉毛分布。所观察的蜘蛛中绝大部分种类在触肢上未发现味觉毛,仅有2种蟹蛛即角红蟹蛛(Thomisus labefactus)和膨胀微蟹蛛(Lysiteles inflatus)以及1种球蛛即鼬形微姬蛛(Phycosomamustelinum)在触肢上有味觉毛。味觉毛的数量在不同蜘蛛种类中有较大差异,从十几根到上百根不等。蜘蛛味觉毛的形态、数量和分布等特征除了与遗传相关外,亦有可能与其生境和生活方式等有关。     

Sperm transfer and mating in Ricinoides hanseni (Ricinulei: Arachnida)

Ricinuleid reproduction involves indirect sperm transfer using the highly modified distal podomeres of the third legs of the male. This is homologous with the apparatus and technique used by male spiders, which possess elaborate pedipalps. The interpretation of the method of sperm transfer is based upon morphological studies of the male's third legs and the female's genital atrium and the behaviour of males during mating. The male charges the emboli of his modified leg tarsi with sperm from his penis. After climbing on to the back of a receptive female he delicately and precisely places a modified tarsus in the genital atrium of the female. A series of lobes on the tip of part of the modified tarsus fit into a number of vesicular evaginations of the female's genital atrium. The lobes form part of the mechanism which provides a firm attachment of the male's tarsal elements with the female's genital atrium during sperm transfer. A tubular element of the modified tarsus fits into a spermatheca of the female. Sperm and seminal fluid are then injected from the male's embolus into the female's spermatheca.     

Embryonic expression patterns of Wnt genes in the RTA-clade spider Cupiennius salei

Spiders represent widely used model organisms for chelicerate and even arthropod development and evolution. Wnt genes are important and evolutionary conserved factors that control and regulate numerous developmental processes. Recent studies comprehensively investigated the complement and expression of spider Wnt genes revealing conserved as well as diverged aspects of their expression and thus (likely) function among different groups of spiders representing Mygalomorphae (tarantulas), and both main groups of Araneae (true spiders) (Haplogynae/Synspermiata and Entelegynae). The allegedly most modern/derived group of entelegyne spiders is represented by the RTA-clade of which no comprehensive data on Wnt expression were available prior to this study. Here, we investigated the embryonic expression of all Wnt genes of the RTA-clade spider Cupiennius salei. We found that most of the Wnt expression patterns are conserved between Cupiennius and other spiders, especially more basally branching species. Surprisingly, most differences in Wnt gene expression are seen in the common model spider Parasteatoda tepidariorum (a non-RTA clade entelegyne species). These results show that data and conclusions drawn from research on one member of a group of animals (or any other organism) cannot necessarily be extrapolated to the group as a whole, and instead highlight the need for comprehensive taxon sampling.     

Microstructure of the silk apparatus of the comb-footed spider, Achaearanea tepidariorum (Araneae: Theridiidae)

The microstructural organization of the silk‐spinning apparatus of the comb‐footed spider, Achaearanea tepidariorum, was observed by using a field emission scanning electron microscope. The silk glands of the spider were classified into six groups: ampullate, tubuliform, flagelliform, aggregate, aciniform and pyriform glands. Among these, three types of silk glands, the ampullate, pyriform and aciniform glands, occur only in female spiders. One (adult) or two (subadult) pairs of major ampullate glands send secretory ductules to the anterior spinnerets, and another pair of minor ampullate glands supply the median spinnerets. Three pairs of tubuliform glands in female spiders send secretory ductules to the median (one pair) and posterior (two pairs) spinnerets. Furthermore, one pair of flagelliform glands and two pairs of aggregate glands together supply the posterior spinnerets, and form a characteristic spinning structure known as a “triad” spigot. In male spiders, this combined apparatus of the flagelliform and the aggregate spigots for capture thread production is not apparent, instead only a non‐functional remnant of this triad spigot is present. In addition, the aciniform glands send ductules to the median (two pairs) and the posterior spinnerets (12–16 pairs), and the pyriform glands feed silk into the anterior spinnerets (90–100 pairs in females and 45–50 pairs in males).     

虎纹捕鸟蛛体表扫描电镜观察

对虎纹捕岛蛛(Ornithoctonus husoena)的眼、生殖球、颚叶、听毛、触毛、琴形器、跗节器、发音器、幼蛛及成蛛的纺绩器和螯肢等结构进行了扫描电镜观察。     

Spinneret Microstructure of the Silk Spinning Apparatus in the Crab Spider, Misumenops tricuspidatus (Araneae: Thomisidae)

The silk spinning apparatus in the crab spider, Misumenops tricuspidatus was studied with the field emission scanning electron microscope (FESEM) and the main microstructural characteristics of the silk glands are presented. In spite of the fact that the crab spiders do not spin webs to trap a prey, they also have silk apparatus even though the functions are not fully defined. The crab spider, Misumenops tricuspidatus possesses only three types of silk glands which connected through the typical spinning tubes on the spinnerets. The spinning apparatus of Misumenops closely corresponds to that of wandering spiders such as jumping spiders or wolf spiders except some local variations. Anterior spinnerets comprise 2 pairs of the ampullates and 48 (±5) pairs of pyriform glands. Another 2 pairs of ampullate glands and nearly 20 (±3) pairs of aciniform glands were connected on the middle spinnerets. Additional 50 (±5) pairs of the aciniform glands were connected on the posterior spinnerets. The aggregate glands and the flagelliform glands which have the function of sticky capture thread production in orb‐web spiders as well as the tubuliform glands for cocoon production in females were not developed at both sexes of this spider, characteristically.     

Morphology and Differentiation of Non-sensory Cuticular Structures in Mysidacea, Cumacea and Tanaidacea (Crustacea, Peracarida)

The non-sensory cuticular structures of some peracarideans (Mysidacea, Cumacea, Tanaidacea) were examined by scanning electron microscopy. The various types of structures present in the adult specimens are listed and the relation amongst them is elucidated. Three ways of differentiation of the structures can be distinguished: 1) a differentiation in the complexity of the structures themselves, 2) a differentiation of their arrangement on the body. 3) a differentiation of their distribution on the various parts of the body. A highly differentiated type of arrangement (row) of a number of simple structures (e.g. teeth) may lead to a higher complex structure (comb), which is seen to be developed best on special regions of the body (e.g. the distal segments of thoracic legs). The function of the cuticular structures–by analogy with other taxonomic groups–is discussed.     

Epimorphosis and repair processes of schistomelic pedipalps and walking appendages in <Emphasis Type="Italic">Tegenaria atrica</Emphasis> (Araneae,Agelenidae)

Experimental studies of regeneration and repair processes of schistomelic walking legs and pedipalps in the early postembryonal stages of Tegenaria atrica were carried out in two parts. In the first part changes in the structure of appendages were produced by exposing the developing embryos to alternating temperatures (14 and 32°C, changing every 12 hours) as teratogenic factor. In the second, principal, part of studies after amputating a given fragment of a larval schistomelic appendage the appearance, then the growth and development of the external regenerates were observed. The completion of epimorphosis of the pedipalps followed at nymph IV stage (after four post-larval moults) that of the walking appendages in most cases at nymph V stage (after five post-larval moults). In control spiders repair processes were noted, which proceeded at a rate comparable to regeneration processes.     

Central projections of cheliceral mechanoreceptors in the spider Cupiennius salei (Arachnida,Araneae)

Central projections of lyriform organs and tactile hairs on the chelicerae of the wandering spider Cupiennius salei were traced using anterograde cobalt fills. Different fibers arising from both mechanoreceptor types arborize in the cheliceral ganglia, which are part of the tritocerebrum, and in sensory longitudinal tracts in the center of the suboesophageal nerve mass together with afferent fibers arising from mechanoreceptors on the walking legs and the pedipalps. This convergence of sensory projections in the sensory longitudinal tracts might provide the anatomical basis for the coordination of the movements of different extremities during prey capture and feeding. The findings also support the hypothesis that the tritocerebrum originally was a preoral ganglion in spiders. © 1993 Wiley-Liss, Inc.     

拟环纹豹蛛雄蛛触肢上黑白相间毛饰物的功能

狼蛛科雄蛛附肢上多样化的饰装往往与求偶行为相偶联,这些特殊的饰装通常被认为是雌性选择的结果。拟环纹豹蛛Pardosa pseudoannulata,属狼蛛科豹蛛属,雄蛛触肢胫节密被白毛,跗舟密被黑毛,具有典型的性二型现象;同时,只有成熟的雄蛛才展现触肢黑白相间的毛饰物。推测拟环纹豹蛛雄蛛触肢这种黑白相间的毛饰物可能在物种识别中具重要作用。在室内我们拟通过涂抹操作对拟环纹豹蛛雄蛛触肢黑白相间毛饰物的功能进行分析。实验分为4组,分别是对照组(A组,雄蛛不做任何处理)、雄蛛触肢白色胫节全部涂成黑色(B组)、雄蛛触肢黑色跗舟全部涂成白色(C组)和雄蛛触肢的黑色跗舟被涂成黑色(D组),然后采用雌雄配对进行求偶交配行为测定。实验结果表明,B组雄蛛的交配成功率显著低于A、C和D组的雄蛛,而后3组雄蛛的交配成功率无显著差异。相反,B组雄蛛被雌蛛相食百分率显著高于其它3组。可见拟环纹豹蛛雄蛛触肢上黑白相间毛饰物,尤其是其胫节上的白色饰物在雌蛛种间识别中起重要作用。